mr.deadly Posted November 4, 2011 Share #1 Posted November 4, 2011 Advertisement (gone after registration) Hey everyone, I've had my m8 now for about 3 months and though I'm really enjoying it, I think I've run into a bit of a problem. I've done quite a bit of testing and I believe that the camera seems to be the source of a back-focusing issue. The rangefinder patch will appear to be in optimal contrast and alignment, but when reviewing the images they'll be out of focus by about an inch. I.E., when shooting a portrait, I'll focus on the eyes and the ears will be sharp. At the moment, I only have three lenses, the Zeiss 25/2.8, the Jupiter-8 50/2 and the Voigtlander 35/1.2 II. I've had the Jupiter-8 from years ago when I had a Voigtlander R2A and it was the first lens I used on the m8. The back-focus was pretty noticable and I think also aggravated by the lens having slight focus-shift. So I went ahead and got the Zeiss 25/2.8 and the back-focus problem seemed to magically go away! Well, almost... see, about two weeks ago I got the Voigtlander 35/1.2 II and now I can notice the back-focus more than ever!! So this leads me to believe that it must be an issue with the camera. It seems like the 25/2.8 larger depth of field covered up the back-focus issue, but the 35/1.2's shallow depth exposed the issue to the max. That being said, I have no way of telling for sure because I don't have another fast lens that I can try on my camera. I mean, it's definitely possible that both the Jupiter-8 and the 35/1.2II suffer from focusing issues, but that seems less likely. I've yet to read of a report of the 35/1.2 II having a backfocus issue, or any focus issue at all. Any thoughts or suggestions would be appreicated! I reeeally don't want to have to send away my new 35/1.2 II if I don't have to. Link to post Share on other sites More sharing options...
Advertisement Posted November 4, 2011 Posted November 4, 2011 Hi mr.deadly, Take a look here Backfocus anyone!?. I'm sure you'll find what you were looking for!
brianv Posted November 5, 2011 Share #2 Posted November 5, 2011 The Jupiter-8 typically requires the shim to be changed to focus properly on a Leica. It is noticeable on an M8 or M9, pixel-peeping. The Voigtlander 35/1.2 is optimized for the Voigtlander and Zeiss film cameras. Every manufacturer makes assumptions about film curvature, and sets their lenses to compensate. The M8's sensor is flat. I added one layer of copper tape to the RF cam of my 35/1.2 and 50/1.1. Brought the lenses into alignment with the M8/M9. The J-8: typically thickening the shim by ~0.12mm does the trick. The Math is here: http://rangefinderforum.com/forums/showthread.php?t=111193 Link to post Share on other sites More sharing options...
Guest #12 Posted November 5, 2011 Share #3 Posted November 5, 2011 ... http://rangefinderforum.com/forums/showthread.php?t=111193 can't follow your link Link to post Share on other sites More sharing options...
mr.deadly Posted November 5, 2011 Author Share #4 Posted November 5, 2011 The Jupiter-8 typically requires the shim to be changed to focus properly on a Leica. It is noticeable on an M8 or M9, pixel-peeping. The Voigtlander 35/1.2 is optimized for the Voigtlander and Zeiss film cameras. Every manufacturer makes assumptions about film curvature, and sets their lenses to compensate. The M8's sensor is flat. I added one layer of copper tape to the RF cam of my 35/1.2 and 50/1.1. Brought the lenses into alignment with the M8/M9. The J-8: typically thickening the shim by ~0.12mm does the trick. The Math is here: http://rangefinderforum.com/forums/showthread.php?t=111193 I'm definitely more interested in making sure the 35/1.2 works, the Jupiter-8 is more of a lens to play around with. Do you think you could elaborate on how to go about adding the copper tape to the RF cam? I'm still sort of new to the whole RF game. Link to post Share on other sites More sharing options...
brianv Posted November 5, 2011 Share #5 Posted November 5, 2011 rangefinderforum appears to be down, hopefully the link will work when restored. I use copper tape as it is durable- and about 0.05mm thick or so. http://www.ziforums.com/picture.php?albumid=263&pictureid=2943 The application is the same shown on this Industar-61. One layer on the RF cam acts to push the RF follower back "ever so slightly". The result is the RF indicates the focus is a little bit more toward infinity- brings it into agreement with the actual focus of the lens. Taken with my V1 Nokton 35/1.2 on the M8, with the copper tape on the RF Cam of the lens.: Link to post Share on other sites More sharing options...
DOUG66 Posted November 5, 2011 Share #6 Posted November 5, 2011 There have been a number of threads about backfocussing here and in the customer forum. If you search under my user name they should come up. I have corrected my own Summicron 50/2 and a Jupiter 50/2 belonging to a friend, by replacing the shim collars with ones of the correct size which I turned up from Bronze. The Summicron required an increase of 125 microns. The Jupiter was miles out, it contained two collars of aluminum as and I suspect it had previously been fiddled at. I can not remember the size of the shim as I adjusted it to suit a film camera, not an M8. Note that both these lenses exhibit focus shift with F number. If you send me a PM with your postal address I can let you have a copy of the testing chart which I designed for measuring Back/Front focus. Doug. Link to post Share on other sites More sharing options...
