To stack or not to stack

John K wrote:

gardenersassistant wrote:

John K wrote:

Using a lower magnification means more depth of field.

I would like to know the context you are thinking of here. It seems to me that, as stated here, unqualified, as a universal statement of fact, that statement is demonstrably false.

Nope, it's true. If I use a FF sensor at F11 and an APC-C sensor at F11 and I keep the magnification the same at 1:1 then both of the resulting images will be macro images -life size.

Yes.

The subject in the APS-C shot will look larger, but only because it's cropped (and it's not different than cropping a FF image in post) and not because of any difference in magnification. It doesn't matter what sensor I use in the example above, the explanation holds true.

Yes.

But neither of these true statements mentions depth of field and therefore neither can be used to substantiate your assertion that "Using a lower magnification means more depth of field", to which your "Nope, it's true" refers.

In contrast, I have provided counter-examples which demonstrate that your assertion is not universally true.

I've seen a lot of twisted "tests" to demonstrate that there is some form of physics defying magic in smaller than full frame sensors. Every single one of them is rigged though...

Is the implication here that my tests are twisted, trying to demonstrate some physics-defying magic and rigged? If so, in what way?

In the current example the much higher magnification produced much larger depth of field.

Not even remotely possible if the aperture stayed the same...

The aperture was different, as clearly stated!

(Strictly speaking I suppose the f-number was stated to be different, and the equivalent effective aperture was stated to be different, but the aperture would have been different too. In any case from what you have written above I think you equating f-number and aperture, in which usage the aperture was clearly stated as being different.)

You made the following unqualified assertion (e.g. without regard to whether apertures are the same or different): "Using a lower magnification means more depth of field."

I gave two examples of situations in which that assertion was false. For the avoidance of doubt I will repeat them.

In the current example the magnification of the FF image was 12:1. The magnification of the 1/2.3" image was 2:1. 2:1 is a smaller magnification than 12:1. The depth of field was smaller in the 1/2.3" image. Therefore, the lower magnification was associated with the smaller depth of field. The contradicts your unqualified assertion that "Using a lower magnification means more depth of field."

You have tried to disprove my assertion that "the much higher magnification produced much larger depth of field" by saying (correctly) that this cannot be the case if the apertures were the same. However, the apertures were not the same and so this correct statement has no bearing on my assertion that "the much higher magnification produced much larger depth of field".

Perhaps a graphic would help at this point.

My previous example showed pairs of images of the same scene captured with cameras with different sensor sizes. The magnifications were therefore different. The depths of field were the same. So in those cases lower magnification gave the same depth of field. This contradicts your unqualified assertion that "Using a lower magnification means more depth of field."

You have not said anything about the previous examples, except a response of "Thanks (nt)" to the post containing them, which does not prove that my assertion that " lower magnification gave the same depth of field" is false.

You're trying to prove that the sky is green...

You are demonstrating the falsity of things that I have not said and things I do not believe.

Depth of field is strictly a function of magnification and aperture.

Yes.

If you're seeing a difference in your tests

That depends on what difference you are referring to.

If you are referring to my seeing something different from depth of field being strictly a function of magnification and aperture then I'm not.

On the other hand if you are referring to my saying that the FF image had greater depth of field than the 1/2.3" image of the same scene, or that an image captured with a larger sensor had greater depth of field than an image of the same scene captured with a smaller sensor then that is a difference I am seeing, and one that presumably everyone else can see too.

Here is (once again) the difference that I am seeing.

then your testing methods are flawed...