Using the "wrong" extension tubes in a bind

On a recent dive trip I didn't follow my checklist and forgot to pack the extension ring for my Aquatica 8" dome port. I did have the ring for the 105 mm macro flat port, so I just used that and the WA shots seem to be fine. The flat port ring is slightly longer than the dome port ring.

Now that I'm back home, I can't seem to find the dome port extension ring so it looks like I'm stuck with the flat port extension until I can get a replacement.

I don't see any noticeable focus or softness issues using the macro port ring. Has anyone else ever had experience using a non-specs extension ring when in a bind?

It seems a lot easier to pack one less extension ring, especially nowadays when weight and space on puddle jumpers is more of an issue.

Or am I missing out on optimum optics by using the slightly longer extension ring with the 12-24 DX and 8" dome port?

Hi,

When this lens first came out, I ordered one from Hong Kong and Aquatica sent me various rings to try out with it.

I tried the ring for the 18-35, the ring for the 105, the short ring (15mm) that is now recommended for the 12-24dx and even a couple of combinations of 2 rings.

I found that it made a BIG difference in the lower corners. I started with the ring for the 18-35 but found the corners too soft for CFWA. The longest combination was just longer than the ring for the 105 and it resulted in vignetting.

This lens is very touchy and requires the correct ring for good results, in my opinion.

HTH

James Wiseman

Thanks, James. Just the info I was looking for. Looks like I'll be shelling out for the 15mm extension ring again.