View Full Version : Xenar 135mm lens

9-Dec-2008, 04:21
I acquired this lens some time ago without the aperture markings on the face - is it possible to get hold of something that I could stick on the front as an indicator, or make something myself?

If anyone has a similar lens, would it be possible to scan the aperture scale - I could print it out and attach it to the lens. I'm not worried about it looking very pretty!



9-Dec-2008, 04:44
I always thought you could probably figure one out with a dark cloth, a spot meter, and a uniformly lit wall... point the lens at the wall, open the lens up (and assume it is the maximum aperture specified on the lens) then take a spot reading (in EV, shutter, or aperture - we're just interested in relative readings here)... then close the aperture a bit while spot metering until you've lost a stop of illumination and mark the front of the lens at that point as one stop closed... continue to 2 stops under the reference reading and mark that two stops closed... etc.

Am I wrong here?

I can't see how this wouldn't work accurately enough for pretty much any regular lens usage / exposure situation, except that you'd have to make sure you read the same point on the GG or did an average reading (and had no light spilling in under your dark cloth). Control everything carefully and maybe run the tests a few times and average out the tick marks on your aperture scale if you are especially anal.

Dan Fromm
9-Dec-2008, 07:50
Matt, the last time I was at SKGrimes I asked Adam how he scaled apertures. He told me that he calculated the size of the entrance pupil for the apertures to be marked (in your case, /4.7, /5.6, ...), then adjusted the aperture until the entrance pupil was the right size for the first one, marked, and so on.

Walter, I've tried a procedure roughly equivalent to yours. I hung a lens in front of a Nikon with TTL metering, set the lens wide open, found the shutter speed that centered the meter, marked, dialed a shutter speed half as fast, adjusted diaphragm to center the needle, ... The results weren't precise or repeatable. Direct measurement as Adam suggested seems better.

Nathan Potter
9-Dec-2008, 08:08
Walter, I've done what you suggest in my darkroom using a wooden box and a small light table. Mounted the lens on an old wooden camera and metered the GG on axis. Checking the light levels against known lenses shows pretty good accuracy to better than 1/3 stop. You have to exclude external light from reflecting off the GG though. Course accuracy is also subject to the linearity of the meter.

Nate Potter, Austin TX.

9-Dec-2008, 09:55
Matt, I've just drawn a scale that matches the one on my Compur, and will email it to you, can you PM me with your email address. I

How's that enlarger I gave you :D


9-Dec-2008, 10:10
Thanks everyone for your replies.

Ian - I've sent you a PM