Hey everyone, Grzegorz Baran here.
In this video, I am going to present you a turntable setup I use to scan small and medium sized props for photogrammetry reconstruction. If you are interested not just how but also WHY, this should be the video for you. There are two basic strategies when you are shooting for photogrammetry. You can capture the subject by moving your
camera around the object, or you can rotate the object while keeping your camera in fixed position. In both cases our main target is to capture our subject from every possible angle making sure that our images are as sharp and as consistent as possible. Shooting outside isn't an easy job as there are many external factors independent on us. To get the image quality which is useful for photogrammetry reconstruction we need to find a way to compensate at least some of them
what complicates the capture process. There is no much we can do for large, static environment elements like trees, rocks, cliffs or buildings. We have to capture them in their original position and environment.
Hopefully there is no reason to scan small, separate props outdoor and we can bring them to the environment where we fully control the weather, light and capture them there. Since shooting indoor gives us more options to control the capture environment we can try try to use it in our advantage and simplify but also automate the capture process.
This way the capture can be more efficient, but also give us way better quality to what we can get outside. Unfortunately it requires slightly different equipment and approach to outdoor capture and this is the video I made to cover my findings on this subject. So what do we need? First we need a subject of our scan and the camera. Since our main goal is to hold the camera in place while moving the subject we need to mount our camera somehow in locked position
and create a stable and steady platform which can hold the subject and rotate it in 360 degrees. I have found that it is good to have both - the subject and the camera mounted on certain height. This way we get better access to the subject in cases when we need to change the cameras angle for better framing but also get a better visual separation to the background. Photogrammetry software expects the camera to move around the subject.
It means we need to cheat the software somehow so it believes we still move the camera around. And there are a few key factors we need to solve. The first one is the background. Any visible background elements are an obvious information that we don't move the camera around our subject but the subject itself. Since we need to trick the photogrammetry software that its otherwise, we need to remove all the background details from the equation. We usually do that by creating a black and
white mask for each captured image which tells the app what area should be ignored during the photogrammetry reconstruction process and which we want to keep. Manual masking process can take ages, especially when we have hundreds of images to deal with. Fortunately almost each photogrammetry software offers some tools to automate the masking process. Having a static and solid background without any details and color, which contrasts with the subject can make automated masking process really quick and easy. In theory it should be something neutral in grayscale which lacks surface details, but basically to make our life easier the background color should be just black.
Anything bright might cause glares and reflections on any shiny and reflective surfaces we might want to capture. Especially if we plan to use cross-polarisation technique to remove glares and illuminate the prop from the camera direction. It means that the best and the most efficient background color for the prop capture is BLACK, as black color absorbs most of the light, and therefore lacks of any details photogrammetry software might struggle with. The BLACK color also doesn't colorize props by bounced light, which is very useful when we want the color to be accurate. Of course photogrammetry software offers an automated option to remove static background points from the equation but I have found that results are way better if we mask the background out totally. The second thing we need to deal with to trick the software that the camera doesn't move are shadows. Its obvious that if we rotate any prop in any standard lighting the shadows won't follow it. Subtle shadows can be usually mitigated by the photogrammetry software, but strong, direct shadows can cause misinterpretation issues as the photogrammetry software might interpret them as integral part of the surface structure and don't find the match between images. The solution for this is to reduce the indoor lighting and replace it by the light we cast directly from the camera angle. This way the camera never sees any shadows as they are always projected behind the subject from the camera point of view. So in this case, we can clearly see that we rotate the subject with the camera mounted in fixed position at the same time. And even without a background context its still easy to tell that this is the subject which moves. But in here when we removed shadows and background context totally it is not so obvious anymore. There is no any background or lighting context photogrammetry software can relate to, Now we can capture the prop from any direction we want by simply changing its position on the platform and photogrammetry software is going to believe that the prop is floating in void and what moves, is the camera. Another thing we have to deal with is glare and reflections of light projected on objects surface by a light source. Every surface of any object reflects the light to some degree. For those which we consider reflective, the light reflection turns into glare. It causes similar issues to shadows regarding the surface misinterpretation as it follows the light angle. The best and the most efficient way to remove glares, is to use cross polarisation technique. Basically we mount a polarisation filter in front of the camera lens and another one on the light source to polarise it under certain angle. This way we can get the subject illuminated with the polarised light, so we can remove the glare by rotating the polarisation filter mounted on the the cameras lens. Here you can see an example with the apple used as a subject. This is the shot of the apple illuminated with the external light sources. As you can see it has some shadows and some glare coming from the light source. Next lets overwrite the light with the flash light illuminating the subject from the camera point of view. This way we can remove all shadows as all of them are now behind the apple and the camera cant see them anymore. As you can see there is a strong glare caused by the light. Glare can be removed by by rotating the polarisation filter until both polarisation filters cover the same polarisation angle. And this is the result. Pure surface data without any shadows and any glares. There are 2 key subjects worth to understand and apply regarding the distance between the prop, camera and the background but also overall camera setting. These are the Inverse Square Rule and the Depth of Field dependency. These subjects are very useful in any aspect of photography or photogrammetry, not just the prop scanning.
Lets start with the Inverse Square Rule which is the rule of the light falloff. The rule says how the distance affects the light intensity.
Usually people believe that when we double the distance we get half of the light intensity, but it isn't correct. The Inverse Square rule says that the light intensity gets 75% weaker every time it doubles the distance it travels. It means that the light intensity after the distance is doubled drops to 25% for the same coverage area.
