Choosing a camera format for Underwater Photography

[Interceptor121]

Provocative not in the literal sense and now you are being offensive which is a bit sad
Anyway if you can't understand DOF equivalence try another source for yourself

 

[Storker]

You really aren't helping your case with that kind of arguments.

 

[Interceptor121]

Your incorrect statement that started your journey

You seem rather fixated on DOF. What if DOF isn't the end-all, be-all, but if decent SNR is more important than optimal DOF?

I am not fixated by depth of field. Depth of field equivalence is a method to equalise exposure using ethendue that is used for optical transmission.

At constrained depth of field SNR does not depend on sensor size nor pixel size I have not determined that myself is the physics. optimal depth of field does not go into the mix

As long as you can keep the same physical aperture sensor size does not matter. At some point however the larger sensor will have the ability to process more light so the SNR is actually better at low ISO not high ISO.
The ability to take shots in dim conditions is more related to the size of the pixels when combined with a high power gain amplifier this is usually not available on a non pro camera with some exceptions (Panasonic GH5s). Still I would not use a GH5s if I wanted to shoot in the dark and put my hand on a lower megapixel full frame that can take much more amplification. Cameras like A7S also have two gain circuits and this is what makes the difference the larger pixel help retaining some DR when the ISO is really high

Sorry you started the debate saying I was obsessed by depth of field while that was not even a consideration and then you kept going with other accusations. The content never changed facts are still the same and you can make the choices you want and nobody is going to care about it

 

[HKGuns]

These aren't dive shots, but the principles apply equally regardless of venue.

DOF is important in Macro and Portrait photography. Noise gets in the way of nearly any image, regardless of subject, format or category.

This shot has pretty decent DOF and the EXIF will show it isn't shot at a very small apeture.

These are shot at very high shutter speed and the lighting makes it necessary to bump the ISO to a point where noise starts to come into play. Knowing what to use and when and having a solid understanding of post processing is just as important as the kit.

Again, the EXIF tells the full story.

 

[tarponchik]

As long as you can afford to shoot at ISO 100-200, the sensor size does not matter, they are all good. But once you are pushed to higher ISO, bigger sensors and faster lenses (and this depends not only on the aperture but also on lens complexity; the more elements you have in the lens, the less transparent it is) will have some advantage in SNR. Will you agree with that?

 

[Interceptor121]

As long as you can afford to shoot at ISO 100-200, the sensor size does not matter, they are all good. But once you are pushed to higher ISO, bigger sensors and faster lenses (and this depends not only on the aperture but also on lens complexity; the more elements you have in the lens, the less transparent it is) will have some advantage in SNR. Will you agree with that?

It is actually the other way around. ISO 100 is not the same thing on a full frame camera, on APSC or MFT or 1" in fact larger the sensor more photons are captured.

If you shoot ISO 100 on a full frame you will have less noise than APSC or smaller format the benefit because those formats can't collect the same amount of signal. This is the reason why you hear the comment my photo is noisy even at ISO 200 on a smaller sensor camera. As you move to higher values and apply depth of field equivalence the benefit of the larger sensor goes away until it reaches that point where the size of the pixels impacts DR or the smaller camera has so little signal it can no longer amplify the signal

People are mislead because they compare the wrong things. On a 2x crop at equivalent DOF ISO 800 is 3200 on full frame. So it is clear that you compare the two cameras at the same ISO value the full frame camera is less noisy but this is not what you do. This is also the reason why ISO limits are different
My MFT stops at 25600 the Nikon D500 at 51200 the Nikon D5 at 102400

The other factor is that smaller formats sometimes also lack fast lenses the typical good lens on FF is f/2.8 but you don't see many MFT 1.4 lenses or f/2 APSC though some exist

So to make the most of a larger sensor you need to shoot at the lowest ISO otherwise the benefits do not materialise. Underwater we are for most not in abundance of light but not in a complete starve as typically when it gets dark the colors are also gone and without strobe the picture looks gross no matter the format.

Completely counter-intuitive I am sure but it is the way it is. Digital camera are not film and ISO 100 on full format is not the same on another format is just a normalisation of gain to make the exposure triangle work as expected and ensure that the minimum value you see looks like 100