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

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Well done Alyn! I'm glad you did this video so I didn't have to 😜 You did a very nice job of explaining the major concepts in plain language and how they relate to astrophotography. I think your lead-up explanation of exposure stops and then the visual difference between ISO100 pushed 5 stops vs. ISO3200 at 04:51 is especially effective, and will hopefully get more people thinking about this in the correct way, and not just insisting to me that it's as simple as: higher ISO = higher noise. Also, that's an epic filming location for your talking head stuff!

Good video, I just have two comments on it: 1. You mention that higher ISO means lower dynamic range. While true, it's important to realize that simulating higher ISO by underexposing and correcting in postproces does exactly the same. When you underexpose by e.g. 3 EV, it means that you only use 1/8 of the available range, i.e. lose 3 bits (or 3 EV) of dynamic range. And when you check the graphs of dynamic range by ISO, in the intervals of ISO invariance you can see exactly 1 bit (or 1 EV) of loss for each ISO step. Which is not really a surprise, considering that in these intervals you essentially just choose if it's camera processing chips or your software in PC who does the multiplication or division, the values produced by the sensor are the same. In other words, dynamic range is not really an argument for underexposing and correcting in postprocess, the only reason to do that is to prevent clipping. 2. People often tend to think that an ISO invariant camera automatically means it's better. This is not always true, all it means is that the sensor has only one actual gain value and every other ISO setting is simulated by multiplying or dividing the values from the sensor by a constant - i.e. exactly what the exposure correction in postprocess does. While more convenient, it does not always mean a multi-gain sensor could not achieve better results (in the sense of less noisy image) for a particular combination of exposure settings. Often the reason for using a multi-gain sensor is to get better results in some parts of the range, it would be easier and cheaper to use just one gain and simulate everything else by recalculating in firmware.

I realized that my whole photography life was a lie after watching that video...yeah that makes sense Alyn. Great presentation! :)

Fantastic video as always Alyn and thank you so much for recommending my video :)

17:40 - Sony a7iii has a function called "Bright Monitoring" that enables you to see in the dark before the shooting without changing the ISO. Just assign a custon button. Thank you for the video!

This was so useful Alyn. I've struggled with articles about ISO invariance but you make it so very clear and understandable. Thank you so much.

Finally!.. This is the first video/article I've found which explains it to my satisfaction, as a photographer (and as a Sony shooter). Seems like most people seem to get bogged down in more of the technical aspects of it all, causing me to involuntarily tune out. You spoke to us as a photographer, rather than an engineer, and I followed you from beginning to end. Thank you.

This video is PURE GOLD!!! Thanks Alyn, much appreciated

Finally, a clear and complete explanation about ISO invariance. I’ve got a Sony a7III and I’m gonna do it from now on. Thank you very much, Alyn!😊😉

I feel like i should pay you for this lesson haha. Top stuff mate!

Thank you so much Alyn! Your repetition is perfect for teaching new concepts. I learned so much from this video - even what a full stop is pertaining to ISO.

This is turning my head upside down on my go-to astro camera settings, incredibly useful info! Looking forward to trying this out.

Thanks for another really informative & useful video. “Protect the highlights & increase the dynamic range will be my new mantra”!

Good explanation, in fact the best I've seen. As I use a Fuji XT-2 I've come to set the ISO at 1600 for everything and adjust in post with the exposure module (Darktable). Works great. I'm pretty sure that Sony developed this technology and Fuji uses the Sony sensors (although they don't like to admit it). One additional point - while the noise stays the same the dynamic range does not. As you increase exposure (in post) the dynamic range decreases. (You covered this later in the video!).

Thanks Alyn for this detailed Video, this gives me a better understanding of my A7 III while out in the field for NightSky photography. Great content as usual !!

Thank you very much. I think this was one of the most important videos I watched the last years. A7iii.

very informative Alyn, never looked at my camera performance in this way so will definitely try it out

Wow, that's super useful. I'm buying my first dslr in march and these tip videos will most likely be very useful for me. Keep up the good work Alyn

Your awesome alyn I have learned more from you than i have from 3 years of my own experience I'm happy there are people like you that would like to share their information instead of hiding it Thank you alyn Thank you

I'm gonna have to watch this again with a strong coffee. Amazed that high ISO does not equal higher noise!

