biglouis Posted May 2, 2009 Share #1 Posted May 2, 2009 Advertisement (gone after registration) I obtained a s/h Elmar 50 a couple of days ago and in first using it I noticed that I could not get the rangefinder on my M8 to coincide on infinity focus. At first, I thought it a rangefinder issue but I have tested my M8 with a range of other lenses I own and it only occurs with the Elmar 50. When I try to focus on a distant object (between 1/3 mile to 1 mile) it is almost like I can't turn the focus ring far enough I get just about there but no more and small difference between the patch and image remains. What is puzzling is that when I look at the images at 100% they appear to be in focus. See below, on an object which is probably 1/3 - 1/2 mile away. I've not owned rangefinders long enough to understand this problem but am I correct in thinking it must be the lens if this is the only lens it is happening with? What is the solution? Can a competent Leica repairer deal with this or do I have to send the lens to Solms? I assume there is no user-fix to this issue. Many thanks for any advice LouisB Elmar 50 100% f2.8 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! Elmar 50 100% f8 Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! Elmar 50 100% f8 ' data-webShareUrl='https://www.l-camera-forum.com/topic/83777-confused-about-infinity-focus-issue/?do=findComment&comment=887273'>More sharing options...
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giordano Posted May 2, 2009 Share #2 Posted May 2, 2009 If the rangefinder images do line up at infinity with the other lenses, then the problem is with the lens. Depth of field with a 2.8 lens is sufficient to mask a tiny misalignment like this at infinity and probably closer. Any competent Leica shop can make the adjustment. Link to post Share on other sites More sharing options...
farnz Posted May 2, 2009 Share #3 Posted May 2, 2009 Louis, Do they mismatch vertically, horizontally or both? (Not sure if this matters but the Wise Men of the forum might think so.) You might check the curved runner on the Elmar that guides the camera's RF lever to make sure there's nothing stuck to it that's fouling the lever's path. Also check that there's nothing on the Elmar's mounting plate that's preventing it from sitting flat against the bayonet mount. I realise that I'm clutching at straws here but it seems sensible to check the easy stuff before sending it back to Solms General Lens Hospital. Pete. Link to post Share on other sites More sharing options...
biglouis Posted May 2, 2009 Author Share #4 Posted May 2, 2009 Giordano/Farnz Thanks for the advice. As per Farnz's response I should have state the problem is horizontal alignment. The vertical is perfect. As I bring the horizontal images together they fail to meet at infinity. I think I need to find a local Lieca technician (rather than send it all the way to Solms) and I'll ask at the shops I use to see if they have someone who can do it for me. LouisB Link to post Share on other sites More sharing options...
stunsworth Posted May 2, 2009 Share #5 Posted May 2, 2009 Louis, it may be worthwhile trying the same on something that's _really_ far away - the moon comes to mind. If the lens needs adjusting I can recommend Malcolm Taylor in the UK. Link to post Share on other sites More sharing options...
marknorton Posted May 2, 2009 Share #6 Posted May 2, 2009 Louis, 1/3 mile is ample to establish infinity (IMHO), and your lens is sitting slightly forward in the lens mount compared to where it should be, I calculate about 0.005mm or about 8 times the wavelength of light. It also corresponds to a small - tiny - rotation of the focussing ring, about 1/10 of 1 degree. Depth of field will cover it, perhaps you should be more concerned how well it focusses close up. TBH, I think maintaining even this level of precision with a collapsible lens is doing quite well; I wouldn't worry about it. [incidentally, it's much better that a lens focusses just short of infinity than beyond it (lens barrel too close to the camera). This plagued my Noctilux until Leica replaced the entire mount. Up to then, set to "infinity", nothing, anywhere was in acceptable focus.] Link to post Share on other sites More sharing options...
biglouis Posted May 2, 2009 Author Share #7 Posted May 2, 2009 Advertisement (gone after registration) Louis, 1/3 mile is ample to establish infinity (IMHO), and your lens is sitting slightly forward in the lens mount compared to where it should be, I calculate about 0.005mm or about 8 times the wavelength of light. It also corresponds to a small - tiny - rotation of the focussing ring, about 1/10 of 1 degree. Depth of field will cover it, perhaps you should be more concerned how well it focusses close up. TBH, I think maintaining even this level of precision with a collapsible lens is doing quite well; I wouldn't worry about it. [incidentally, it's much better that a lens focusses just short of infinity than beyond it (lens barrel too close to the camera). This plagued my Noctilux until Leica replaced the entire mount. Up to then, set to "infinity", nothing, anywhere was in acceptable focus.] Mark That is an interesting point. Especially as close up the lens seems to be in focus and at distance, as pointed out by Giordano. I think I'll carry out some more tests but at least (thank goodness) it is not a problem with the M8 body. Thanks for all the responses thus far LouisB Link to post Share on other sites More sharing options...