And that's two whole stops for the camera. The intensity drop is caused by the light spread. This rule applies to any source of light. Same to the sun and to the candle. A laser beam is an exception as the light is specifically focused but only to some degree. After certain distance the Inverse Square rule applies also to the laser beam. So if we use our gargoyles as a subject and place them in even distance from 1 to 4 meters. And illuminate the light from a bulb which gives us lets say 2000 LUX of light in 1 meter distance, we would see that the second gargoyle placed 2 meters away to the source of light gets only 500LUX, which is 25% of the light power the first one gets which makes him 4 times darker to the first one. The 3rd one placed 3 meters away would get 9 times less light to the first one which is 11%.
The forth one, since we doubled the distance again to the second one, would get 25% of the light intensity the 2nd one has but its 16 times less light intensity compared to what illuminates the first gargoyle. We can apply this rule for prop scanning to define the distance between the light source, the scanning subject and the background. The shorter the distance to the subject, the more light it gets therefore we can shot quicker. The darker the background is, the less distance we actually need to make it invisible. Because if the distance form the light and the camera to the subject is similar as between the subject and the background, we already know that it gets illuminated just by 25% of the light our scanning subject gets. And if the background is black, it usually absorbs over 95% of what it gets. Of course we can increase the distance to the background, which can be very helpful when we scan dark props and the contrast between them and the background isn't significant. But basically by using black background color we don't need a lot of space for our setup. The next very important subject for the photogrammetry is the Depth of Field dependency. The Depth of Field is a distance between closest and farthest objects that appears acceptably sharp in the image. It is the range within which everything we capture appears sharp for the camera. Since for the photogrammetry we dont capture beauty images but pure data, sharpness of this data is a key factor affecting the final reconstruction quality. Our goal is to setup the camera the way, the scanning subject is fully in camera focus.
The sharper the subject is on captured images, the better further reconstruction quality. The distance between the camera and the first element that is considered to be acceptably sharp is called DoF near limit. Similarly, the distance between the camera and the furthest element that is considered to be acceptably sharp is called DoF far limit. The focus point used to focus the camera is called a focal plane. The limits of depth of field are not hard boundaries between sharp and unsharp since defocus is produced gradually. There are 3 key factors which affects the depth of field.
The aperture, focus distance and the focal length. Lets start with the aperture. The aperture is a hole inside the lens which blocks light access. We can control how wide this hole is by changing the F-stop setting. The wider and more open the aperture, the more light gets to the camera sensor but the shallower and more evenly relatively to the focal plane the depth of field will be. With the smaller aperture we get less light hitting the camera sensor but in result we get deeper, proportionally shallower in front to the focal plane and deeper behind the focal plane depth of field With the wider aperture, less light and exposure time is needed to take the image. Smaller aperture has to be compensated with
stronger external source of light or longer exposure time needed to take the picture. This principle also applies to our eyes. If you want you can do a fairly simple experiment and limit the amount of light reaching your eye. Just shape your hand like I do and make sure you block the light and let it pass only through a little gap made with your fingers. Then take a look at something through that gap. It works even if you have a vision defect and wear glasses on a daily basis, just take them off and look through the gap. The smaller the gap and more light you blocked the sharper the image should appear for your eyes. Using this knowledge we need to find the best balance between the depth of field and exposure time to get the sharpest images possible in reasonable amount of time. It is worth to mention that at some point, when the gap is very small we start losing image quality and sharpness again. This physical phenomenon is called a diffraction and cannot be avoided no matter what lens we use. Diffraction is the result of the light dispersion caused by the edges of the apertures hole which scatters the light. The focus distance dependency has a great impact on depth to field and is quite simple to follow: the closer the distance at which we are focusing the lens, marked by a focal plane on a chart, the shallower and more evenly spread is the depth of field.
The further we are from our subject the deeper and unevenly spread the depth of field will be. The focal length, usually represented in millimetres, is the basic description of a photographic lens. The longer the focal length, the narrower the angle of view and the higher magnification. With the longer focal length we can get more orthogonal view and more accurate coverage of the subject for the photogrammetry. The shorter the focal length, the wider the angle of view and the lower the magnification, therefore when shooting from a close range we get less subject coverage as well as bigger perspective distortion. The larger the focal length, the shallower and more evenly spread from the focal plane is the depth of field. So when we shot the subject from the same distance without changing any camera setting except the focal length with the longer one, we will get proportionally shallower depth of field, which will be more evenly spread around the focal plane. With the shorter focal length, the deep of field gets deeper and the distance between the focal plane and both near and far DoF limits gets proportionally uneven. Of course, in practice we need to compensate the change of focal length by changing the distance to the subject the way we can get the most of it from each image but also to make sure when the subject rotates it doesn't get out of the frame. But only by knowing DoF dependencies our choice can be fully conscious and give us the best results we can get. There is one more depth of field dependency I would like to mention, but its more a worth to know fun fact then a rule to apply since the impact it has is really very subtle. Therefore, the depth of field also depends on a cameras sensor size. Full frame camera has slightly shallower depth of field than APS-C cameras at the same effective focal length and aperture. Ok, so since we have the theory covered we can move to the actual scanning setup I built for 3D prop scanning. I already had some photogrammetry equipment I use on a daily basis. I mean things like a camera, tripod or monopod I usually use for outdoor scanning. But while its enough to scan outside there are a few key things missing to build a fully functional indoor setup for 3d props scanning. The most important in my opinion was the light source I could mount on a camera to illuminate the subject and get rid of the shadows. I did some initial research and made quite expensive mistake. Basically I purchased a F&V R300 LED Ring Light.