Well shit, I have some homework to do this weekend. I knew about this issue but I tend to go to iso 100 every time and now it seems that may not be ideal. Thanks for this Alyn!

Wow this was so eye opening and informative thank you so much Alyn !

Excellent video Alyn, and the best one I've seen in the topic.

Close to 80K subscribers Alyn :) An interesting vide once again, thank you.

Excellent work and thorough description on the ISO-invariance topic. Excellent info.

I couldn't agree more. It is exactly how I choose my iso. I just add that I reduce the iso if I am doing a single shot or stack images. If it is a panorama I reduce too but keep an iso where I still can see the composition in each shot.

Thanks for all the work you put into making the videos

I've been trying to get my head around ISO invariance for months but couldn't grasp it. That was until I just saw this video which explains it perfectly. Thank you. i also own an A7iii (bought after watching many of your videos). It's nice to know I have the tools, if not yet the skills, to attempt astro photos like yours.

A great explanation Alyn now I’ll just have to test my Fujifilm. Thanks for a very educational vlog dude. 👍🙏

Great video Al!

First time I've heard of this. You explained it very well and easy to digest. Thanks for sharing.

Many thanks for this Alyn - I've learnt something new today! And the best news for me - my camera is an XT-1 😁. So I never need to worry about ISO ever again - Auto ISO for me from now on 🥳🎉

Great video Alyn, this will give me something to work on in the next few evenings..

Wow! This is incredibly useful information. I've gone all this time assuming ISO100 was always best when possible. I am eager to do this test with my camera and learn at what point it truly performs best.

Alyn this video is pure gold 🤯 💪

Excellent video Alex. Had the Fuji XT1 which I used for a few Milky Way shots. Was always impressed with its noise performance, especially when boosting exposure in post.

Very well done on a complex subject. Loving my D750!

thank you so much, this is perfect timing as I just changed camera

Nora by Space Light! that explains a lot and even simple enough for Noggin here to understand! Thanks so much Alyn - certainly wasn't aware of this and very much appreciated!

This is very good. I knew very well before watching the video what ISO invariance is, but I still believe this might just be the best explanation of the topic.🙏🏼 Thank you.

SO so so helpful! Explains some issues I was having. Made notes! Thanks! 😁

Brilliantly explained Alyn ! Looks like my old D750 is coming out of retirement for my astro shoots !! Diolch !

That was a fun little experiment! I was not expecting the drastic color cast at the lower ISOs though. Proved very helpful in understanding the capabilities of my camera better. Thanks.

Great Video as Always! Very informative! In your video you mentioned you could raise your iso to it's highest setting to compose then lower it back down to the minimum invariant iso.. what I do on all my Sony cameras is turn off the live view setting effect.. to compose.. then turn it back on for the shot.. I have setting effect on/off as a toggle on one of the programmable buttons. If you know your manual settings are correct and you are going to shoot all low light.. you can leave live view setting effect off the whole time. Works for me.. your mileage may vary.. lol.

That's something no one talks about.. thanks man 💫👍

Brilliant! A real eye opener. I'm subscribing. Thanks!

Cheers Alyn, as an A7iii user that was great for me, very well explained.

If that hadn't been so well explained, it could have been a very difficult topic to grasp. Amazing job dude.

Alyn, This is an excellent video and introduced me to something I was completely unaware of. I'm just starting out with Milky Way photography (I love it) and was under the impression for shooting foregrounds/dark parts of my image to shoot a longer exposure at lower ISO to try to keep the noise down, but I wasn't having success at all and my low ISO images were very noisy. This completely explains what is going on and that I should not be afraid to shoot much higher ISO to capture information in the shadows. I'm shooting with a Canon R5 and ran this test myself and found that between ISO 800 and 6400 my camera is ISO invariant which is a huge bit of knowledge for me and should greatly improve my images.

My second rime around with this video. Great explanation! I get it now!

Oh man! I just bought a Fuji X-T1. I've heard of ISO invariance in the past but never thought I'd get to play with one! That's awesome! Great video! Cheers from Costa Rica

Thank you for explaining that concept very clearly ! Will use the 640 ISO on my A7III for astrophotography, low light scenes and day to night time-lapse from now. Nice to know there's always a way to improve our skills and image quality 😉

Thanks Alyn - wish I'd watched this a couple of days ago!

