Using SMC-1?

Barmaglot_07 wrote:

Yes, it will work in air, or you can fill a kitchen sink with water and dunk the end of the port inside - no need to submerge the whole housing. Unless your diopter is very weak, to the point of not being useful with your lens, you don't need much water to play with the entire available range. Nauticam quotes the working range for SMC-1 with 105mm at 53-95mm, so in American terms, two to just under four inches from the front glass.

Just an extension to your advise Barmaglot:

The situation in air may be similar, but is certainly not the same when the lens is immersed in water. This is because the fraction of refractive index of the medium (n=1 for air; n=1.33 for water) divided by the refractive index of the lens glass (not known in most cases; typically 1.48 - 1.76 for optical glass) is a factor to multiply with the value obtained just by lens geometry. This is the reason why all UW optics has to be calculated separately for water immersion and is not valid above water (therefore real UW optics are so rare, the Nauticam closeup lenses belong to this species). In case the index of the optical glass used is high, the error is small and results are similar, when the index is low the error becomes big (meaning that the difference between water and air depends on the peculiar lens used and cannot be predicted without knowing the refractive index of the glass (a value that I never obtained from any company))...

=> testing in air is a first step, but then testing immersed is required to approach real live...

Wolfgang