I am currently using Sony A6000 with Ikelite Underwater Housing with the kit lens (16-50mm), Sigma 19, 30 and 60mm and Sony 50mm macro.
I also have Canon 500d with a Sea&Sea Underwater Housing. I am using Canon 60mm macro in this setup.
The major difference between these 2 cameras are the low light capabilities, video recording quality and autofocusing speed.
If you decide to upgrade from your existing canon DSLR (I assume it is a 500d) to Sony A6500, you should notice immediate:
1) Improvement in noise performance (even in Low ISO);
2) Canon 500d Full HD video will be replaced by the stunning 4k output from the Sony A6500 with good 'autofocusing';
3) You will be able to focus using the LCD screen compares to the small viewfinder in Canon 500d. Plus the Canon 500d live view autofocus is barely usable;
4) Ability to crop pictures during post-processing thanks to the increased megapixels (this is a plus point for macro shots)
There are few things to consider:
1) My Sony A6000 white balance is not as good as Canon 500d. It is not consistent. I normally shoot RAW so this is not a big disappointment as I can adjust the white balance during post-processing;
2) Sony native E-mount lens selection is still limited and Sony doesn't seems to pay much attention to its E-mount lens. There are converter in the market which allows you to use Canon lens or other manufacturer lens, however, the autofocusing performance is questionable;
3) Sony A6XXX battery performance can be also an issue, some underwater housings have the option to allow the use of external battery pack. This is definitely an option worth for considering, you don't want to open the housing in between dives to change battery.
4) This sel1018 is good but not incredible in terms of image quality but sharpness generally improve when stopping down the aperture.
Sorry for my bad English.
Edited by alantsang2, 16 September 2017 - 12:30 AM.