Gentleman Villain Posted May 3, 2009 Share #8 Posted May 3, 2009 ARe you absolutely certain that you're not seeing diffraction? I start to see the effects of diffraction when focused at infinity about 1 stop before I'd normally see the effects when focused at a moderate focal distance. For example, I could only use my zeiss lenses at F8 when focused at infinity as opposed to F11 when focused at a moderate distance. Otherwise, diffraction would start to become very noticable. I think it's because the objects at infinity often appear very small and there aren't that many pixels covering them....so diffraction will often sneak in and make an otherwise sharp image appear slightly soft and fuzzy a little bit quicker than it would when focused on a larger object at a moderate distance. I can't tell by looking at your image what is going on....But it might be worth your while to do some focus tests at infinity using various apertures and see if it's possible to spot the exact point that diffraction starts to take a toll on infinity focused images. Just giving an idea.. . it could be totally wrong though Link to post Share on other sites More sharing options...
lct Posted May 3, 2009 Share #9 Posted May 3, 2009 With rangefinder cameras, viewfinders are optically separated from the lenses. Besides 6-bit coding, if any, the only links are mechanical i.e. a focus cam in the lens barrel and a roller cam into the camera's body. Then diffraction cannot play any role in the alignment of the RF patch IMHO. Link to post Share on other sites More sharing options...
giordano Posted May 3, 2009 Share #10 Posted May 3, 2009 ARe you absolutely certain that you're not seeing diffraction? I start to see the effects of diffraction when focused at infinity about 1 stop before I'd normally see the effects when focused at a moderate focal distance. For example, I could only use my zeiss lenses at F8 when focused at infinity as opposed to F11 when focused at a moderate distance. Otherwise, diffraction would start to become very noticable. I think it's because the objects at infinity often appear very small and there aren't that many pixels covering them....so diffraction will often sneak in and make an otherwise sharp image appear slightly soft and fuzzy a little bit quicker than it would when focused on a larger object at a moderate distance. I wonder if this isn't the result of atmospheric effects and/or camera shake more than diffraction. In normal conditions, more distant objects are captured with lower contrast (and lower perceived sharpness) simply because there's more atmosphere to scatter and refract the light. And widening the aperture will give you a shorter exposure and less chance of noticeable camera movement (there's always some;)). Is the effect you observe independent of weather conditions? Does it make any difference if you use a rigid tripod? Link to post Share on other sites More sharing options...
farnz Posted May 3, 2009 Share #11 Posted May 3, 2009 The OP's problem is the images not lining up in the rangefinder's patch rather than sharpness at infinity as I understand it. Pete. Link to post Share on other sites More sharing options...
rob_x2004 Posted May 3, 2009 Share #12 Posted May 3, 2009 Louis there may be nothing wrong with your lens in itself. What is happening is your lens is reaching the correct infinty stop before the rangefinder reaches it. So the lens reaches its stop and the rangfinder fails to patch. That is fine at infinity. It may also be fine at near closest focus. In between these places, your lens has already passed through your point of focus before the rangefinder patches at that distance, so it will in effect back focus. That may or may not show up in your images. It is an easy fix for leica, they more than likely will slip the focus ring a tad, and you will be singing their praises. Remember that the depth of field behind is greater than depth of field in front so they have a bit of space to work in. However it is just as likely the cause of the problem lies in the linkages or the start point of the roller travel or any number of things in the assembly and set up of your camera body or bayonet and flanges. Apparently there is a massive jig for setting up some of the linkages and their neutral positions and from speaking to someone who knew the names of the individual techs that were good at setting it up, it struck me that there is plenty of room for someone not so experienced to get it wrong. It may also be that lately Leica might have been struggling with bayonet tolerances so everything gets pretty black hole very quickly. I have a perfectly functioning 75summicron that following a Solms service to an MP body failed to patch at infinity. Rather than sort out what they got pear shaped when putting the MP back together they slipped the focus ring on the lens and told me it was all in spec. Do I trust them? You dont know what else they got wrong so Im not exactly looking skywards in case pigs start shitting. Anyway you should be able to check that lens by throwing it on your mates cameras and see what is happening. But Id bet if you sent it Solmsward without your camera they would probably find it in spec. Welcome to the world of incompetence. Link to post Share on other sites More sharing options...
