What's The Best ISO For Astrophotography (ISO Invariance)

take a look at this image here i promise you there's an image there it was taken at f2 one second shutter speed and iso 800 and look what happens when i do plus for exposure value in lightroom boom we now have a stunning picture of the aurora borealis above the norwegian fjords and despite boosting the exposure of a massively underexposed image it's pretty clean there's not much noise there so why is this it's all thanks to something known as iso in variance so in today's video i'm going to explain to you guys what iso invariance is how we can test our cameras to see whether they are iso invariant or iso variant and then from that we can find out what the best iso to use for your camera is in low light conditions then i'm going to explain some use cases where iso invariants is really useful but what i'm not going to do is explain the technicalities of the camera electronic circuitry that enables this behavior because i don't think many of you would be interested in that but if it does interest you i'll put a link to another video in the description down below which i think is one of the best explanations on youtube that's also quite easy to digest and understand but before we get into the nitty-gritty of today's video a quick message from the sponsors nordvpn and if you didn't know what a vpn is it basically encrypts the connection between your computer and the internet which protects your data from hackers from snooping governments and those pesky websites that log your searches and target you with specific ads now i personally will never use a public wi-fi without using a vpn server because you never know how secure that public wi-fi is or whether there's hackers just waiting for people to log in so they can steal their data and steal their information so i will always use a vpn service when i'm using public wi-fi another good news for vpn swimmers is that you can pretend that you're in a different country and unlock content that is geographically specific so for 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surprise so follow the link in the video description down below use my special code to get your free month your special gift and make sure your connection to the internet is secured with lordvpn so what is iso in variance let's pretend we have a perfectly iso invariant camera and we take two images at f 2.8 15 seconds but with different iso so iso 100 and iso 3200 if we take the iso 100 image in post-production and boost the exposure by 5 ev or 5 stops the two images will look pretty much identical they'll have the same amount of noise and it'll be impossible to tell which one was taken at iso 3200 and which one was taken at iso 100. so iso 3200 is five stops brighter than iso 100 a stop is basically when you halve or double the amount of light in an image or the exposure of an image and for iso 100 you double it to get 200 double again to get 400 800 1600 3200 so iso 3200 is five stops brighter than iso 100. so because there's the same amount of noise in the 100 image of the 3200 image we can say that the amount of noise in the image is invariant of the iso setting that you used so boosting or dropping the exposure in post-production is exactly the same as changing the iso in camera in the field so sometimes these cameras are known as iso less cameras now let's do the same with an iso variant camera so two images f 2.8 15 seconds iso 100 and another image at iso 3200 but this time when we boost the exposure of the iso 100 image by five stops we get an image with much more noise a lot more grain and degradation of the image quality so with iso variant cameras we can say that the amount of noise in the image varies depending on the iso setting that you use so with iso variant cameras you have to be careful what iso setting you use in the field because you don't have that freedom to boost or drop the exposure in post-production like you do with iso invariant cameras i hope i haven't lost you yet now i'm not sure who was the first to do this kind of sensor technology but i think sony can be credited at least for bringing it into the mainstream because all of the cameras on the market that exhibit iso invariant behavior are either sony cameras like the sony alpha cameras or cameras from other manufacturers that have sony sensors in them like the nikon d750 and the fujifilm xt1 both very iso and variant cameras both have sony sensors in them but i'm not sure exactly who was the first to do this kind of technology but a lot of the signs point to sony canon dslrs i want to say all of them but i'm not 100 sure so i'll say most of them most canon dslrs are iso variant you really have to use the right iso in camera but it's not as straightforward as a camera being iso variant or iso invariant there's a few different behaviors so we have iso invariant cameras which are quite rare the fujifilm xt1 is a really good example like all of the iso settings are iso invariant the nikon d750 is very close but iso 100 is very noisy from 200 onwards it's also invariant we also have dual gain iso invariant cameras so you have two levels of iso in variants and you may have heard me talk about this with my sony a73 in my past videos so from iso 100 to 500 it's iso invariant all the images look pretty much the same as long as all the other settings are kept the same but then from iso 640 upwards there's another level of iso in variance where all of the images from 640 upwards will pretty much look the same as long as all the other settings are kept the same so there's two levels of iso and variants these are known as dual gain iso cameras and usually the higher iso so from 640 and upwards those isos are better suited to low light conditions they'll have less noise than the lower iso images then of course we have iso variant cameras where the noise varies as you change the iso but at some point most isovariant cameras begin to show iso invariant behavior which all might sound a little bit confusing right now but let's find out whether your camera is iso variant or iso invariant to do this take your camera into a low light scene whether that's a dimly lit room or a nighttime scene with not much light pollution make sure your camera is in manual mode make sure you turn off long exposure noise reduction make sure you