Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions thread
OP texinwien Veteran Member • Posts: 3,326
Re: Exposure basics, lesson two point one (& ISO)

Thanks for your considered words. Before I offer my response, I need to request additional clarification on the question of exposure settings.

Jack Hogan wrote:

texinwien wrote: Could you clarify a couple of points for me?

Jack Hogan wrote: It appears that if one wanted to capture the very same tonal range from a scene with the EM5 and the G3, same exposure and all, one would have to set the EM5 at in-camera ISO 3200 while the G3 at in-camera ISO 1600, with roughly similar resulting SNR (EM5 slightly better as per DxO).

How is exposure set in the first scenario - that is, on what basis and by what method? Can we simply, for sake of argument, say that both the shutter speed and the f-number are manually set to be equal on both cameras based on what the G3's meter suggests, when the G3 is set to ISO 1600?

If you'd like to recommend another method for setting the exposure parameters, please feel free to do that. I would simply like to nail them down so there are no further open questions going forward.

I'm following your example, so far.

On the other hand, if one set both at 3200 maintaining the same exposure they would no longer be directly comparable, but the G3 would appear noisier to a naive observer.

Would it appear noisier, and would the observer be naive to believe what he saw?

He wouldn't be naive to believe that he saw more noise (he would). He would be naive in thinking that to capture the same tonal range (shadows and highlights) of the same scene with the same lens and Exposure (ss and f/n) as his friend's EM5 he would have to use the same ISO in the G3. His naivete would cost him a ton of IQ: one stop of highlight headroom and 1 stop of SNR, and he possibly would lose his National Geographic desk

On the other hand an intermediate photographer who understands this subject, would know that to capture the specified tonal range at the given ss and f/n with a G3 he would need to set his camera on ISO 1600 independently of what others need to do to capture the exact same scene and tonal range subject to the exact same artistic constraints. Given the same objectives, his friend with the EM5 and the same lens would need ISO 3200 at the same exposure.

What effect does bobn2's statement that "the bigger exposure will win" have in scenario #2, or does it have any effect at all?

It doesn't apply, because exposure stays the same in every scenario here, only ISO changes.



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