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

Started Sep 18, 2022 | Questions thread
alfn Regular Member • Posts: 479

PhotoTeach2 wrote:

Great Bustard wrote:

PhotoTeach2 wrote:

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


You mean something like:

You may suggest, but your suggestion would have no photographic relevance. In fact, the 1/3 stop difference in light gathering and DOF between f/1.8 in front of the 1" sensor and f/3.5 in front of the APS-C sensor is, for lack a better word, trivial. Basically any other difference between the cameras *dwarfs* the difference in aperture.

Or did you mean something like:

So I suggest the most practical answer is that the f/1.8 has a (near) 2-stop advantage over f/3.5.

Which is closer to the the "BINGO!"?

The point is that I do NOT CARE about NOISE (until it becomes noticeably objectionable).

And I do NOT CARE about DOF because there are both advantages and disadvantages to both shallow and deep DOF. But overall I prefer deeper DOF because I can create shallow-DOF when needed, (selectively and controllably.

At f/1.8 I can use either a lower-ISO (for less noise if that is a factor).


I can use 2-stops faster shutter-speed, (which may often be very critical).

I BINGO that too-many here are obsessed w/ noise and (shallow) DOF. I support the ability to shoot at higher-SS @ lowest ISO, (for greater DR).


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