Canon lens test - Trying to help a friend

I have a friend and Seacam client in Norway shooting orcas at the moment. It is a challenging shoot because there is very little daylight, forcing him to shoot nearly wide open at high ISO to be able to stop the action. It is impossible for him to do a pool test so I thought to do a semi-controlled test of 2 possible lenses he might use. We already have good data on the 16-35II and recommend a 57.5mm port extension and Superdome for that one, but it was worthwhile to try to dial in the new 24-70mm II F-4 L IS and the 14mm II F-2.8. I wouldn't use either lens at F-4 normally, preferring instead to get to F-8 or smaller, but as this is the world he is forced into at the moment the challenge became to get the best we can out of corner performance at F-4. Canon 5D3, Seacam housing, swivel 45 viewfinder (no reason to get all the way wet on this cold morning), Superdome, Wideport, and either a +2 or +4 diopters were tested (only the 24-70mm II F-4 L IS would accept diopters of course)

The results came out looking like this:

But, I guess the final analysis is with enlarged views of the corners.

Canon 14mm II @ F-4:

14II_PVL20_superdome

14II_PVL20_wideport

14II_PVL30_superdome

14II_PVL30_wideport

comparison with PVL 20 on the left and PVL 30 on the right

All are very, very sharp in the center but do fall off in the corners. No surprise about that at F4. However, the PVL20 is better than the PVL30, and the 9" superdome is far better than the smaller wideport. The only time I'd use the wideport with the 14mm II lens is when snrkeling with big animals and you have to lose water resistance, and are willing to sacrifice corner performance. In any diving scenario, the 9" superdome is far superior.

OK, now the 24-70mm II F-4 L IS. This is a new lens to me so I have no data at all. But, here's what the tests reveal:

24-70_PVL35_superdome

24-70_PVL40_superdome

24-70_PVL45_superdome

:24-70_PVL50_superdome

PVL 45 is the best with the Superdome

Now the same with diopter, both Superdome and Wideport:

24-70II_PVL40_superdome_+2

24-70II_PVL40_superdome_+4

24-70II_PVL40_wideport_+2

24-70II_PVL40_wideport_+4

Note significant Field of View loss by using a diopter, and the greater the strength of the diopter the more the wide angle field of view is compromised. This should be well known by now. But, if we are strictly looking at corner performance the diopter does help, although at the expense of additional chromatic aberration. Still, it seems the best corner performance is achieved with a +4 diopter, and the Superdome is still significantly better than the Wideport.

If you can stand the loss of field of view, accepting that software can correct for chromatic aberration, the Superdome and a +4 diopter would be a good solution. But, if you need your 24mm to be 24mm, use the Superdome and PVL45 without a diopter.

Ok, so here is the final observation from this test, the optimal port extension for 24-70mm II F-4 L IS and also the +4 diopter, both on Superdome. Note differences in corner performance and field of view:

24-70_PVL45_superdome

24-70_PVL40_superdome_+4

If you need to work wide with this lens try it without a diopter, but still try to get F-8 or smaller for a working aperture to achieve reasonable corner performance. For reef fish, accepting that you'll be tighter on the subjects, the +4 diopter is quite nice.

Great post Stephen.

Thank you for sharing your results with the Wetpixel community.

Adam