Dougg Posted November 6, 2011 Share #7 Posted November 6, 2011 Advertisement (gone after registration) I agree it's most likely a lens calibration matter. After I got my M8, I gradually had most of my lenses coded and checked for focus by DAG, who commented that most needed focus adjustment. Once adjusted to spec, they have focused correctly on another M8 and an M9, so at least for me it was the lenses that were off, not the bodies. Worth noting the digital M bodies are more particular about accurate focus than film cameras. rangefinderforum appears to be down, hopefully the link will work when restored. This morning when refreshing an RFF page I got a notification that equipment was being moved from one city to another in the mid-west, starting Sat morning, and expected to be up and running again within 24 hours. Try the posted link tomorrow... Link to post Share on other sites More sharing options...
pico Posted November 6, 2011 Share #8 Posted November 6, 2011 So this leads me to believe that it must be an issue with the camera. Hold on. Are you suggesting that that a Russian lens focus problem indicates a problem with the Leica? Good God, Man, the Russian cameras hardly focus properly among their own clones! Why in the world should a Leica bear up under the Russian non-standards? (Am I the only person whose M9 focuses properly with four lenses?) . Link to post Share on other sites More sharing options...
brianv Posted November 7, 2011 Share #9 Posted November 7, 2011 My Nikkor lenses focus perfectly with the M9. whatever assumptions that Nikon made 60 years ago regarding Leica Barnack cameras- they work on the M9. I'm thinking they must have assumed that film laid flat in those cameras. The Nikkor 10.5cm F2.5 and 8.5cm F2 are perfect on my M9. The Nikkor 5cm f1.4 in LTM- also perfect wide-open. The Summarit 5cm f1.5's, both of them, optimized for F2.8 as Dante Stella stated years ago. But I have a trick. My M8 is set "ever so slightly different" from my M9. The other manufacturers, with different assumptions: perfect on my M8, including the Summarits at F1.5. Link to post Share on other sites More sharing options...
JeTexas Posted November 7, 2011 Share #10 Posted November 7, 2011 My Voigtlander 50mm f1.1 focused great for about 6 months and then suddenly developed an inch of backfocus. However, I know it's my lens because the Voigtlander 28mm and Leica 90mm are still focusing correctly. I'd have your lenses checked first. Link to post Share on other sites More sharing options...
mr.deadly Posted November 7, 2011 Author Share #11 Posted November 7, 2011 My Nikkor lenses focus perfectly with the M9. whatever assumptions that Nikon made 60 years ago regarding Leica Barnack cameras- they work on the M9. I'm thinking they must have assumed that film laid flat in those cameras. The Nikkor 10.5cm F2.5 and 8.5cm F2 are perfect on my M9. The Nikkor 5cm f1.4 in LTM- also perfect wide-open. The Summarit 5cm f1.5's, both of them, optimized for F2.8 as Dante Stella stated years ago. But I have a trick. My M8 is set "ever so slightly different" from my M9. The other manufacturers, with different assumptions: perfect on my M8, including the Summarits at F1.5. Is there a way to tell where I should be putting the copper tape on the lens? I guess i'm not really sure where the RF cam is on the lens. I'm still very much in the learning stage of my RF experience. Link to post Share on other sites More sharing options...
jaapv Posted November 7, 2011 Share #12 Posted November 7, 2011 Nowhere. The lenses are shimmed internally. Link to post Share on other sites More sharing options...
mr.deadly Posted November 7, 2011 Author Share #13 Posted November 7, 2011 Nowhere. The lenses are shimmed internally. So what brianv did with his lens I can't do with the 35/1.2 II? Link to post Share on other sites More sharing options...
JeTexas Posted November 8, 2011 Share #14 Posted November 8, 2011 Back focus would be remedied by moving the lens elements further away from the sensor plane -- shimming under the mounting collar. Front focus would be remedied by adding copper tape to the RF cam, which would trick the rangefinder into thinking the lens was closer to the sensor plane. Link to post Share on other sites More sharing options...
brianv Posted November 10, 2011 Share #15 Posted November 10, 2011 Thickening the RF Cam pushes the RF follower of the camera back, which makes it think the distance is farther away. If the lens is focusing behind the RF without the copper tape, pushing the RF follower back the proper amount brings the two into agreement. Post a picture of the back of your 35/1.2. The 35/1.2 v1 and 50/1.1 were easy fixes. Worked for me: http://www.seriouscompacts.com/gallery/data/582/wreckage_35nokton_f12.jpg http://www.seriouscompacts.com/gallery/data/582/CSS_Tennessee_50nokton_f11.jpg not elegant, but quick and easily undone. The alternative is to remove the mount and make a shim to go underneath it. Produces the same correction. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/165580-backfocus-anyone/?do=findComment&comment=1840517'>More sharing options...
brianv Posted November 11, 2011 Share #16 Posted November 11, 2011 So- just to re-iterate, applying copper tape or something else to thicken the RF cam of the lens has the same net result as increasing the thickness of the shim of the lens. This corrects for back-focus. Accessing the RF cam is quicker and easier than making a custom shim. If you have a good supply of shims, and are good at opening up lenses- that is the way to go. If the lens is front-focusing, the shim needs to be reduced in thickness. You could file the RF cam of the lens down- but that is a last resort. I've done that with a wartime 5cm f1.5 Sonnar that was epoxied into the mount and would not come out of the focus mount. Link to post Share on other sites More sharing options...
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