Hello my friends! in this free episode from
photogrammetry course we'll have a look at the camera settings, which are optimal for capturing
photo scans. we'll explore such basic things as iso, shutter speed and f-stop in the context
of photogrammetry, but actually we will start off with talking about raws. as we have
mentioned already, such important decisions as color management shouldn't be left to camera to
decide. the random in-camera color presets usually just mangle the contrast levels and the colors
in general and when it's coupled with compression of a jpeg format for example, it's a disaster. by
shooting in row we get the access to the sensor data and we can arrange the colors in a physically
plausible way, which is very close to the reference. (more about that in the color management video).
so that's the first thing, switch the raw on. okay let's skip setting the mode to manual for a
minute and talk about setting the white balance instead. an awesome benefit in shooting in raw
is that we don't need to calibrate white balance on set, we can do it in post, on developing the
raw sources, but you would need some kind of a reference, a gray card for example, otherwise
the process becomes a little bit eyebally. in other words we don't have to care about
setting the white balance in camera that much, it all can be sorted out later. the next thing that
we should take care of right away is setting the mode to manual. now every camera has the auto
mode, but it's no good to let the camera decide what the exposure should look like. it will
lead to inconsistent flickering output and not only brightness will flicker but also the
depth of field due to the changes in f-stop. it is much safer to set the mode to manual, that
will fix the iso f-stop and shutter speed settings. alright so we have switched the camera mode to
manual, now what should we do with the settings that contribute to exposure, how to get to the
correct exposure? every camera has the exposure volume meter and the most straightforward thing
that we can do is to keep that meter around zero. well, the ev values of minus one plus
one are acceptable, but if it's around zero it means that you're just doing it right
most likely and hopefully there will be no overexposed or underexposed parts. what are
the dangers of overexposure and underexposure? when the exposure value is set to the right we
run into the risk of clipping the higher end light values, like on the white bricks here. while this is
not the end of the world and we can still try to bring back those highlights in special software
like DarkTable, it's still pretty bad. and obviously if we underexpose the photo or expose
it to the left we will most likely discover a lot of noise in the darks after bringing it up in post.
or we will lose the darker portions altogether. so watching the ev meter is the good starting point.
it's not always possible to keep it consistently around the zero value though through the entire
photo session. sometimes the lighting conditions in one part of the environment may differ drastically
from the other part of the environment. the wall that is further away from the main source of light
will naturally be way darker than the area that is close to it. so after all, as an exception
to this rule of having the exposure value around zero at all times, you may need to adapt
to the changing lighting conditions in the scene. alternatively you probably have such thing
as exposure bracketing in your camera and you can turn it on. exposure bracketing means that the
camera snaps a bunch of exposures on releasing the shutter, for example -2, 0 and plus 2 and then these
multiple exposures are automatically stitched into a high dynamic range file, for example 32-bit exr
in post. we won't go into such details just yet but photogrammetry software accept high
dynamic range files as inputs. that could be a potent solution to the dynamic range
problem, but for now let's keep it simple. next we have to take a closer look at the iso
f-stop and shutter speed values, these three things are probably the most important to nail
and you will be tweaking them most often as well. by boosting the iso we can amplify the sensitivity
of the sensor at the cost of extra noise and degradation of signal, so the perfect value for iso
is the lowest value available, typically, it's the iso of 100. but it's also the darkest value as well.
what could we do to compensate the light levels? simply put, we can use the slower shutter speed,
for example by slowing down the shutter speed to one tenth of a second, we regain the ev
values necessary to get the correct exposure. so yay! we can just use the slower
shutter speed and there are no drawbacks?.. not really. a really slow shutter speed makes a
handheld shooting produce lots of motion blur due to the handshake and neither the optical or
in body image stabilization could help in such case. what could help though is using a tripod.
so if you have some time to move the tripod in between the shots, it definitely sounds like
the best solution. okay, the next super important camera setting is the f-stop value or aperture.
the problem with opening up the aperture to allow more light in is that the depth of field becomes
shallow and once you start closing the aperture by increasing the f-stop value, everything gets in
focus, but everything gets darker as well. and we also need to compensate it somehow. you guessed
it... by slowing down the shutter speed *again*. alright shutter speed saves the day again. so
you're telling us that we should put the f-stop value as high as we can? we need to put everything
in focus, right? well there is a caveat as usual. let's compare two f-stop values: 6 and 20. you can
tell that with the f-stop value of 6 some parts of the wall still fall out of focus, so let's crank
up the f-stop all the way to 20 and compare the results. now it seems that pretty much everything
is in focus and that's a good thing, the bad thing though is that the phenomenon known as diffraction
comes into play. in other words a photograph grows progressively less sharp as you go from f8 to f11,
from f11 to f, say, 18 and at some point it becomes really bad and blurry. at the f-stop of 6 it
isn't prominent at all, but see what happens at the value of 20, everything got a little bit blurry.
