Rodenstock 210 Geronar lens; low quality or mechanical problemgreenspun.com : LUSENET : Large format photography : One Thread
The 210 Geronar was the first lens I purchased upon getting involved with large format. I seem to be having problems getting things in sharp focus around the outer edges. Do you think my lens may be of low quality or could it be something mechanically? Please respond and thank you for your time.
-- Ricky Smith (email@example.com), January 01, 2002
On film or via loupe when focusing wide open?
At what aperture?
-- Bob Salomon (firstname.lastname@example.org), January 01, 2002.
How much are you stopping down? My first LF lens was a 150mm Geronar, and while it isn't/wasn't the sharpest lens I've ever used, I never had much of a problem with sharpness around the edges unless I didn't stop down enough. The effect may be more pronounced with the longer focal length, but I really don't know for sure.
-- David Munson (email@example.com), January 01, 2002.
Ricky: With any reasonably modern professional quality lens having focus problems, the first place to look closely is under the dark cloth to see if you are doing everything right. It is easy to get a bit sloppy with critical focusing. Next, check the camera ground glass to see if it is seating properly and think if you have done anything to affect the relationship of the ground glass to the film plane, such as add or subtract a Fresnel screen. If you bought the lens used, try to determine if the shutter is original. If it has been changed, the spacing may not be the same between the lens cells. With a view camera, make sure the standards are centered and aligned. With many, if not most, lenses for view cameras, the larger aperatures are for focusing only. Try shooting at aperatures of f-11 or smaller. Are you positive the lens is clean, especially the rear cell. A juicy fingerprint on the rear cell can act as a diffuser. Check also that you are not focusing too far into the scene. Most lenses have a bit of curvature of field, and it is better to focus nearer and let the depth of field carry the focus for greater distances. Hope this helps.
-- Doug Paramore (Dougmary@alaweb.com), January 01, 2002.
Its hard to say whether your lens has a problem or not, but I do not think that you will find that these lenses are low quality as a general rule. I have the Caltar II-E 210mm version and find it is a very high quality lens. Some of my favorite images were taken with it. They are quite sharp. The Caltar II-E is Calumet's version of the same lens, manufactured by Rodenstock. (In case you have any doubts, it comes in a Rodenstock box. Also, check other threads in this forum.)
-- Dave Karp (firstname.lastname@example.org), January 01, 2002.
you should check if the lens is mounting properly, sometimes there is a little screw under the shutter, it's suppose to be use to be put in a little hole on the lens panel to prevent twisting, but if there isn't a hole on the lens panel, you have to remove it before mounted it ! My english is not very good, so if someone else that knows this problem can explain it properly...
-- dg (email@example.com), January 02, 2002.
from schneider optics FAQ :10. My Schneider lens has a small protruding screw in the back of the shutter that prevents the lens from sitting flat against the lens board. What should I do?
In order to prevent the lens from rotating in the lens board, a hole can be drilled into the lens board to accommodate this screw. Once the screw is mated to this hole, the lens will stay in one orientation. The screw can also just be removed with no ill effects on the performance of the lens.
-- dg (firstname.lastname@example.org), January 04, 2002.
Any Tessar design lens will be fuzzy at the edges unless stopped down...
-- Alan Cecil (email@example.com), January 05, 2002.