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Photo Forum / Film Photography / Medium format / December 2004Rolleiflex F2.8 and optically flat glass
Reading the manual for the F2.8, it mentions an optional optically flat glass(beveled) that can be inserted on the existing pressure plate to make it especially flat for increased sharpness. Is anyone familiar with this and does it really make that much of a differance? I have three Rollei books and they all devote a small paragraph to this piece which makes me think it is mostly a useless item, however Rollei did put a small pocket in their camera case to carry this item around. Because it is a thin piece of glass I wonder too if they all broke making the user just give up altogether in using it. If I am wrong about this and it is deemed to be a worthwhile item, does anyone know where to get one? Dan, I saw one once in a Tele-Rollei, where it seems to me, that it might have some effect, since telephotos have much less depth of field than normal focal-length lenses. But I used the Rollei 2.8 for some years and never noticed any lack of sharpness without the glass. Admittedly, I rarely shot with it wide open--- usually stopped down at least two stops or more, but I'm very pleased with the 11X14's I made with it. Larry >Reading the manual for the F2.8, it mentions an optional optically flat >glass(beveled) that can be inserted on the existing pressure plate to [quoted text clipped - 7 lines] >about this and it is deemed to be a worthwhile item, does anyone know >where to get one? > Dan, > > I saw one once in a Tele-Rollei, where it seems to me, that it might > have some effect, since telephotos have much less depth of field than > normal focal-length lenses. But a tele has more depth of focus so a flat film plane isn't a critical as on a normal or a wide angle lens. I do agree this glass plate will probably cause more problems than it will fix.  SignatureStacey I'd worry more about dust on the glass plate than on any improvement in sharpness it might add. > > [quoted text clipped - 10 lines] > I do agree this glass plate will probably cause more problems than it will >fix. > I'd worry more about dust on the glass plate than on any improvement in > sharpness it might add. That and scratching the film etc. SignatureStacey > But a tele has more depth of focus so a flat film plane isn't a critical > as > on a normal or a wide angle lens. Explain, please. >> But a tele has more depth of focus so a flat film plane isn't a critical >> as >> on a normal or a wide angle lens. > > Explain, please. The shorter the lens, the less depth of =focus= it has i.e. the depth of field behind the lens is shallower while the depth of field in front is greater. It's why lenses like the 35mm mamiya 645 lens works better with 220 film than with 120. I bet your biogon would also work better with a 220 film back for this reason. If you want to prove this to yourself, get say a couple of medium format lenses of 50mm or less and 150mm or more, rack them from 3 meters to infinity and measure how far each lens moves in it's mount to acomplish this shift in focus distance. It's why trying to focus a short lens on a view camera is such a bitch and long lenses seem so much easier.It takes very little front standard movemt to shift the focus a bunch. With medium format lenses, the short lenses have a much finer focus thread to make this less of a problem. I like many people I used to assume since there is more depth of field in front of the lens, there would also be more at the film plane. But that's not how it works. SignatureStacey >> Explain, please. > The shorter the lens, the less depth of =focus= it has i.e. the depth of [quoted text clipped - 3 lines] > 220 > film back for this reason. Are you suggesting that the paper backing of 120 is really a bad thing? I hadn't thought of it. I should think that 220 and 120 backs would be made with different film-distance if the backing were a significant issue. Regarding the 3" Biogon - it's working very well with the Sinar back, but just today (Merry Christmas) I got the 120 6x12 rollfilm back. I'll try it out. Concerning the rest of your assertion, well I suppose I had best hit the books because intuition fails me in this case. >Because it is a thin piece of glass I wonder too if they all broke >making the user just give up altogether in using it. I would guess that most folks gave up using the glass because it was impossible to keep it clean enough. Signature---------------------------- Paul Friday Never seen this glass plate for the back. But I have two Rolleiflex and I don't miss the glass plate. There's enough sharpness the same. For sharpness, IMO it's better to have an accurate focusing knob and a hood clear. ciaO!! Signatureed io imparo... |
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