technically speaking what are the advantages and disadvantages of the APSC and full frame cameras?

clearly bigger sensor and more pixels with full frame, but beyond that are there any specific technical or optical matters of relevance to UW photography?

Mike S

I've used both, Mike.

Like so many things with underwater photography, what you can achieve in that environment and what the two cameras might be capable of, are two different things.

I used a D800 (FF) for about 4 years and a D500 (APS-C) for 9 years. Other than having more pixels to crop, I honestly could not see the difference for the types of images I use: selling to stock agencies, on my computer, sending to friends, the occasional A2 print....

For me, and I'm sure others will argue, the disadvantage of FF is the size of the gear, the extra difficulty of housing a rectilinear with a huge port - and the cost of the lenses. I know wet lenses can make a difference for wide-angle and might be easier to "house".

For that it's worth, I would not go back to FF. I'm actually moving down again to M43!