turn off high exposure noise reduction and then you want to keep your aperture and shutter speed the same for all the shots so for me at a night time scene with not much light pollution i'd probably do f 2.8 and 15 seconds and then take different exposures at different isos and rather than doing every iso setting on your camera just stick to the full stop so 100 200 400 800 600 3200 and so on once you've done that take your images into lightroom or whichever raw editing software you use and the idea now is to match the total exposure values of the images so to match the exposures in lightroom we're gonna use the exposure slider and because the exposure slider only goes to plus five and minus five we're going to start with the iso 100 image and do plus five exposure on the iso 200 image we're gonna do plus four on the iso 400 image we're going to do plus three and so on and so on until you get to iso 3200 where you can just leave it set to zero and then the iso 6400 is minus one exposure iso 12 800 is minus two exposure but it's a quick and easy way to do this in lightroom so make sure you've got the images in the same folder and then what you want to do is select the iso 3200 image press d to go into develop mode press control and a to select all of the images in the folder or command dna on a mac and then you can go up to settings match total exposures or you can see there's a keyboard shortcut ctrl alt shift and m or command alt shift and m on a mac so i'm pressing that lightroom is automatically going to match the exposure value of all of these images so as you can see all the images are now the same brightness if you wanted to make any adjustments so for example the exposure overall is a bit dark so if i was to lift the shadows and lift the blacks to see what's going on a little bit better i can now sync the settings with all of these images but i'm going to check none and just tick shadows and blacks and now all of the images will have the shadows and the blacks adjusted but the exposures are going to be left so that they're all the same exposure value now we can assess the images and find out whether your camera is iso variant or iso invariant and i'm going to show you three different examples so let's start with the canon 6d which is an iso variant camera so with the canon 6d i took this shot at 50ml f 2.8 8 seconds these are the settings for all of the images but i just changed the iso so this is iso 100 and you can see that it's awful it's full of noise and color degradation but then when we get to iso 200 the noise improves a little bit better so does the color degradation at iso 400 the noise continues to improve again at 800 the noise continues to improve the color degradation also continues to improve 1600 again we see a slight improvement in noise performance 3200 hard to tell but i think just a slight improvement in noise performance less 6400 pretty much the same as the 3200 image 12 800 again pretty much the same and then 25 600 again pretty much the same so the canon 6d is iso variant up until about 3200 and then starts to show iso invariant behavior and i'm sure a lot of you are quite surprised that as i increased the iso the noise performance improved which goes against the misconception in digital photography that increasing the iso increases the amount of noise in your image it's simply not true so if that's news to you and you've learned something in this video already do consider hitting that subscribe button if you haven't already and hit the bell notification as well so you don't miss out on these free useful videos let's take a look at another couple of examples so my camera of choice the sony iii so starting at iso 100 we can see it's quite noisy it's not near as noisy as iso 100 on the canon 6d but it's still pretty noisy and there's a heavy magenta cast on the image iso 200 and we see that magenta cast disappear and a bit of an improvement in nice performance at iso 400 the image looks pretty much identical to the iso 200 image but then when we jump to iso 800 is a slight improvement in noise performance which might be difficult to see on youtube because youtube compresses videos and you lose quality in the video so you're just gonna have to take my word for it and i've obviously tried all of the isos on my sony a7 iii camera and i know that uh between 200 and 500 it's iso and variant and then from 640 upwards it's iso invariant so there's two layers of iso invariant it's a dual gain iso invariant camera so if we continue upwards from 800 to 1600 apart from that red light that appear the image is pretty much exactly the same the noise is the same 3200 again the noise is exactly the same 6400 no changes to the noise performance 12 800 some reason slightly darker but still no real change in the noise performance and then 25600 again no real change in the noise performance and it looks pretty much the same as all of the images that we just looked at from iso 800 so that is a dual game iso camera now let's have a look at the nikon d750 so again starting the lyso 100 the image is pretty noisy similar to the a7 3 maybe and a lot better than the canon 6d but as we jump to 200 there's a slight improvement in noise performance and the colors a little bit better but then iso 400 i messed up the shot um but it's pretty much the same as the iso 200 image and again iso 800 still pretty much the same noise performance 1600 same noise performance 3200 same noise performance and this continues all the way up until 25 600. so apart from iso 100 which is slightly worse than the rest of them the nikon d750 is pretty much iso invariant the amount of noise in the images don't change when you change the iso that's a pretty good iso invariant camera now 100 iso and variant cameras are pretty hard to come by the only one i really know of is the fujifilm xt-1 but i'm sure there's more out there i just haven't researched all of the cameras out there so how can we use these test results to decide what the best iso is for your camera in low light scenes to assess that we need to know a couple of things the first thing is that as you increase iso your camera captures less dynamic range so as you increase the iso you'll capture less dynamic range and the dynamic range is the difference between the darkest areas of the scene and the lightest areas of the scene so