Gentleman Villain Posted May 3, 2009 Share #13 Posted May 3, 2009 I wonder if this isn't the result of atmospheric effects and/or camera shake more than diffraction. In normal conditions, more distant objects are captured with lower contrast (and lower perceived sharpness) simply because there's more atmosphere to scatter and refract the light. And widening the aperture will give you a shorter exposure and less chance of noticeable camera movement (there's always some;)). There's definitely truth to your statement! I can usually distinguish the difference between a low contrast sharp area of an image from diffraction. Diffraction kind of looks like peach fuzz. However, I often welcome slightly lower contrast...the atmosphere can add to the mood of the photograph (just like you said) Is the effect you observe independent of weather conditions? Does it make any difference if you use a rigid tripod? Yes definitely...and I always test my lenses using a tripod & cable release and always notice the same effect regardless of camera system. Photography is both an art & science so what is considered an acceptable level of diffraction for one photographer might be different for another photographer. I'm just relating my personal experience and taste. But I can DEFINITELY see the effects of diffraction. Some photographers can't really see it...they just know that it exists use formulas and calculations to try and avoid it. Link to post Share on other sites More sharing options...
biglouis Posted May 3, 2009 Author Share #14 Posted May 3, 2009 Thanks for the continuing comments. This is not camera shake, diffraction or anything other than the rangefinder patch not meeting at infinity. It does not happen with other lenses. Checked out the back focus on a test chart and it clearly does backfocus but by a tolerable amount, e.g. at f2.8 its widest setting I don't think this is a big issue. Indeed, today, photographing at the National Motorcycle Museum and using the lens wide open I could not detect back focus in my shots when I analysed them in CS3. I'm beginning to think I should continue to use the lens for a month or so and see if over time this is or is not a big issue. 'Stunsworth' has sent me the name of UK Leica tech who its sound like can easily CLA the lens if I want to. I probably will, just for my peace of mind but as Mark has pointed out I may be worrying unecessarily. Once again, thanks to all you knowledgeable forum members. Its advice like this that makes the forum a great place to hang out. LouisB Link to post Share on other sites More sharing options...
rob_x2004 Posted May 3, 2009 Share #15 Posted May 3, 2009 Checked out the back focus on a test chart and it clearly does backfocus but by a tolerable amount Is it definitely focusing back or is it the difference in the depths of field front and back make it appear so? In any case, there is probably room to slip the focus ring a fraction. Again, regardless of your other lenses its an even bet whether the issue is in your lens or body. Link to post Share on other sites More sharing options...
marknorton Posted May 4, 2009 Share #16 Posted May 4, 2009 Louis, how much a problem is there with the rangefinder path? When you set the lens to infinity and view a distant object, how big is the horizontal mis-alignment in relation to the width of the rangefinder patch? 50%, 20%, 10%, 5%? We're talking about fractions of a millimetre adjustment here and if you have a camera and other lenses which work, my advice is to leave well alone. I've come to the conclusion that the only real cure for focus misalignment is to give up pixel peeping. Link to post Share on other sites More sharing options...
wizard Posted May 4, 2009 Share #17 Posted May 4, 2009 ... my advice is to leave well alone. And I second that. What you are experiencing are normal tolerances. I have a bag full of Leica lenses, of which some are spot on, others show what you are describing and still others go even slightly beyond the infinity matching in the rangefinder. All of them are, however, tack sharp. So if you cannot detect any adverse effect on your results, don't bother to have the lens adjusted. Andy Link to post Share on other sites More sharing options...
jaapv Posted May 4, 2009 Share #18 Posted May 4, 2009 With rangefinder cameras, viewfinders are optically separated from the lenses. Besides 6-bit coding, if any, the only links are mechanical i.e. a focus cam in the lens barrel and a roller cam into the camera's body. Then diffraction cannot play any role in the alignment of the RF patch IMHO. There is quite a bit of screwdriver damage to that set screw... Link to post Share on other sites More sharing options...
marknorton Posted May 4, 2009 Share #19 Posted May 4, 2009 There is quite a bit of screwdriver damage to that set screw... And very good of LCT to remove his sensor and shutter for us to be able to see the back of the lens mount LOL... Link to post Share on other sites More sharing options...
lct Posted May 4, 2009 Share #20 Posted May 4, 2009 Just an old M4-2 mates. May look as worn out as its poor owner after 30+ years of work but it has no focusing problems at least. And no red nose either. :D Link to post Share on other sites More sharing options...
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