The first thing I learnt after it arrived was that it had no any useful tripod and camera mount or even a power supply attached. To be honest it had a steel ring mount but it was useless since it blocks access to the lens for polarisation filter when used. So next I ordered a L-Bracket to be able mount the light on a tripod and attach the camera to it. I also had to purchase 2 dedicated batteries and a quick lock plate to be able mount and demount this setup from a tripod in a quick and safe way. A good thing about this R300 is that it has an option to be powered also from AC if needed and overall, gives very strong and stable light when works. Fortunately I didn't purchase any AC adapter.
This LED light gives 2200 LUX in 1 meter range which isn't bad. Also the power of light can be controlled gradually if someone wants to use it for a video blogging or something. To be able to cross polarise the light for 3D scanning I had to mount a polarisation filter in front of this light.
I ordered one on eBay from Germany. Since the radius of the light was bigger then any polarisation sheet offered I contacted the seller and hopefully he was fine to sell me slightly wider polarisation sheet to what offered. To cut the shape matching the light I ordered a simple, plastic circle cutter for paper. When both arrived I cut the shape and mounted it to the LED light with the transparent tape. When do that, be careful as the tape changes the light angle when passing through the tape and gets polarised under slightly different one. In result it might appear as glare as we cannot cut light polarised under two different angles at the same time using single polarisation filter. Anyway, at this point I was ready to start with the actual 3D prop scanning. Initially I scanned on the ground using black foamed mousepad and long focal length to frame the prop on it trying to get a black solid background behind. I used to trigger the shutter with the cable remote every time after I rotated the prop manually. But as you can see it is not the most efficient and well organised way to go. Also due to lack of actual distance to the background there were no background separation and in result I didn't get any decent results with this approach. As an improvement I moved everything up to a higher level. Initially as a platform for prop holding I used the monopod with a tripple leg with the flipped down Wacom pen holder placed on the top. This time as a background I used standard light reflector leaning against the wall, facing with its black side to the camera. This setup gave me better results but the rotation of prop was still done manually therefore was pretty random, uneven and inaccurate. I was never sure if I didn't double the images or angle or left some areas without enough coverage. The stand used to hold the prop was unstable and the props I was scanning kept dropping to the ground during the scanning process. This is why the next thing I was planning to improve was the way to hold and rotate props. Unfortunately the R300 LED light started to break down.
After about 10 scans I have noticed the first led bulb blinking. After a while it died while next two started blinking the same way. The lamp lost its lighting consistency when set below 100% of power but hopefully since it was still covered with the warranty I was hoping to get it fixed. I sent a few emails to the service and to the company itself asking for help but I didn't get a single response from them. After some time I sent a few more emails, this time to different addresses given to me by the Amazon. The Amazon also was trying to contact them but didn't get any response again. Finally, since there was no way to fix it or replace, Amazon offered a full refund.
I wasn't very happy with this option since I invested already in R300 bracket, dedicated batteries and I wasted polarisation sheet to cut a polarisation filter for this lamp. Without the R300 light, all were totally useless for me. The good thing though was that at least I learnt something about LED lights I can share with you. Basically, the lesson learnt is that even a strong led light, has no power to overwrite any outdoor lighting It is to weak even to overwrite supportive ambient light. In practice it means that to use it, the scanning environment has to be almost dark. Also I had to compensate low power of the light with the higher ISO and longer exposure time, not mentioning that this light is to weak to scan anything outdoor, even at night. And last but not least. If I put together the cost of the light with the additional equipment I needed to purchase to make it working, it becomes a pretty expensive to what it offers.
So I decided to send the broken light to Amazon, and get the refund and purchase something better this time. My next choice this time was the AR400 Ring Flash Light. Unlike the R300, this one had a battery, charger, light diffuser and fully functional and high quality camera mount bracket included. The power of LED light AR400 outputs is much lower to the amount of the R300 LED light. Its still enough to set and verify the cross polarisation angle but it isn't not enough for 3D prop capture. But the real difference is that the AR400 isn't just a LED light but its an actual flash light which can output incredible amount of light in a very short amount of time. Here is the comparison showing the power of the AR400 flash light when compared to the LED light power. Since the flash duration in this case is just 1/300 of a second I decreased the video speed so you can see it better. This short duration is what we exactly need for 3D prop capture as this way we can capture images in a very short exposure time. With the maximum flash power, an AR400 outputs enough light to overwrite even a direct sunlight in a sunny day. To check how strong the AR400 really is I took it outside and mounted it on a tripod in position facing to the ground. I also mounted 2 polarisation filters, one on the AR400 ring flash light and one on a camera lens as this is the usual cross polarisation setup. I took an image without the flash to get an environmental lighting reference to compare. Next, with both filters mounted I set the flash to 100% of its power and took another image. As you can see its pretty strong but doesn't overwrite the direct sun from this distance. Next I removed a ring polarisation filter mounted on a flash light and took another image. And another one but this time without any polarisation filters mounted. As you can see, polarisation filters affect the power of light a lot. Of course many depends on the filter quality but roughly each takes the light about 2 f-stops down. But as you see on these images, even with both polarisation filters mounted but the flash set to 100% of its power I was able to fully overwrite the sun light and remove all direct shadows it cast. The problem with flash lights is that each has a limit of continuous images in can take in short bursts. The higher the output power, the less continuous shots we can take.
