Here are the test shots I promised. It's the Sigma 24mm 2.8 with a +4 diopter, behind the Subal 4" compact dome port. Just about usable down to f8, any wider and corner unsharpness and vignetting increase dramatically.
However, when you're shooting close focus wide angle, it's a different issue (my static fish @ f2.8)
I made some unscientific test shots in the pool the other day, to see how the Tokina 10-17 FE performs on a 24 mp full frame camera behind two different dome ports.
Camera: Nikon D600, Tokina on 15mm, ISO 6400 (ambient light), Aperture priority. Focus point was at the center. I ran the raw files through Lightroom to adjust white balance and lighting. No cropping, sharpening or noise reduction were applied. I sharpened for screen upon exporting to jpegs.
First three shots using the Tokina 10-17FE behind Subal 4" minidome (DP-54 B)
Last three shots same lens behind Subal 6" dome (DP-SW B). No extension rings.
I guess f11 is the limit. At 15mm behind the 6" port the dome shade is visible in the corners (slight vignetting), limiting it's use to the long end.
not exactly the same lens, but I use a Sigma 24mm f2.8 macro under water for small landscapes, animal and diver portraits (see example), in combination with a +4 diopter and a 4" minidome. I like it a lot. Topside it's great, too.
Posted by rumblefish
on 23 February 2013 - 10:48 AM
+1 for the 60mm macro if you're on DX. It's very versatile, I use it in combination with an extension tube and it gives me the opportunity to shoot fish portraits, small dioramas and macro in one dive.
Switched to full frame now, had some fun this afternoon experimenting with macro setups. I learned that a reversed 50mm 1.8 on a Sigma 180 macro works well, see test shot below of the tip of a 0000 paintbrush (uncropped). Not sure how this would work under water though.