Rear lens cap size for Fujinon NW 125mm

I just picked up a Fujinon NW 125mm f/5.6 beauty. It is the version with 46mm front filter size (there are 52mm and 55mm front filter versions of the NW) and a 39mm rear filter thread.

The data sheets for this lens show a 48mm front push-on lens cap but do not say what the rear push-on lens cap size is.

In my experience push-on lens caps are typically at least 2mm larger than the filter thread size. This would make the required push-on rear lens cap size 41mm. However, this seems to be a size that is not manufactured by the usual brands that still produce lens caps (for example, Schneider).

Can anyone confirm what the correct size should be for a push-on lens cap to fit a 39mm rear filter thread mount?

Cheers.


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I have that lens. The original rear cap is marked inside as 39mm so I can only assume that the size goes by the filter thread. I have measured it and it is 41mm across as you have said.

For what it's worth, my NW 125mm f5.6 (52mm front thread) has an original rear cap marked "42". That is the outer diameter of the rear of the lens, and the inner diameter of the lens cap.

Please note: the Fujinon plastic caps usually have several, thin, inner plastic "columns" for a snug fit -- so the inner diameter of rear cap is 43mm, but only 42mm if you adjust for these thin "columns".

So just measure the outer diameter of the rear of your lens and get a cap with the same inner diameter.

IF it happens to be a LITTLE too large, you can put some tape on the inside to make it snug.

Kaiser is a good source of push-on lens caps