This limit also applies to AR400 which at 100% of its power can be triggered just 40 times after which the flash light needs at least 10 minutes break to cool down
Since to capture any prop from each side in decent quality we need to take at least 150 images, it means that the only flash power level which makes sense for us is quarter of its power. This is the image taken with both polarisation filters mounted but with just quarter of the power. It is definitely not enough to fully overwrite the direct sun light, but since we know an inverse square rule already, we know that we can increase the power of the light 3 times just by decreasing the distance to the subject by half. Of course since we don't plan to scan any 3D props outdoor it shouldn't be an issue at all. With the led light ring, even as strong like R300 I still had to scan in very dark, indoor environment.
The AR400 even on its quarter power setting allows us to scan indoor in a bright day. To be able to mount the AR400 flash light on a tripod, as well as the camera on a flash light I used two Manfrotto quick lock plates. I have been using them for years and find them a very reliable and handy mounting system They really can make life easier and are strong enough to hold such heavy gear stable under most angles if needed. What I love about these plates is that when used it takes just seconds to mount or unmount the light and the camera from a tripod. Cross-polarisation for 3D prop scanning is a must. In reality almost every surface is reflective to some degree and cross polarisation helps to deal with most of them. It also helps with the background separation as it removes highlights from the background or the prop holder To reduce costs after my failure with the R300 I decided to reuse the polarisation ring I cut already and mount it on AR400. The AR400 has slightly smaller diameter to R300 but it is not flat as R300 was. Literally the glass surface of AR400 is convex what is the problem when we want to mount flat polarisation sheet on it. Anyway I gave it a try and mounted the old polarisation filter to the AR400. Of course since it didnt aligned very well due to curved shape I had to use more scotch tape to keep it in place. The scotch tape slightly changes the polarisation angle when the light passes through it. That means that we can't cut the light passing just throught the filter and the light passing through the tape at the same time and one of these is going to be visible and cast glares. As you can see when we look through polarisation filter we have to make a choice which one do we cut. Of course in this case we need to cut the one which covers the wider area. We can also consider to use opaque tape or try to limit the space the tape covers. It was also a total nightmare to take this filter on and off. Also due to glass curvature it never aligned well enough therefore was exposed to external damage when stored or transported. Following friends advice I decided to make my life easier and purchase a professional polarisation filter from the Scan Space. Since its from a New Zealand it took a while for it to arrive but I can tell that it was a great decision. The filter has magnetic mount which makes mounting, demounting or changing polarisation angle very easy. Also since it was designed to counterfeit the convex shape, the polarisation sheet is flat what gives very even polarisation coverage.
The handle marks the orientation of vertical polarisation angle which makes alignment with the lens mounted polarisation filter very easy, especially if it has a marking on it.
We just need to align the marker with the handle to get maximum cross polarisation power. Unfortunately mine has a 5 degree defect but as long I know it I just need to rotate is slightly. Its also worth to mention that the polarisation filter from the Scan Space reduces the light only by 1.4 f-stops which is a very good and impressive score. Anyway, with the flash light and the polarisation filter covered I still had to find a better solution for the actual prop holder as without it I wasn't able to scan efficient and reliable enough. The initial ideas I tested didn't work very well. To improve them I decided to utilise the screw on the top of the monopod and use it as the rotation centre for simple turntable platform. To keep it cheap I used a jar lid which I filled in with the styrofoam. Since the styrofoam was to soft to keep the platform locked around the screw, to strengthen and stabilise the rotation I used a steel nut .
As the original lid color wasn't very scanning friendly I purchased a black spray to paint it. Unfortunately the paint didnt work very well when combined with the styrofoam and melted it. In result the platform lost intended stability and didn't work. But since I liked the idea with lids I decided to push it forward. To build next version I grabbed two jar lids.
I made a hole with a screwdriver in a bottom of the first one and painted it with the black paint. What I have learnt so far is that its very important to shake the paint can very well to get better paint consistency. The consistency of the paint can be also improved when we keep the paint can in a warm water for a while. I have also learnt that paint coating is much beter when we spray the surface from a larger distance. Next I painted the second lid. It definitely wasnt the best painting, actually it was a really bad one, but it was the first time I painted something this way. When the paint got dry I glued both lids together and repainted them again to cover the glue. This way I also wanted to fix my my previous crappy painting. I painted it a couple times but I never managed to get quality I wanted. The next things about painting I learnt was that multiple paint layers make the painted surface soft and vulnerable to anything sharp or heavy we put on it. The idea itself wasn't bad and this simple turntable worked quite well. I even managed to scan a few things using it but at the end I considered it as another failure. The biggest downside of this approach was lack of stability and rotation accuracy. It was quite decent but since it was based on manual rotation and eyeballed judgement I would consider it as a pretty unreliable solution. Also since the lid surface was flat it wasn't able to hold any rounded props reliably enough and most of fruits or stones I was trying to scan, sooner or later felt to the ground during the scanning process. I did a bit more research and considered a few different turntable solutions but finally I decided to purchase Syrp Genie Mini 2 and Syrp Turntable. A Genie Mini 2 came in a nice, cartoony box. It is a wireless device which rotates around it's core in a very controlled, steady and accurate way. All rotation parameters can be fully controlled through a Syrp app.
