The qestion is what do I need them for while using WA lens?

We need more information. What lens are you talking about? What housing?

Most wideangle lenses built recently do NOT need diopters (also called closeup lens) when used in most underwater housings.

Cheers
James

It doesnt concern any particular lens nor housing. I noticed some discussions about the need for diopters while shooting WA. I know what you can use those filters for with macro lenses but didn’t understand why with WA. Is there any reason?

Hi Dareck,

A diopter is not a magnifying glass - what it does is brings the infinity focus of your lens in to one meter or less. Some older wideangle lenses didn't focus close enough to focus on the "virtual image" produced by a dome port, which is typically about one foot in front of your housing.

Without the diopter, the lens and camera in the housing will focus fine when testing or playing around with it above water, but once the housing is put underwater, the dome acts like a lens and changes the optical properties of the system. Without the diopter, it might not be able to acheive focus at all.

Most new lenses can focus closer than a foot so don't require the diopter. It varies from lens to lens and port to port.

HTH
James

James,

Thank you for the explanation. I started to think that it might be some tricky technique I dont know

Cheers
Darek