With a flat port I found the dioptre worked with the 12-50 through almost all the range (from 15-50mm). Wider than 15mm it cut off.
Thank's for the information and that's good news.
With the wider view of the dome port I expect that I will have to zoom in a bit more, but should probably work at least from 25-50mm, which is good enough.
So for that purpose do you think the +5 diopter will be enough or is it better if I go directly for the +10 diopter?
I'm currently leaning more towards the +5 diopter since it will be smaller and lighter than the +10
With the 60mm macro lens I'm planning to get anyway, I think it should be good enough as I can go a bit more over 1:1 which is probably all I will need anyway.
But I may be wrong so I thought I'll better ask first