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Hi all,

I am a new user and found this forum while searching for info on a lens: the 21cm f4.5 luminant. I quickly found out it was made for the rittreck/optika SLR. A bit of a dissapointment to me, as I intended to use it on a 4x5/5x7 camera. However, having put it in front off the camera it seems to illuminate the whole groundglass :D

While the lens is in quite nice shape, and has the extension tube, it does have a problem: the iris won't close. I have a bit of experience with repairing shutters etc, so I opened the lens up to take a look. I however can not figure out how the iris is supposed to work. The iris leaves are only attached at the bottom, there isn't anything at the top that pushes them open or closed when turning the aperture ring. Turning the aperture ring does turn the inner ring, but the inner ring doesn't move the blades!

Any help with this issue would be welcome. Maybe a part is missing? An exploded parts diagram/repair manual or something alike would be great!

Also, does anybody have an idea on the price of these things? It is quite useless to me and if it is actually worth something I'd rather reinvest in a proper large format lens, rather then hacking this lens up for my experiments ;)

One last question is wether this lens is the same as the fujinar 21cm f4.5, or different?

Thank you,

Wim Abbeloos

Wim,

I don't know the 21cm Luminant but it might be a preset lens, just like the Luminon 105mm on my Optika camera. On the Luminon, when I turn the aperture ring and set it to F/11 for example, the diaphragm stays wide open. This feature is designed to provide a bright image in order to allow easier focusing on the ground glass. To actually close the diaphragm just before taking the picture, I have to turn a smaller black serrated ring with an index tab, which is located in front of the aperture ring. This black ring has no scale and needs to be turned all the way to close the diaphragm to its preset aperture. Maybe this ring is missing in your lens?

Hope this helps,

Sebastien

I'm pretty convinced all external parts are present, and that it is not a preset lens.