To run the app we need a phone or a tablet which can communicate through a Bluetooth. In the turntable mode the app allows us to rotate the device manually or to automate the rotation by allowing us to pick the amount of pictures we want to capture in full 360 turn and the delay between each. After we hit the run button, we can go to get a coffee and come back when full 360 degree capture is over. This device can be used for time-lapses, real-time motion video, multi-rows panoramas, astro time-lapses and turntables. When fully charged the battery last for about 5 hours. The device can be mounted on a standard tripod or monopod screw. It comes with manual, cleaning cloth and some usb to usb-c cables for PC connection.
To get the most from the device, it needs some additional accessories. In my case: a Syrp turntable. The Syrp turntable arrived in similar cartoony case. It contained 2 cartoony detail less rings which can be placed on the turntable if we don't wanna see turntables markings a steel turntable plate covered with markings with the tripod mounting platform attached on its bottom side. To assemble it, the Syrp Genie Mini 2 device has to be mounted between these two parts. The box also contained a cable to connect the device to the cameras remote input port to remotely release the cameras shutter. Unfortunately the cable had no plug that could be plugged into the camera. My guess was that is because each camera type might get a different socket type, but it wasn't something I would expect anyway. To make it working I had to order another cable and wait until it arrives. I took some time searching for the correct one but finally to avoid any additional surprises I decided to order an original C1 Syrp shutter link cable from the original Syrp store which was designed for Canon cameras. This way I was sure that cables are going to match and finally the entire setup is going to work. As I mentioned, one end goes to the long Syrp cable, the other one goes to the camera remote shutter release input. To get the clean background separation I was planning to use the black paper circle. Unfortunately the one which came with Syrp was too reflective for photogrammetry and therefore too visible during the capture. So I decided to order a set of black, mate cartoon sheets and cut the circle using the circle cutter I already purchased.
I cut a few of them but I found them still too reflective and since the surface was flat, there was still nothing really to hold round props steady in place. Since I knew that even mate cartoon is not going to work I decided to introduce a surface which is rough and less reflective and I purchased 2 by 2 meters large piece of black polyester fabric. Using black mate cartoon sheets I shaped the base platform in the centre by creating a kind of concave limiter which I was hoping is going to limit any props movement during the turntable rotation. Next I cut a piece of black fabric and wrapped the cartoony platform from the top. I used scotch tape to hold it in place but it didn't work very well. Cartoon material used was to thin and too elastic and tape didn't hold fabric well enough.
To make the platform stronger, I cut a plywood circle. Next I assembled it together with a cartoon one and added 4 steel pins at the top angled to the centre to increase the holding stability. Finally it was able to hold props like apples in place. I wrapped it with the black fabric and used pins from the bottom to mount it. Unfortunately the pins were too long and they pierced through the plywood. I also found that pins I used in a centre to limit potential prop movement area were too shiny and were visible even through the fabric. So I covered them with a black paint and cut another plywood circle to make the platform thicker. Next I wrapped the platform from the top with a bigger piece of black fabric and used pins to hold it in place. Finally it worked and I made the turntable plate which I was happy with and which one I use so far. This version was able to hold any medium sized round prop in place without any issues. The turntable platform is very useful to scan heavy and less stable props. Bare in mind, that props to be captured from different directions have to be switched to their different side after full 360 rotation pass as this is the only way to get them captured from all around. This approach works the best when the subject is framed from the slightly higher angle, but still the way we don't see the bottom part beneath the turntable. Unfortunately under this angle we always capture part of the turntable surface beneath the prop itself which sometimes covers even half of the image. and since the turntable is at the same distance as the prop, we don't benefit from any DoF based distance separation or light falloff similar to the one we get from the background behind. The platform also gets some background
separation issues when we scan dusty things as they often affect the surface beneath. When the dust drops it seats on the surface and rotates with it. We also might struggle when dealing with very bright objects, which might significantly illuminate the surface beneath with the bounced light. As we know, the light when bounces gets different polarisation angle, and any glare coming from it cannot be stopped by the polarisation filter mounted on a camera lens anymore. Of course its not a tragedy and we can mask things like this out, but its something to keep in mind. The heavy and solid turntable platform makes sense when we plan to scan larger, unbalanced and heavy props. Even if the turntable platform I made also works for lighter round props as they can be held in the centre pretty well, when used we include large part of the turntable in the background. We would benefit from moving small props like an apple away from the turntable and reduce the prop holder coverage on images to the total minimum. This way we would benefit from the background separation the most and have less work with masking later.
Also since this approach gives us better prop exposition we can benefit from more angling options for the camera especially when compared to very limited angles when working with the turntable. This is why I created two additional thin prop holders. One for smaller props and one for slightly larger and heavier. The idea I had was pretty simple and cheap. I have found that I might utilise a simple cardboard tube we can get from a core of toilet paper or aluminium foil rolls. I have found that rolls shape can be very efficient in keeping round things steady in place. I decided to go with the one with the smallest radius because the wider one covered to much of the actual prop at the bottom as props were falling into it. Since the thinnest one was the least stable, to compensate it I decided to glue a small plastic lid at the bottom. Of course the tube had to be black and rough so it consumes all the light instead of bouncing it back so in result appears as black as possible when captured. I could simply paint it but since rough surface should be even less visible I decided to cover it with the fabric.
This time I purchased a set of 10 adhesive velvet fabric sheets. Next I shorten the cardboard tube a bit and wrapped the piece of adhesive velvet fabric around it.
