Rollei 2.8D question regarding taking lens assembly
I really hope someone here can help me figure something out...
I have a Rolleiflex 2.8D, with a Schneider Xenotar 2.8/80 lens.
I'm experiencing a fair share of inward running field curvature from the centre to the outside of my frame.
My 2.8D is not pristine, and it had some work done on it...
Part of my question is, should there be a thin flat washer behind the front lens assembly. ie the part one can screw off the front to access the shutter blades.
I'm talking a very thin washer, if thats even the right term for it.
I haven't seen it on my other Rollei, be it a 3.5 Tessar lens. My friend, who fiddles with Rolleis, doesn't recall there being one either.
Taking the thing out doesn't really make a difference.
Example of the washer bellow...
I have yet to develop the film where I have screwed the front lens out a fraction ( about 0,5mm or less), just to see if there is any difference in the curvature.
I have originally calibrated my centre focus using a split screen and high magnifying loupe to get the centre right, which is sharp, no doubt about it.... however, the edges always focus in front of where the centre is focused.
Please visit a folder (LINK) on my ftp server, where I have two 1600ppi scans from my Imacon showing the effects.
Both images are focused behind infinity, and images were shot at f/5.6.
I live in Namibia now, a place even more backwards than South Africa, which is where I moved from (Cape Town more specifically). There are no decent or reputable repair shops around, and South Africa is filled with plenty of camera butchers. I don't really want to send my camera in. It's just not worth it. I'de rather try and find another Rollei at some point...
Can anyone confirm what the deal is with the washer, and whether it belongs there or not, and if it does belong, what the appropriate thickness may be.
The repair guy who cleaned and serviced my shutter a few years back, admitted to having lost the original ring, and replaced it with a new one. Whether or not the thickness correlates or not is my concern, and whether it is responsible for this curvature of field...
Anyways. Thanks in advance for the help.
I've not seen such a washer on my 2.8C Xenotar. Or behind a 2.8A Tessar, or behind a variety of 3.5 Tessars and Xenars. No washer behind the front lens group on any Minolta Autocords or YashicaMats, either. Or Zeiss Ikonta Tessars.
Have you simply removed the washer, screwed the front element back in as far as it will go, and then made shots? Every lens I have ever disassembled that goes on a leaf shutter like a Synchro-Compur has the front and back blocks simply screw onto the shutter body without any washers or spacers. Proper lens spacing is designed in to the mounting, not adjusted by washers or such.
That washer looks like one that would go behind the shutter. I'd have to dig out some notes, but I think that there is usually a brass one to the front side of the lens board and a blued steel one to the back side of the lens board captured by the rear retaining ring/light shield (you can see this as a ~15mm(?) tall tube inside the camera).
There are repair people out there who would probably give you a simple yes or no answer with some better photos and explanations of where you found the washer. Most of the ones I have dealt with are helpful people who would understand your location and problems with shipping and might provide a simple yes/no answer as to whether they have ever seen such a washer in the position you describe.
Last edited by Dan Daniel; 05-02-2013 at 12:07 AM. Click to view previous post history.
Thank you Dan.
Your reply already helps a lot. I have removed the washer, and have tightened up the front element.
I have taken test shots, which I hope will be good enough to see any variations in curvature. Some shots done with the lens rotated out a fraction, and some with the front element screwed in completely without a washer. I also tried to compensate for the shift in focus due to the adjustments, so I'm hoping I did it correctly, and within usable margins. Time will tell.
As far as I know, the camera has not had the lens assembly completely disassembled. However, I'm not skilled enough to disassemble the Rollei and put it back together, so I couldn't tell you about the state of washers behind the shutter.
The scans will hopefully settle my curiosity as to how the position of the front element affects the curvature of field, if at all... If I cannot see any differences, then I need to either live with the curvature, or find myself another Rollei, which is near impossible down here... Its just a complete pain in the but to deal with the curvature for landscape shooting, especially if the problem isn't largely corrected for by stopping down to f/8.
My 20 year experience with a 2.8f leads me to the following suggestions:
Originally Posted by hmzimelka
Many 120 rollfilm cameras don't always hold the film flat in the middle, but the edges are held in place. That slight bulge in the middle makes the center focus farther away than the edges. This is probably what you are experiencing.
