ISO & Dynamic range - what is going on?

Thank you, Ian!

Now I can play with the ISO definition of DR ... like Captain Oates, "I may be some time".

Thanks again ... the mysterious 'A74Me', can't imagine who that is, eh?

This is not an issue with the limited DR of either camera, This could be processing, the color space, an exposure to large for the used iso setting, and even heck if this was further processed using Zerene Stacking software so really who knows until you figure this out.
If you are using Zerene what color space are you using I would start off using prophoto 16 tiffs
Are you processing the stacks using Pmax and if so are you using UDR?
Are you using all color channels in decisions when processing ?
Dmap is better at preserving color and highlights over having better detail recovery.
Heck even Zerene adds a lot of contrast that is causing the issue.

There are too many unknowns to derive anything of use from your assertion in the differences between the cameras

did you like that thread 😎every man and his dog was in on the action nearly topped out the thread max. nothing like posting images.

😁my gallery was alwasy a dead givaway. I had 23,000 posts on DPR without 1 ban ,i just posted to many images and told i was belittleing members with them 🤨 that was 5 years ago, not many original members post there much now we have all been put on moderation.

i shot some single RAW doll test images not a fake test image on DPR. i gave the a7r5 back the next day it did not hold up to the marketing hype one bit.
and boy it was slow using a field monitor. i did enjoy having a play with the only A1 mk2 in australia as well at my studio 😊 wouldnt waste my money on the a7r5 id go for the A1ii. but it to was slow with a field monitor attached 🤨both my a6700 and a7iv are instant no delay at all.

Dmap better 🤨it cant even stack my complex spiders, please explain what you call better 🤔if you cant post a comparrision for us to see what your stacking.

i think i will use what ive been doing for 8 years. thanks for sharing your experiences.

You should look at using Zerene stacker to its fullest potential, Zerene is not a one trick pony that you use either one or the other, the software was designed around using both at the same time, one for detail and the other for maintaining color and contrast

the image i posted is from both at the same time. its a 1 trick pony

Another way to look at the original post.

In simpler times: ISO=10/Hm where Hm is the exposure. Re-arranging that we get Hm=10/ISO. Which tells us that, as we cranked up the ISO , the exposure went down because the camera adjusted the aperture/shutter combination to match. For example, going from ISO 100 to ISO 200 would lower the aperture/shutter combination by 1 stop.

For any sensor, less exposure means more noise which means less DR, period.

For any sensor, if the DR increases with ISO setting, the camera manufacturer is messing with something and breaking the intent of ISO.

This is where I disagree, and is kinda what I was alluding to in my earlier posts. Digital photography is primarily designed to make "visual sense" and if we keep trying to fit it within our ideals of "numerical sense" then we are in danger of inventing a mathematical model to fit our need rather than understand the truth. ISO is simply the calibration of middle grey in the output jpeg. ISO is not implemented in RAW files in a way that allows you to use it as a constant in equivalency calculations to 2 decimal places. The answer to the original question shows this. I think it's more that photography forums set an expectation of what they want ISO to mean and have sort of mislead themselves...

😊 Digital photography is primarily designed to make "visual sense" love this comment, its why i pull the maths apart with images.

Why would you expect the NR to find highlight detail that was clipped away?

NR only increases practical DR by making deep shadows more aesthetically tolerable.

With G2 having a dark area with about 15 raw value and having an SNR of more than 1, the raw data has a ISO DR of log2(15778/15) = about 10 EV, FWIW.

its not increasing DR as demonstrated in the image i posted. i added NR to the raw then pushed up exposure compared to just pushing the original raw.

ISO - the exposure index - is clearly defined by I.S.O. Standard 12232. Nothing said in this thread alters that.

How about we start from scratch
What is DR to you?

What happens when then sensor records data in a tonal value, but in that tonal value all that is recorded is noise can we call that data in that tonal value part of the DR?

If all that data collected by the sensor in a tonal value is nothing but noise, can we say that data is contributing the DR the camera recorded?

If that noise is not contributing to the data creating a image can we not say those tonal values falls outside of what the recorded DR of the camera?

If the noise is the limiting threshold to the tonal range that a camera can record, is it not safe to say that noise is the limit to deepest shadows that a camera can record?

I am reminded of the 'dynamic range of a orchestra' (about 90 dB) where the lower limit was audibility of any kind, musical or not. In other words "noise" was included in the range, not separated out like ISO does. In that case, donning earmuffs would reduce the DR ... 😉