To make sure the base doesn't reflect light in any unwanted way I also decided to cover it from the top with adhesive fabric. So I cut the circle with the circular paper cutter and applied it to the plastic lid from the top. And finally I glued both pieces together. It was a great idea and I managed to get a decent separation to the background when used, unfortunately the adhesive velvet wasn't as black as I was hoping it can be. To get it fixed I sprayed the top part of the holder with a black paint and surprisingly the paint made a really big difference. Now I was able to scan dirty props like this chunk of soil without worrying about soil debris getting into frame. The additional paint cover really appeared to be a great idea as after this the holder became barely visible on captured images. Of course there were no chance this holder is going to hold something heavier like a stone gargoyle or even a larger piece of soil. Since I wanted to have an option to rise heavier props out of turntable level I decided to build something similar but a bit more solid and wider. As a base for next holder I used a metal coffee can. It seemed to be definitely more solid and sturdy solution to cardboard one. I did some measurements to calculate how much material do I need and I cut it from the adhesive velvet fabric. First the top cover and then the side. And here it is. This one was steady enough even to hold a heavy stone gargoyle. Since I already knew it makes the difference, similar to the previous holder I sprayed this one with the black paint. I am still considering to experiment a bit more with paint covers and purchase even a darker black paint to make holders totally invisible during the scanning, but what I managed to get so far seems to work well enough and there are other expenses I need to prioritise first. The best and the most efficient way to scan slender objects is to scan them in vertical position.
Due to depth of field limitations, this is the most efficient and often the only way to keep entire subject in focus. It means that we should never scan slender props this way as we would need to sacrifice a lot trying to increase the depth of the Depth of Field to get the full prop in focus. To cover slender prop from the top or from the bottom, we should rather move the camera up or down to capture it under different angle and focus just on this part doing fool 360 pass around. There is really no way we can get any slender prop into full focus under this angle, especially when it rotates. It means that our prop has to be held steady in vertical position somehow, and this is where the next prop holder comes in handy. The gripper. I didn't even risk trying to build the gripper from a cardboard and I simply ordered one on Amazon. Its main purpose is to hold props as steady as possible for macro photography. It was designed to hold plants, leaves, branches without damaging them but also even small flash lights or light reflectors. Its not strong enough to hold heavy things like a stone gargoyle but works great for large flowers and even light toys. It has a very strong mount grip at one side which can be mounted to the turntable and a fully adjustable but strong and very stable body which is almost invisible when cross-polarised during the capture. I believe that for more complex props It can be combined with another gripper and I can imagine that 3 of them used at the same time might hold the heavy stone gargoyle I have in fixed position. This gripper has a bright, yellow part at the bottom grip which for obvious reasons always has to stay out of the camera frame. It has pretty simple construction and is very easy to use. The top gripper has a foam used to hold delicate props without damaging them. Unfortunately the holding grip is plastic and can open maximum to 2.5 cm in widest part. The holder is black, which is a good thing as it can help with its invisibility when cross polarised but it is a bit shiny and a bit too reflective.
Hopefully the idea behind the holder is to do not have it included in any images if possible. Even if it sometimes is, as long its not the yellow part its still barely visible. I think this holder can be a really good help when used. Its great to hold flowers the way the camera can access them from any angle I don't have any favourite holder as each has its own purpose. I believe the one I use the most is the turntable as its the most I believe it can benefit from darker paint which can absorbs even more light but its something to be tested in a future. At current stage its good enough. This is the image with all 4 holders with the color checker in standard indoor lighting. This is the one illuminated with the flash but without any cross polarisation. This one use distance based background separation and surface based light absorption only.
And this is the image captured with the flash with full cross polarisation. This is the setting usually used for prop scanning. As you can see only the gripper reflects some light but most of it are light bounces from the color checker. But as I mentioned, the gripper is the only one in here which shouldn't be included in most frames as its main function is to expose the prop the way it doesn't have to. The next and very important thing in this setup is the background. Initially I used to use a standard light reflector facing to the camera with its black side.
Unfortunately its surface was a bit too reflective and to wrinkled when used. Since I already purchased a 2 by 2 meters wide piece of polyester fabric I used to cover the light reflector with it. It wasn't anything fancy but it worked pretty well. The black polyester fabric was a really good light absorber. Unfortunately the reflector itself wasn't the best and the most adjustable platform I could use and needed to be replaced with something better. Since it wasn't square, no matter what I did, polyester fabric always got some folds and stretches. The final reason I decided that I need a replacement was lack of its stability. Every time when unfolded it needed to lean against something very stable, otherwise it used to fell to the ground. I ordered a T-shaped portable background backdrop stand as a replacement.
It is not the best and heavy duty stand type but its pretty easy and quick to mount or dismount, its reliable enough and its definitely much better to the previous solution. A good thing about this one is that it doesn't need to be assembled into letter T, which would be way to big to what I need. It can also do the job with a single arm.
It holds the fabric very well and and I use it now all the time. When I was using the R300 ring led light, I just had to simply turn the led light on and start taking images. The camera was connected through the remote shutter release port to the Genie Mini 2 turntable with the cable. And after each revolution the turntable was sending a signal to the camera to release the shutter and camera was taking a picture. After I replaced the R300 ring led light with the AR400 ring flash I realised that now I need to re-trigger the flash light somehow every time the camera takes the picture. Unfortunately the camera I use does not have any socket that I can use to connect the AR400 ring flash with the cable. Also, the AR400 doesn't have any built-in wireless receiver. The solution I had to find was to find a transmitter I could mount on a camera's hot shoe and a receiver I can plug into the AR400 ring flash light. I have found a few compatible with both the AR400 and my camera but I had no clue which one should I get.
