Ikelite lens port chart - Dome selection

When looking at the port chart [1], for example for Canon 10-22. There is a compact 6" dome listed, and also a 8" dome option. Both options are listed for most WA lenses. However for some like the 10-22 a ** has been added to the 8" column with the caption "** Recommended".

Are they discretely trying to say that the 6" option is not good for these lenses?

[1] http://www.ikelite.com/web_pages/2port_canon.html

Cheers

/O

Larger domes generally perform better than small diameter domes because they cast the virtual image farther out and utilize a more practical area of the focusing range of the lens. They also typically have a more gradual curve so the virtual image is flatter, also better for a flat field lens. You can expect sharper corners. I would be leery about using the 10-22 lens behind a small dome.

I have only used the 8" dome with this lens. I had very questionable results, the corners where invariably soft. I read quite a few posts on adding Diopters etc but nothing seems to have really worked for the authors. Anyway my problems where solved (!!) for me by a flood, which ruined the 10-22. Which was a pity as it is very versatile piece of glass topside. I am now using a Tokina 10-17 which seems to be a far better lens underwater. I have only dived a few times with it but the results are very impressive behind the 8" Ikelite dome.

As pointed out in the previous post, the 10-22 already suffers from corner sharpness so best go with the 8". Maybe one of the other members has tried both setups.