Why do reviewers do cross-format equal-ISO camera comparisons?

Started Aug 30, 2012 | Discussions thread
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Why do reviewers do cross-format equal-ISO camera comparisons?
Aug 30, 2012

Futile though I'm sure it is, I'm going to start off by pleading: no need to go into the math and physics for me. (In microscopy where I come from, if we want to compare two "grandma's faces" we always always start with the same number of photons producing both copies of grandma's face--only then can we begin to conclude things about variables other than photon noise [which is boring and pre-determined by physics] that might account for differences between the quality of the two grandmas).

That "out of the way," I'd like to know whether there's some justification that I'm not aware of for why all camera comparisons on the web (literally all of them, including m4/3 partisans!) compare at the same ISO--given that their stated goal is to compare the differences in camera noise--ie the sensor QE--not the boring photon noise that's determined by physics a priori. It would be so so much easier (for me anyway!) to interpret the results if we started the comparison with an m4/3 grandma that produces the same photon noise as the APSC grandma--then what's left over are camera-specific differences that guide my purchasing decisions.

The only argument I can think of is "simplicity."

But I don't get that. I mean no one compares 4/3 45mm grandma to FF 45mm grandma. And someone decided that that's not too complicated for readers to understand. So why should we assume that it's too complicated to compare 4/3 f/1.8 ISO 800 grandma to FF f/3.6 ISO 3200 grandma?

I don't think it does "us" any favors. For example the conclusion that most people are likely to draw from from all the OM-D comparisons is that m4/3 has "caught up" with APSC--which of course generates the expectation that this must continue in all future cameras! When in fact, of course, the only conclusion to draw is that Olympus has temporarily pulled ahead in sensor QE, (while in the long run when everyone is on the same average sensor quality, m4/3 f/1.8 ISO 800 grandma must physically have the same photon noise as FF f/3.6 ISO 3200 grandma).

It seems to me it does no one any favors (I can barely interpret the images these comparisons show me), but I'm asking specifically to find out whether reviewers have some other reason for continuing comparisons that seem at best difficult to interpret, and at worst fundamentally misleading...

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