Since I didn't know much about flash lights I made a mistake by ordering a Godox FT-16, wireless flash trigger with the small USB receiver. The FT-16 is very simple and doesn't have many options. The transmitter needs to be powered by 2 AA batteries, which were not included in the package. Both, the transmitter and receiver works in 433MHz frequency. It means they are not compatible with other transmitters or receivers working in different frequencies. Each receiver we want to use need to be set to
exactly same group and same channel as the trigger. We do that by setting the group with the knob and channel number with switches. We have a choice of 16 flash groups and 16 channels. In this case, we can set any combination we really want to, as long its being set exactly the same way for the receiver and for the trigger. But in case of use a bit more sophisticated transmitters with full digital screen we need to know what exact number certain combination of switches represents.
To make this setup working we need to plug the receiver to the AR400 USB port and if we turn the ring flesh light ON we can control it remotely through the wireless transmitter. Of course since we want the camera to control the flash we need to mount the transmitter on a cameras hot shoe. Now when we press the shutter release button, we trigger the flash at the same time. Now, with the '+' and '-' buttons on a transmitter we can control the power of the flash. It is worth to mention that AR400 offers 22 steps of precise power control with the flash duration ranging from 1/300 of the second for the highest power setting to 1/10000sec for the lowest one. 1/1 means 100% of power, 1/2 means 50%, 1/4, 25% and it goes down to 1/128 which gives 0.7% of the maximum output power. Since I mentioned already that there is a dependency between power of the flash and the amount of consecutive flashes before heat protection stops the flash. The maximum power setting we should use then is 1/4 which is 25% of its full power. It gives us 200 consecutive flashes in a single series. In this setting the flash, flashes the light in shorter time than 1/300secs which in theory should let us set the shutter around this value. The quickest shutter speed my camera can handle is 1/8000 sec and of course we don't need anything around this value for static objects but I have found that very short shots appears black. I made some additional tests and I quickly realised that something is wrong when I set the shutter speed quicker to 1/300s. This is the shot with shutter speed set to 1/250 of a sec. But this is with 1/350sec. This is with 1/500sec and for 1/1000sec the image appears totally black.
I did some research and I have found that this is the sensor curtain which appears on images when the shutter speed is faster to the sync speed used to trigger the flash. In plain words, the FT-16 trigger I purchased doesn't support high speed synchronization and cant trigger the flash quick enough. The only solution for this is to shot with the longer exposure or get a better flash trigger which offers HSS. I had no other choice then order another trigger, this time the one which supports high speed synchronisation. A new trigger I purchased was Godox XT32C.
Unlike the previous one, this one uses 2.4GHz frequency. It means it is not compatible with the previous receiver, which is fine as the package I ordered included one 2.4GHz receiver. Except the frequency they support, both receivers looks exactly the same, have exactly the same knob for group setting and and switches for channel and USB jingle on their back side. The significant difference is between transmitters. Of course FT-16 works in 433MHz while XT32 2.4GHz. They both are very light, are made from plastic, have very similar weigh, both need to be powered by 2 AA batteries. XT32 has larger, slightly tilted but in my opinion more functional LCD panel. Unlike the FT-16 it has no knob and manual switches for group and channel setting which in this case have to be set using digital buttons and be visualised through LCD screen. XT32 has quite big and really very handy in my opinion dial designed to control the flash power while with the XT-16 we had to press '+' and '-' buttons. But the main and key difference between the old and the new one is amount of pins at he bottom of the hot shoe.
While FT16 has just a single pin the XT32 has 5 of them. It allows transmitter for much more sophisticated communication with the camera through its hot shoe. The key benefit of this better communication is that XT32 supports High Speed Sync and offers flash synchronisation even for maximum of 1/8000sec speed my camera offers. The way to mount the XT32 is exactly the same as the FT-16. We need to plug the USB receiver to the AR400 USB slot and mount the transmitter to the camera hot shoe. In result with the XT32 I was able to shoot with the flash with speeds exceeding 1/300sec without getting curtains visible in the frame. But to shot in HSS mode we need to activate this mode in the AR400 ring flash light first.
We can do this by pressing MODE and Led Light buttons together.
When active we get the H mark visible on the flash screen. Now the flash is synchronised with all cameras shutter speeds up to 1/8000 of the second. Unfortunatelly High Speed Sync has cons I didn't aware of.
I have learnt very fast that after a few high-speed flashes the flash activates the overheating protection function and the recycle time between next flashes becomes 10 seconds longer. In practice it looks like if we set the turntable to trigger the flash every 5 seconds, after the series of flashes we get the flash being triggered every second image. Of course the overheating protection depends on the flash power, but in practice in this mode we can't take images very often. So if we plan use HSS mode to support faster shutter speed, we should set the turntable to take the image at least every 10 seconds. In practice when dealing with standard props, I usually turn the High Speed Sync mode off, set the flash to 1/4 of power, set my cameras shutter speed to 1/250 of the second, set a delay for the turntable between shots to something between 2 to 4 seconds and proceed with the capture and it works fine for me. To summarise, this is the full photogrammetry setup for 3D prop capture I use. T-Shape portable backdrop stand, 2 by 2 meters polyester piece of fabric, a Sirui monopod with triple leg, Syrp Genie Mini 2 rotation device with cables, set of handlers covered with fabric, a micro photography gripper, strong Ball Head to hold ring flash and the camera, mobile device to control Genie Mini 2 rotation, aluminium tripod, AR400 ring flash light with Ring Flash Polariser, lens polariser, wireless flash transmitter and receiver a camera with zoom lens and the X-Rite color checker. This in an optional setup which used to work fine for most generic props I scanned. It doesn't mean its a final one as I learn something new every time I scan something. Of course I would use a a macro lens for very small objects and consider surface coating and markers for shinny surfaces, but the base and rules stays the same. I know there is a field for improvements. Holders would benefit if I use a 3D printer to print them. Also light absorption would be better if I use even better background material or darker paint to paint holders. But this is definitely a very solid starter pack.