as you increase the iso dynamic range decreases the second thing you need to know which is pretty much a consequence of the first thing is that as you increase the iso you increase the risk of blowing out the highlights in your shot which means you lose detail and you lose color in the brighter regions of your shot they become white and there's no way to recover that detail because they are fully blown out so in that sense we want to keep the iso as low as possible so that we can capture the highest dynamic range and so that we can protect the highlights in the scene but as you can see from the noise tests we want to use a high enough iso to get good noise performance so the best iso for your camera will be the lowest iso that gives you the best noise performance in the case of the canon 6d it was iso 3200 because after iso 3200 there was no improvements in the noise performance and if you go any higher than 3200 you're going to capture less dynamic range and you're going to increase the risk of blowing up the highlights in your image for me with my sony a73 the best iso would be iso 640 because after that there's no improvements in noise performance and again we don't want to go higher because we captured less dynamic range we increased the risk of blowing out the highlights however iso 640 is very impractical in the field because your images will pretty much be black for the most part so i still find myself shooting an iso 3200 an iso 6400 so that i can see what i'm doing i can see the photographs that i'm taking in the field but if there's a situation where i need to protect the highlights if the moon is in the frame or the aurora borealis or a street light i can take a shot at 3200 so i can compose my shot and then i'll bring the iso down to 640 which is technically the best iso for my camera in low light situations which will protect the highlights and capture the highest dynamic range with the nikon d750 the best iso would be 200 because 100 was slightly worse than all of the other isos but iso 200 offers you the best noise performance you know if you go any higher you don't get any improvements in noise performance but if you do go higher you decrease the dynamic range that you capture and you increase the chance of blowing up the highlights in your image i sound like a broken record i'm sorry but i hope you understand but again with the nikon d750 iso 200 is just not practical in the field so you'd still want to use 3200 6400 but if you need to protect the highlights you can lower the iso if need be so this is the general idea of iso invariance if your camera is iso invariant you can lower your iso to protect the highlights and capture a higher dynamic range single exposure so when is this useful well i've just talked about a few example cases if the moon is in your frame the aurora borealis or the street light and you want to protect the detail in those highlights you can use a lower iso and then you can bring out detail in the darker regions of the image in post-production and it's especially useful for time lapses of a moon rise or a moonset or the aurora borealis you can use the lower limit of your iso invariants and protect the highlights so this is especially useful with the aurora because sometimes the aurora they just unexpectedly brighten significantly and suddenly and if you're using that lower limit of your iso invariance you're going to protect the highlights from blowing out if you were shooting at 3200 or 6400 because you were exposing for a dark scene and then all of a sudden the aurora just ignites your highlights are going to blow out and the aurora is going to be white and you're going to lose all the detail and color and that happened to me in norway in senior so i'll just show you this example time-lapse now the aurora started off really dim and then all of a sudden it just just illuminated the entire landscape but because i was using iso invariance low iso my highlights were protected and i didn't lose any detail or color if the aurora didn't ignite i can boost the exposure value of the images in post-production and make them bright enough and decent enough to see the detail of the image now an example where you can take advantage of the higher dynamic range you can capture with a lower iso would be in deep space astrophotography so a target like the orion nebula as you saw in my recent vlog when i captured the orion nebula using my sony a7 iii i shot at iso 640 because that allowed me to protect the detail in the bright core of the nebula and that i can brighten the darker regions of the nebula and bring out those dust lanes in post-production without worrying about unveiling extra noise from boosting an underexposed image because the image is iso and variant and you can just boost that brightness in the dark region so this is a really good example of taking advantage of the higher dynamic range that you get at lower iso values lastly another good example is when you're doing a really wide panorama and somewhere in the panorama is a bright town or city and light pollution or even the moon perhaps and you know you if you have a nice variant camera you might struggle to decide whether you want to expose for the darker area of the images and get a good milky way or a good aurora in the sky but then when you get to the town or the city your highlights are going to blow out or do you expose to the town in the city protect the highlights but then the rest of the image will be dark with a nicer invariant camera you don't need to worry about this you can just shoot at the lower limit of iso invariants protect the highlights capture images with a high dynamic range and brighten the darker regions in post production i hope that makes sense if you have any questions please get in the comments down below but i hope that makes sense the general idea of iso and variance is that it allows you to protect the highlights and capture images with a higher dynamic range i think i've said that enough times now already so if you haven't already please hit that subscribe button and if you're going out to enjoy the night sky anytime soon i wish you good luck including skies [Music] you

Channel: Alyn Wallace

Views: 73,241

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Id: d8QV00mkJW4

Length: 23min 16sec (1396 seconds)

Published: Fri Feb 26 2021