Indeed, a shim on the front cell will change curvature by making the perimeter of the field focus farther away and having not much effect on the rays near the center of the optical path. However, without using the Rolleiflex glass plate accessory to hold the film flat, your results of testing lens spacing will be subject to errors.
I'd just put the shim back where you found it.
The washers behind the shutter are not critical to the functioning of the camera. As long as the film wind and shutter cocking works, I wouldn't worry. If any of the washers are shims for lens infinity setting, there are other ways to achieve this. Your primary issue is to get rid of the softness in the center of your images. The Xenotar should NOT be giving you images like your links.
Take out the washer and tighten the front lens group into place, finger tight is fine. No 'fraction' out or such. 0.5mm is not a small amount in optical systems!! Rollei's spec for alignment of the lens board to the film plane is 0.05mm (1/20thmm, one-half of one-tenth of a millimeter, .002 inch) maximum difference between the four corners of the film plane, and it is this large because you are dealing with depth of field and such. And this large a number assumes a precise optical/shutter assembly, which comes about from machine work, not random washers and shims.
Once you get the shutter block properly assembled and giving you relatively flat focus plane, correcting for infinity focus isn't hard, and getting the viewing and taking lens in alignment isn't hard. But none of that is worth much if the lens is giving you poor images.
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Ic-racer, thank you for your comment.
The issue of film not lying flat had crossed my mind. However, the Rollei infrared film, and also some of the other Rollei films, are films that have the least curl I know of. Both vertical and horizontal. The horizontal curl is often such that the emulsion would, if anything, tend to curl in the opposite direction to the lens, pushing the centre into the backing paper. I've had a warping issue once with Tri-X, but thats the only time I observed the effects of in-camera film warping. My other Rollei doesn't display any strange or strong filed curvature issues. Somehow, I tend to think it can't just be the film. I have shot many different brands, PET or triacetate, thick and thin emulsions... on the 2.8D, the behaviour has always been the same.
Regarding what you said about the front element position; Do I understand you correctly, that moving the element away from the shutter, that the perimeter will focus further towards infinity while the centre will largely be unchanged? ... In my case, mitigating the curvature I'm experiencing? I don't understand enough about optics to imagine the result of moving one element or group of a lens.
I'm wondering if one of your lens elements (or groups) is installed incorrectly. Look up lens diagrams and check that everything is installed in the proper order, in the proper alignment. You mentioned camera butchers in SA - I wonder if one of them got their hands on it in the past and switched something around that they shouldn't have.
Dan, the viewing lens is fairly well calibrated to the taking lens, in that I get the centre sharp when I need to. The examples were simply deliberately back focused to emphasise the relation of the centre to the edges.
I have removed and stored the thin washer/shim from the lens. The front element is seated securely. I can't draw any conclusions from my test image, and I will have to shoot a few rolls and see. By the test image HERE,
It seems it may be slightly better now, or I may be imagining things. Differences between centre and edges are still visible at f/5.6, and the differences appear to be symmetrical.
(the mountain's edge is further away on the right than the focused centre) The skew light pole is about a meter behind the white wall on the left.
Last edited by hmzimelka; 05-02-2013 at 12:04 PM. Click to view previous post history.
I'm afraid I'm not sure how to determine if the order is correct or not, as I cannot disassemble my Rollei without fearing that I may never be able to put it back together again.
Originally Posted by TheFlyingCamera
Under correction, the camera has only had it's focus screen modified, which was done by someone with two left hands, and I had it's shutter serviced. This focus screen installation was probably a DIY attempt by the previous owner. Besides the focus screen and the repair chap who cleaned the shutter, I don't think the lens assembly has seen any disassembly. No paper trail to back that up, so anything is possible
The lens cells would have to be removed to access the shutter for servicing, so it is possible they were put in wrong. If you're that concerned about it, I'd ship it off to someone in the US or the EU to have it properly serviced (even with the shipping cost, it will be worth doing, as the camera seems to otherwise be functioning). I have a 2.8E that I bought in well-worn condition that needed a major overhaul. The servicing cost me almost $400 USD, but now I have a camera that will last me another 20 years. When you spread that cost out over the life of the camera, it comes down to pennies a day. Very economical.