So a f/1.8 on a 1" sensor would still gather more light than a f/3.5 on an APS-C?

alfn wrote:

Great Bustard wrote:

Bob A L wrote:

Right, it's like

One size does not fit all, when it comes to sensor sizes for photos.

I think that's a given that no one has debated. What was being discussed is how f/1.8 on 1" relates to f/3.5 on APS-C. And the answer is that f/1.8 on 1" projects 1/3 of a stop more light on the sensor as f/3.5 on APS-C for the same scene and exposure time, which results in a very slightly less noisy photo (with very slightly less DOF), assuming similar sensor tech. Thus, f/1.8 on 1" is 1/3 of a stop "faster" than f/3.5 on APS-C, in terms of why we care about the f-number.

However, there may be other important differences between the photos (e.g. resolution, distortion, color, etc.) which matter as much, and likely much more, than the differences in noise and/or DOF, not to mention the elephant in the room, which are the differences in size, weight, price, and operation between the cameras.

So why bang on at such length about the trivial difference in this instance? Why not just say there are many more important factors to consider?

The OP asks a question about the relative performance of two different format cameras used at different f-stops. I believe the question should be answered, correctly? Would you agree or disagree that factually incorrect responses serve to, at best, confuse the matte and, st worst,  to misinform?

The obsession with noise (and so-called total light) that pervades these forums is absurd. One should at least try to keep things in perspective.

While the visibility of noise in a photo may not matter to you, based on the frequency with which it's brought up as an annoyance, as something to mitigate up front or to remove after the fact, it clearly matters to others.