Thanks for the deep dive into this topic.

Brilliant.... Learnt something new and so clear, going to test my Canon 600D now to get the best ISO for my astrophotos. Great tutorial 👍

That was insanely useful. Thank you for the detailed explonation

Great tip Alyn, thank you

Very useful video Alyn. Thanks for the efforts 🙏

It DID make sense! Very conclusiv explanation - even for the German listener. Thank you very much, Alyn!

First, a direct greeting from Brazil. Your video is excellent, very well explained and didactic. Congratulations on the beautiful work.

Yeah that makes sense! You explained so well. Thank you, thank you, thank you for this lesson of gold!!

Very helpful man thanks for your time and effort

Thanks Alyn. Super explanation and very helpful!

Alyn, thanks for the time explaining, I watched many others, you only one for me that make this clear, I thought was a myth, great job!

You made perfect sense but my mind is blown. Testing my cameras tomorrow fro Invariance. Thanks Alyn

Great video Alyn... Well done

I learned something today. Thanks Alyn.

Great educational video, thanks for putting this together

Total noob here! Thanks, I've never come across this topic regarding ISO before. All I have interpreted prior was the higher the ISO, the more noise introduced. Always keep it as low as possible. Thanks to you, not only do I realize that is not the case, I also know how to figure out what is likely to suit my camera best. Super job of conveying a complex perspective so I could understand. Worthy of a 3rd "Thanks!" for this video.

EXCELLENT Work Alyn ! . . . Thanks

Thankyou Mr. Wallace.

Great video, well presented

Mind-blowing video 😁 gonna make some tests, thanks Alyn!)

This explanation is awesome. Thank you a lot!

Awesome video! Clearly explained!

U explain it very well..thanks for uploading

Your videos are always interesting, even if I can't use your explanations for making astrophotography, it is interesting and fun to watch them because it makes me understand the process and the nature of a made photo as opposed to seeing it in real yourself. I have some experience with other photos though. ❤👍🏻

A brilliant explanation man thank you very much!

Thanks for sharing this. You made it very easy to understand,

Thank you! Perfect explanation 👍🏼

Great explanation. As a software developer who worked with computational photography, iso invariance is a very hard problem to solve. Ideally a short timelapse helps solve the iso issues. Sadly you do get star trailing if done incorrectly.

Excellent vlog! 👌👍💪 Goes well with the one by Tony Northrup where he demonstrated that noise is due to lack of light (wrong aperture/shutter speed) not a high ISO setting.

Indeed!..thankyou so much for subjecting yourself to so many non variants of iso invariance and even variations of iso variance.. ;)

Thank you thank you thank you Alyn!! I should have listen and watched you r earlier. Thank you very much.

Very, very good , extremely well explained.

Thank you for this excellent explanation!!

Well done Alyn!!

Great Video Alyn, nice and clear thanks. I notice this with my Canon 6D mk1 and Sony A7s mk1. This will definitely help with tweeking settings when out in the field with both cameras in the future. 😉✨🌌

Thanks Alyn. I've been tempted to switch back to Canon from my Sony A7 and this has given me second thought. Maybe I'll have both for a while and do some experiments :D

Great video thanks. I was aware of the ISO invariance of my D850 but this is a great practical example of what that actually means in real life!

Another excellent discussion. Something no one else discuses. But in the end you still have to make compromises,

Thanks a lot, I just spend the night on Hearth Nebulea, at 3200, but I just figured out that my best ISO is 800 ! Need to take it again !

Good job explaining this complicated topic! As a long time user of the Fuji X-T1 I can confirm that the camera is pretty much ISO invariant, so much so that I was taking milky way images at iso200 at one point to not blow out the highlights in a campfire. As it turned out, I unfortunately overestimated the performance of the sensor and the darkest regions of the image resolved nearly no detail compared to a ISO1600 exposure. So even with the X-T1 there seems to be a limit of how strong you can underexpose. But in general its still pretty amazing how much freedom you have with the X-T1s raw files.

Looks like I'm going to get busy and shoot some test shots...interesting video, thanks.

Brilliant video. Thank you 👍🏻

That was really helpful! Thanx

Top notch as ever bud 👍 no on ever talks about the d7500 and being a newbee really helps witn settings. Appreciated lots thanks.

Awesome video, cheers dude.

Thanks heaps Alyn.