ISO Invariance

[HDNitehawk]

I have yet to come across noise being removed, unless you mean that it is minimized in modern cameras compared to before or minimized with something like faster shutterspeeds. But for the same camera, I see noise as being inherent to different processes. Now are there times when adding upstream noise by adjusting ISO better than adding noise downstream. Yes. Absolutely. That is much of the point of what astro photographers are doing and summarized in this article:

I came across a white paper from Canon that talked about the structure of the sensor. Every step in the process is designed with decreasing noise in mind. For the theory that there is no penalty the ISO Settings in camera must = the EV bar in LR.

This is a comment in your linked article:
"Upon comparison of the exposures, it’s immediately apparent that the Canon EOS 700D/T5i is not completely ISO-invariant"

This would lead me to believe that there are process in the camera that take place that are not completely replicated in LR.

Another article I was reading said that most Canon bodies are not all invariant.

This sounds like a rehash of the Sony DR argument / debate.

[HDNitehawk]

Start on page 17

http://www.robgalbraith.com/images/c...hite_paper.pdf

[Kayaker72]

I came across a white paper from Canon that talked about the structure of the sensor. Every step in the process is designed with decreasing noise in mind. For the theory that there is no penalty the ISO Settings in camera must = the EV bar in LR.

This is a comment in your linked article:
"Upon comparison of the exposures, it’s immediately apparent that the Canon EOS 700D/T5i is not completely ISO-invariant"

This would lead me to believe that there are process in the camera that take place that are not completely replicated in LR.

Another article I was reading said that most Canon bodies are not all invariant.

This sounds like a rehash of the Sony DR argument / debate.

Thanks for the article, that was a great level of detail at the pixel level.

As for the Sony DR rehash...maybe. I never had an issue when people were talking about how good Sony sensors are/were. The numbers are there and there is a reason why so many other companies (Nikon, Apple, etc, even Canon for 1" sensors) buy Sony sensors. The issue I often had with the Sony DR debate was the sentiment that Canon sensors were somehow awful and that everything else that Canon did well was insignificant. Also, there was a tendency to give Sony a free pass on everything else (AF, lens lineup, weather sealing, battery life, etc) just because they had sensors that were marginally better. To me, it was a discussion about needles while missing the forest type of debate.

Now, Canon has mostly caught up with Sony with sensors but only certain cameras like the 5DIV, 1DX II, etc (not the T5i).

But, if you want to characterize "iso-invariance" as a discussion regarding the evolution of sensors, by Sony and Canon, and the characteristics of those new sensors, then, yeah, there is some overlap. Lower noise, more DR, etc. One of the things that comes from that is a degree of iso invariance. Whether it is useful or not to your photography is really up to you. But, it is a characteristic of certain cameras over a wide range of ISOs or of most cameras in a selected range.

If you want, you can check out dpreview's comparison tool designed to do just that:
https://www.dpreview.com/reviews/canon-eos-5d-mark-iv/11

If you want a real world application. Here is the baseline of a shot I posted about a year ago where I exposed for the sky to try to get the sun as a fairly tight circle right before sunset:

This includes a 3 stop grad ND filter on the sky trying to get the overall exposure up.

But, in post I bumped up the exposure by 3.1 EV and 62 of shadows which seems to have lifted the shadows by ~4.5 stops overall. This is the picture I posted:

6S0A7685-3 by kayaker72, on Flickr

I do not do this often (and actually had I not been pressed for time here, I would have tried to bracket this shot), but it does have its uses.

But, overall, I think iso invariance is what explains why there are videos by Tony Northup/Fstoppers out there shocked that you can underexpose an image and lift it in post by ~5 stops and have it be about equal to something shot with 5 stop higher ISO. I was actually about to reply, but realized my concept of ISO was perhaps off. Through this thread (comments and research) I've confirmed that ISO is in camera analog gain (maybe some in camera digital gain). The iso-invariance comes into play as camera manufacturers are doing a better job controlling "downstream" noise. As that is better controlled, digital gain in post is getting closer to analog gain applied in camera. Of course, this is going to vary from camera to camera.