Over under issues

Hi all,

Gear is:

Canon 5D mk3
Sigma 15mm/2.8 Fisheye
IKELITE housing
IKELITE dome 8" + wide angle adaptor/tube

Struggling to get over part of image focused, underwater part is well focused, is this a tube length focus issue or my stupidity?

Many thanks for any help.

You need to stop the lens down to maximize the depth of field. If your underwater subject is very close you will not be able to get near-infinity sharply in focus too.

Thanks Tom, I am pretty sure that is my stuoidity, I just checked the EXIF and the test shots at an indoor pool (!) were f4.5, nowhere near enough to encompass both focus points.

Thanks again, Scott.

I'm interested in trying some over under shots and have seen suggestions that an graded ND filter helps with over under pics. What value ND is recommended?

Thanks,

Mark