Requesting to delete the ISO is a stupid request because it gives an indication of how much gain was applied to the raw data to achieve the desired image lightness especially if the image is a sooc jpeg.
I set exposure* without considering iso at all as long as important highlights are not clipped.
My final image lightness is set in post, not in camera.
* exposure. - amount of light that struck the sensor per unit area while the shutter was open.
...and another one!
Not sure what "the iso field" is, Donald, please clarify.
Are you talking about deleting EXIF tag #0x8827 or setting it to zero or what??
I would go further and delete the ISO knob from cameras, leaving all photographers. with - guess what - aperture and speed to play with.
Where does it teaches that it is the same exposure? It teaches that if you change ISO setting you have to change SS or f stop.
The problem is that the triangle by itself teaches nothing. It is a diagram. However, you'll find that the vast majority of sites that use the triangle do indeed teach what Danno suggests, and the triangle itself re-enforces that. It is called 'the exposure triangle' and the sides are labelled 'shutter', aperture and ISO. The natural inference is that those together make up 'exposure' and very few if any teaching (word used advisedly) materials that use the triangle say anything to counter that false notion.
To what end?
Can one change "ISO" in raw conversion?
That's a way of saying "you all are right, you are communicating science, and those who disagree with you are wrong". Not your intent, right?
But you don't have to do that.
And that one doesn't need to do that was systematically taught for 80+ years by, say, Adams, who was not a scientist but a practitioner.
If you shoot stationary subject at 1/50 sec f/5.6 and than want to shoot a bird in flight at 1/2000 sec f/5.6 with in the same light, you do not have to change ISO on the camera?
That's about a 5-stop range. Say the ISO was at one of the high conversion gain ISO numbers for the first shot. Then you could shoot the second one at the same ISO and give it a 5-stop push in post. You'd have the same amount of shadow noise and better highlight control. I don't recommend planning for 5-stop pushes because of profile twist and MILC EVF dimness. But you could do it, and it would likely work just fine.
All of the above only applies to raw shooting.
Here's a tutorial:
www.lensrentals.com/blog/2023/05/how-digital-cameras-determine-exposure-part-1/
www.lensrentals.com/blog/2023/05/how-to-expose-raw-files-part-2/
I don't remember Sigma/Foveon telling you can't do that. Those cameras don't change ISO for capture, only for raw conversion.
If I am shooting 1/50 f/5.6 at ISO 100 for the lighting conditions. If I will shoot at 1/2000 f/5.6 in the same lighting conditions at ISO 100, I will get a pitch black image or close to it. So I will have to increase ISO in order at least to see what I captured.
I think that the problem here is the thinking behind the words 'have to'. ISO is a guide to setting exposure. The photographer has freedom of decision both with respect to the exposure controls and the processing decisions. You don't 'have to' follow the guide. You might choose to do something. If you're making a choice, it's best to know what's underlying that choice.
You have added a condition: you picked a low-conversion gain ISO -- at least it's a low-conversion gain ISO on any camera I know. Let's make the first exposure at ISO 640. Let's assume the EVF image is not too dark for you to frame the second picture. The raw file should be developed with a bit over a five stop push. Then it won't look too dark. I just picked up an X2D and set the exposure for 5 stops under ETTR. The finder image wasn't pitch black. The camera's AF worked properly. I could frame the image in the EVF.
As I said, I don't recommend planning for 5-stop pushes, but they're not the worst thing in the world.
If the scene is pitch black, you will have no image.
Otherwise, the image is as black or as light as you display it.
Either you changing ISO in camera or pushing in PP, you still changing it to achieve desired lightness.