It doesn't take much time and space to setup this equipment. I usually start with the backdrop stand and attach the back fabric to it. Next I set the monopod and assemble the Syrp Genie Mini and Syrp turntable together. The Genie Mini device needs to be mounted between the turntable plate and the bottom platform. Next it has to be attached to the monopod. Of course, the choice of holders depends on the type of prop I am going to scan. We just need to make sure that each prop we scan is position in the turntables rotation center, so it's easier to frame and keep in focal range when rotating. The next thing is the camera mount. First I need to set the tripod, attach the ball head. And mount the AR400 ring flash light to it. With the use of quick lock plates its very quick and easy. Next I mount the magnetic polariser on an flash light if it wasn't already mounted. Magnets makes it really easy. I keep the handle up as the handle mark the
maximum polarisation angle when aligned with the marker from the polarisation filter on lens. Next I attach the polarisation filter to the camera lens if it wasn't already attached and I attach the camera to the ring flash. Next I mount the wireless flash transmitter to the cameras hot shoe. Of course the transmitter needs to be set to the same group and channel as the receiver, otherwise they won't communicate with each other. Next I mount the receiver to the AR400 ring flash light. The next thing left before the setup is fully assembled is to connect the turntable to the camera with the cable. First I connect the original Genie Mini 2 Turntable cable to the 1C canon one so it can fit to the camera I use. When done I plug one end of the cable to the Genie Mini 2 camera port and the other end to the remote trigger port of the camera. And that's it. This is the full scanning setup. Now lets turn everything on. First lets turn the Genie Mini 2 ON and connect it with the Syrp app. In this setup, this is the turntable which drives the entire scanning. When connected the app gives us set of control options for the device. For the turntable I pick the one surprisingly called a TURNTABLE. This one allows us to remotely rotate the turntable platform in a direction we push the wheel on a screen. But what is more important, in this mode we can set the amount of photos we want to capture during full 360 degree revolution and the delay between each. When done we hit the REC button, and the Genie 2 starts the capture process. For 36 images it basically rotates the table 10 degrees. Stops and sends the signal to the camera through the cable to take the picture and waits the amount of time we set as delay to turn the turntable another 10 degrees. The camera activates the flash using hot shoe transmitter and takes the photo. The process repeats until full 360 range is covered. When done I manually change the props angle to have it scanned from every side and I restart the full 360 capture pass through the app. This is the result of this approach and image coverage. The entire potato capture with this setup took me around 5 minutes, and basically all I did was to rotate the potato on side and hit the REC button 4 times. But since we didn't finish, lets come back to the actual setup.
With the turntable active we still have to setup the camera and the flash light.
First lets get the camera to the better position so we can frame the prop properly. Next lets turn the camera on and frame the subject.
Set the focal point on the gargoyle we are happy with. I highly recommend to switch the camera to full manual mode with the autofocus and image stabilisation turned off. Turn the transmitter and the ring flash on. Set the flash output power we need, I would suggest to start from 1/4 which is quarter. Of course we need to rotate the polarisation filter mounted on our lens, to make sure its aligned with the flash polariser and cuts all glares from the subject. Next lets set the shutter speed, the shutter speed we set should be at least as fast that the image captured without the flash appears black. This way we are sure we don't capture any surrounding light as the flash light should be the only light source we have. Depending on how bright is the environment we are shooting in, the shutter speed might differ, but I would say that around 1/200 of a second should be fine. Aperture, ISO and take a few test images to make sure our subject is in focus but also to make sure the images aren't under or overexposed. I made a set of small, simple paper checkers which I found very helpful when testing the depth of field. Bare in mind that we can always move the camera and change the distance to the prop as well as adjust the focal length until we are happy with the result. And I believe that's it. This is my equipment I use for 3D prop scanning. Scanned props can be very useful in many areas of 3D. They can be used as reference, or 3D objects for realistic visualisations. But they can be also used to enhance, change or even generate from scratch fully functional PBR materials. They can be scattered and composed as 3D objects in 3D app by hand or scattered using physical simulation systems, but scans can be scattered even procedurally using atlas texture sets which can be generated very easily from 3D data. This way we can easily cover scanned grass material with apples so it can be used next to the apple tree, but we can also scatter the soil lumps to generate totally brand new soil material from scratch. But I guess its a topic for another video. I really hope you found this video useful. If you like this video, and want me to create and share even more content like this one, please hit the thumbs up, drop a comment and subscribe to my channel.
Big thanks to all of you who did it already.
Thanks for watching and hopefully see you next time. Bye :)
such a helpful video!
Love it
Tiny tip: Don't use scotch/transparent tape. Electrical tape works best in my experience.