Diopter needed for the Sigma 17-70 lens?

I purchased the Sigma 17-70mm lens but have not used it diving. Do I need a diopter for use in a 8" domeport? If so, what size? No. 2, No. 3 or No. 4? I have a Nikon D7000 with a Nauticam Housing.

Thanks,

Kandace

No dioptre needed, it can focus close enough. Don't need a dioptre with a 6" dome either.

No dioptre needed, it can focus close enough. Don't need a dioptre with a 6" dome either.

I use the Sigma 17-70 HSM macro in the Nexus 170 mm dome port (6.7") and spa tub testing says it will work in the 4-1/3" Bare dome without a diopter. That is one reason why this lens is so popular.

Bob

Thanks . . .