I just bought the zen 230mm for the 16-35, and I am in the same crossroads as you are, dont know if It is a better choice sigma 15 or nikon 8-15. I know the sigma doesnt need anything extra, but the 8-15 needs a zoom gear on my nauticam. If I get the 8-15 will the shades of the 230mm dome show up in 8mm?? Do I need to get the 100mm dome for it?
Yes, the shade will be seen in 8mm pix. At 8mm the angle of view is almost 180 degrees all the way around the image and not just at the diagonals as at 15mm. Find out if the shade can be removed - many can.
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