a tale of two octopi

I had an unprecedented (for me, anyway) opportunity a couple of weeks ago to shoot portraits of two relatively cooperative reef octopi. As luck would have it, it was my first outing with a new lens , the Panasonic 7-14 behind a Nauticam 6" dome. The octopi were in a crevice, open at both ends, that was a cleaning station. I got one shot with an octo that was in focus, and one with a shrimp that was in focus, but nothing where both were clear.

These were shot at f8 so I should have stopped down, obviously, but how far could I have gone and maintained good IQ? Advice welcome.

The octopi took turns swapping places as I disturbed them with strobes. And since the alpha shrimp is posed identically and someone is probably going to ask if I was sure there were two of them, here's the only (lousy) shot I got with them in the same frame.

I really like the second image here i think the octopus creates a nice negative space around the shrimp and helps it stand out. As for the aperture i usually stop down to between f11 and f16 if i need to maintain good depth of field through out an image. However i shoot with a completely different set up. Maybe it would be useful to do some experiments of your own setting up a measuring tape and fixing your camera position while adjusting the aperture and testing the depth of field, diffraction and overall image quality.

Thanks for your comments. I also like the second shot, in fact, the first one is blah but the shrimp is very sharp! If I had any Photoshop skills at all, which I don't, I might try swapping the two shrimp. Thanks also for the test suggestion - I will have to try that.

I usually shoot at f16 or higher for macro (which has been 95% of my experience) but I read somewhere that this WA lens does not perform well at smaller apertures. I will have to experiment to find out if that is true. I should have done it on this dive!

I do agree with Triggerfish, the 2nd pic is a masterpiece

Agree that the second shot is great. Generally the advice is that diffraction sets in at around f8 but my experience is that correct focus trumps "sharpness". If something is out of focus it will not be sharp anyway.