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I just purchased a Rodenstock 90mm 6.8 that the f stop ring starts at 5.6 is thi s normal and if so how do you determine what stop the lens is at. If I meter at f22 do I set the lens at f22 on the ring. I measured the iris and it is about 13 mm so I think it is a 6.8 any help will be greatly appreciated. Ross
Ross, I own the Grandagon-N 90mm F6.8 and the scale starts at 6.8 on mine. Did you purchase this lens new? Is is possible that the lens has been put into a new shutter?
I have that same lens as well and my f-stop ring starts at 6.8.
I have the Caltar 90mm 6.8 (is the Rodenstock) and although the lever goes past 6.8, it is the widest aperture marking and the iris only starts to open at 6.8. Sounds like you have a different lens. What's the filter ring size? Mine is 67mm
Ross,
Mine starts at f6.8, too. You should not worry too much about it. You neither will take pictures wide open nor will you need to set it to f6.8 for focussing. Just make it fully open to get f6.8. Your lens has probably been remount in another shutter some time. As long as your get properly exposed Pictures at f22, you may ignore this. Just make a test picture.
Problem resolved. The person I purchased the lense from made a mistake and put the wrong shutter on the lens. The correct shutter is on the way. Thanks everyone for your help Ross
"The correct shutter is on the way"
It really isn't that simple. Back focus is much more critical on wide angle lenses and spacing is critical.
If the shutters were that easily switched you probably need a qualified technician to check and add or subtract whatever shims are required to ensure that the lens functions optically as it was designed to.