5 hours ago, Chris Ross said:

There are a number of constraints when using lenses behind water contact optics, there is an entrance pupil constraint and there are also issues with zoom lenses that change length as they zoom

I looked into using the z24/1.8 with the wwl-c a while ago and this was the issue. Front element cause vignetting.

Edited 12 hours ago12 hr by Christian K

3 minutes ago, Christian K said:

I looked into using the z24/1.8 with the wwl-c a while ago and this was the issue. Front element cause vignetting.

Yes, it's unclear exactly what sets this and it varies between the WWL and WACP models as to which lenses they work with. I would guess that port charts for these optics are fairly complete and to get a better optic use the chart to help, but probably involves going to a WACP. I would think that the main limitation with some of these bigger lenses is the flat port size (port ID or the m67 port diameter causing vignetting), or some of the small primes a short enough port to properly accommodate them.

9 hours ago, Chris Ross said:

The other advantage of the wet optics is that shooting at f5.6-8 is possible where the corners would be pretty mushy on a rectilinear behind a dome.

Very good points, Chris. Put differently, it is a bit like working with an upscaled image that is almost APS-C in size. Because you are using only the center of the optical system, the “corners” improve — although they are not really true corners anymore — much as they would if the photographer had simply cropped from the center of the image.

So if one wanted to frame it positively, the credit for the improved corners and the straighter rendering arguably goes more to the air lens and its lens corrections than to the water-contact correction optic. 😉

The obvious downside, of course, is this: why take an expensive and bulky full-frame system underwater if you could achieve similar image quality with a more affordable and compact APS-C setup?

Looking at the WACP - calculations show that this is closest to a stereographic projection fisheye,

Interesting - where did you find that? I’d really like to dig into those calculations.

Edited 4 hours ago4 hr by Adventurer

7 hours ago, Chris Ross said:

Yes, it's unclear exactly what sets this and it varies between the WWL and WACP models as to which lenses they work with. I would guess that port charts for these optics are fairly complete and to get a better optic use the chart to help, but probably involves going to a WACP. I would think that the main limitation with some of these bigger lenses is the flat port size (port ID or the m67 port diameter causing vignetting), or some of the small primes a short enough port to properly accommodate them.

Yeah, I’m not sure the WACP route will yield any gains that are really worth it for me compared to the WWL. Maybe if I start shooting at home in the Baltic Sea regularly… that does not involve flights.