Diopters?

[aquakiwi]

I was just wondering if anyone has used close-up diopters with the Sigma 10-20mm lens, its a nice lens but could do with closer focussing (right up to the dome would be nice). If so what strength diopter?

 

[bvanant]

What housing and what dome? Your results will depend quite a bit on the answer to these questions. Most folks who put diopters on wide angle lenses do so to get sharp corners, not to make the close focusing distance better.
Bill

 

[diver 85]

answer to your 1st question: reciprocal meters---

 

[aquakiwi]

What housing and what dome? Your results will depend quite a bit on the answer to these questions. Most folks who put diopters on wide angle lenses do so to get sharp corners, not to make the close focusing distance better.
Bill

I'm using a Ikelite housing for a Canon 400D with a 8" dome port, what is the best strength diopter for corner to corner sharpness or is this dependant on the zoom mm at the time.

 

[bvanant]

It depends on the zoom setting quite a bit. At the widest setting, I would use a +2 diopter and I think the corner performance will be fine.
Bill