that's diffraction and in many lenses it's kind of unavoidable once you start really closing the
aperture. so to find a sweet spot in setting the f-stop value, feel free to experiment with
the f-stops inbetween, let's say, 8 and 11. now let's summarize this section by naming the
optimal values of iso, f-stop and shutter speed again. when the tripod is available and you're
willing to use it, then feel free to set the iso value at its lowest, the aperture or f-stop should
be somewhere in between 8 and 11 and then set the shutter speed to such value to get to the correct
exposure. these settings are a good starting point. but yet there are different environments
with different lighting conditions. let's have a look at how the camera settings
would change, depending on the environment. let's say we have to photo scan a dim lead place
like a warehouse. the camera settings that we have just discussed are very universal and they're a
good fit for dim lead places as well, first of all we don't have enough light to shoot handheld, so
we assume that we'll be using tripod. so the first thing we'll do is drop iso all the way to 100,
set the f-stop to 11 to make sure everything is in focus and then slow down the shutter speed to 1
15th of a second to get to the exposure value of 0. you'll need a tripod to keep the camera steady
at such shutter speed and you'll probably need to set a timer in the camera settings in order to
not shake the camera additionally on releasing the shutter. or alternatively, a remote would come in
handy in order to not press any buttons at all. many modern cameras can connect to smartphone,
so that can serve as a remote. the other type of photo scanning scenario is when there's enough
light to shoot handheld, for example outdoors. by saying enough, usually it's not nearly enough
to drop the iso all the way to the lowest number, so a compromise have to be taken. for example
iso 200, f-stop 5.6 or something like that and then the crucial thing when shooting handheld,
the shutter should be set as fast as possible, let's say, faster than 1/50 of a second
otherwise it will be shaky no matter the optical image stabilization or in-body
image stabilization. the important thing to understand about shutter speed is that it's
measured in seconds or fractions of a second and at first it could be slightly tricky to
interpret the numbers after the division sign or the slash symbol. the higher is the number
after the division sign, the last time the shutter remains open, so a 50th of a second is actually
two times slower and two times brighter than a hundredth of a second. and obviously one second is
much much slower and brighter than one hundredth. returning to our handheld scanning example,
the shutter speed should be pretty fast to avoid motion blur. it also depends on the
focal length, but let's say without going too deep into the weeds, that the shutter speed
for the handheld shooting should be somewhere in this range. it would be a pretty safe bet even
for the hands that are not super steady like mine. but what camera settings to set in the darkest
dungeons, where there is very little light indeed? in such extreme conditions, enabling the in-camera
flash may come in handy. the iso should be at its lowest, f-stop at 11, a pretty fast shutter speed
and the flash. the flash may lead to lighting inconsistencies in between the shots, but what
can we do. generally it still works well enough in reconstruction. so in camera flash could be a
viable method of scanning such dark environments. a few words about the drive mode now. typically
the drive mode should be kept at single shooting. it's usually set like this by default, so you
don't have to touch anything to activate it, in some cases, when there's plenty of light, the
drive mode can be switched to continuous shooting. by activating this mode you tell the camera
to shoot in bursts, so you press and hold the shutter button and it behaves somewhat like
shooting a video. it's fairly hard to do it like this though, so i would recommend to stick to the
single shooting mode. so these are the essential camera settings used for photogrammetry,
it is important to understand them all, it would take some time and some practice most
importantly to memorize all these settings and use them accordingly, but it's totally worth it to be
able to create the highest possible quality models. in addition to the camera settings that we have
just discussed, it's important to reiterate the lens settings useful for photogrammetry once more.
as we've mentioned before the quality of the final photo scan largely depends on the quality of
pixels in the source photos and that depends on the quality of optics alongside other things.
some lenses tend to produce a lot of chromatic aberration and other artifacts while other lenses
are much much sharper and cleaner in terms of how they render stuff. the prime lenses usually
tend to be slightly better than the zoom lenses in terms of these artifacts, but the zoom lenses
also perform very differently depending on the focal length for example. and not only the focal
length but also the diaphragm value or the f-stop value. it is worth checking on the internet what
are the sharpest focal lengths for your zoom lens, for example 50 millimeters proved to be
sharpest on Sigma 17 to 55 millimeter zoom lens and in addition to that the f-stop value of 8 has
proven to provide a quite sharp rendering as well. so that's definitely something to check
out if you have the variable zoom lens. okay what else can we say
about the zoom lens settings? the photogrammetry software loves when all the
source photos have been captured at the same focal length, that makes it easier to reconstruct,
so if your lens doesn't have a switch that fixes their focal length you can do it manually
by simply taping it. yeah I know it looks gross :) the other factor that influences the choice of
the focal length is framing, how do you like to frame the object. if the object is pretty small and
you still want to frame it in the optimal way so it occupies the most of the image, then zooming in
and going with the larger focal length makes sense. as for the f-stop value, as we remember, the
larger it is the wider is our depth of field, in other words typically it should be around f8
or even f11 for the optimal depth of field and everything in focus. framing wise, we may want to go
slightly wider in the narrow spaces like corridors, it makes sense to go as wide as possible whatever
it is, 24 or 14 or even wider than that. if you use a crop sensor camera then going fisheye is
must-have in some places. so the type of the environment obviously affects the choice of the
focal length and the lenses for that matter. thank you so much for watching and of course if you
have any questions related to photogrammetry and specifically related to camera settings in the
context of capturing photoscans, feel free to leave your comments below! and of course make sure
to check our Complete Photogrammetry Course on Blender Market, Gumroad and on creativeshrimp.com.
and actually check our Discord channel that we are testing at the moment, there is a special
chat for the photogrammetry course students there as well as the support channel for
the course. all right stay safe and see you!
