Kevcaster
Well-known
Hi All
I recently bought an F1.5 Sonnar uncoated pre-war from another place. The focus appears to be off or the lens elements are suspect as I am unable to coax a sharp image from this lens.
Here are four pictures, one full frame with a 1961 F2.0 Coated Carl Zeiss Sonnar at F8.00, one 20% crop same lens and two 20% crops with the F1.5 Sonnar.
One with the F1.5 Sonnar at F1.5, one at F8.0. All on the same roll of FP4, Contax lla body, film developed in Rodinal 1:50 14 mins. The extra picture is the full frame taken with the 1961 Sonnar.
Sonnar F1,5 @F1.5crop by Kevin, on Flickr
Sonnar F1,5 @F8,0crop by Kevin, on Flickr
Coated Sonnar F2.0 @F8.0crop by Kevin, on Flickr
Full frame - Coated Sonnar F2.0 @F5.6 by Kevin, on Flickr
I have disassembled the lens cleaned the elements, cleaned the aperture blades and re-assembled. There is signs of tampering, the front bezel screws are missing and the holes plugged with brass rod, the elements are in pristine condition. There is a 2mm optical blemish dead centre in the rear element, looks like an internal bubble, quite large perfectly circular. There are four focus adjustment shims: one aluminium, two brass and a very thin copper shim - too many for Zeiss? I cannot imagine these are all original, what do you think?
What should I expect from this lens, some say it is the best of the Sonnars but this under performs even compared to the pre-war Tessar.
Any advice gratefully received
Best to all
Kevin
I recently bought an F1.5 Sonnar uncoated pre-war from another place. The focus appears to be off or the lens elements are suspect as I am unable to coax a sharp image from this lens.
Here are four pictures, one full frame with a 1961 F2.0 Coated Carl Zeiss Sonnar at F8.00, one 20% crop same lens and two 20% crops with the F1.5 Sonnar.
One with the F1.5 Sonnar at F1.5, one at F8.0. All on the same roll of FP4, Contax lla body, film developed in Rodinal 1:50 14 mins. The extra picture is the full frame taken with the 1961 Sonnar.
Sonnar F1,5 @F1.5crop by Kevin, on Flickr
Sonnar F1,5 @F8,0crop by Kevin, on Flickr
Coated Sonnar F2.0 @F8.0crop by Kevin, on Flickr
Full frame - Coated Sonnar F2.0 @F5.6 by Kevin, on Flickr
I have disassembled the lens cleaned the elements, cleaned the aperture blades and re-assembled. There is signs of tampering, the front bezel screws are missing and the holes plugged with brass rod, the elements are in pristine condition. There is a 2mm optical blemish dead centre in the rear element, looks like an internal bubble, quite large perfectly circular. There are four focus adjustment shims: one aluminium, two brass and a very thin copper shim - too many for Zeiss? I cannot imagine these are all original, what do you think?
What should I expect from this lens, some say it is the best of the Sonnars but this under performs even compared to the pre-war Tessar.
Any advice gratefully received
Best to all
Kevin
Mudman
Well-known
It sounds like too many shims. I'd try taking out one of the larger ones, re-assemble and then put some scotch tape across the film gate in the camera and focus off of that to see if you've now gotten better focus (doesn't look like it could get much worse!). This is of course assuming that your IIa or II is working normally with your other lenses, which it looks like it is.
Cheers,
Eric
Cheers,
Eric
I agree with Mudman. I'd say there's too many shims in there, causing the lens to front focus.
The scotch tape on the film gate trick is a good idea, but I'd test with film to be sure. So I suggest you load a roll of film and try shooting a target about 10 meters away at say f1.5, f2.0, and f2.8 with objects closer in the foreground and further off in the background included in the frame (preferably as far back as infinity - a fence at an angle would be ideal) so you can see where the actual point of focus is on the negative. With the camera on a tripod for framing consistency, take a series of shots with each shim combination and note which shim combination you used. Then develop and scan your film and check which shim combination gave the best focus.
If the actual point of focus falls behind what you focused on, your combined shim thickness is too thin. If the actual point of focus falls in front of what you focused on, your combined shim thickness is too thick. With a bit of trial and error testing, you should be able to hone in on the correct shim combination for your needs.
Using a loupe and ground glass over the film rails of the camera, plus a locking cable release to keep the shutter open, should speed the process of selecting shims up somewhat. Proof positive is of course sharp images on film, but you should be able to get the lens well in the ballpark this way. For greatly increased precision of your adjustments, the only additional things you need are a simple piece of plain glass the approximate dimensions of the pressure plate, a piece of unexposed, and developed, black and white film, and a trustworthy SLR fitted with a long focus lens to act as a collimator. In this forum post I discuss how these items are used to inspect and set the focus adjustment of a Rollei twin lens, however the procedure works equally well when used for a rangefinder (or another SLR).
Cheers,
Brett
Cheers,
Brett
Kevcaster
Well-known
Many thanks to all of you, very valuable information. I did ALL of the above and finally collimated the lens using Mike Elek's guide.
Here are samples after the first try, all pictures are 20% crops of the full negatives:
Sonnar after collimation F5.6crop by Kevin, on Flickr
Sonnar after collimation F1.5closeupBcrop by Kevin, on Flickr
As you see in the second picture the focus is still in front of the subject by around 100mm meaning that the optical unit has to move back in the mount. I tried again using a Rollei screen as the ground glass and found this more definite than the piece of Mamiya screen I had been using. And so I reduced the shims inside the lens and as the second test shows by a little too much.
Forgive the quality, I underexposed the negs by mistake, here are samples: The rangefinder was focused on the knot hole on the edge of the front vertical plank. The first at F1.5 clearly shows the actual point of focus is now behind the knothole not in front. The second at F11.00 (the minimum on this pre-war lens) is more forgiving with it's greater depth of field but still not right.
Sonnar after collimation 2closeup F1.5 copycrop by Kevin, on Flickr
Sonnar after collimation 2closeup F11.0 copycrop by Kevin, on Flickr
The collimating collar inside the lens has been fixed in place with a rod and so cannot be moved, is this standard? If it is then the only option is to continue with shims and I ran out of time for a third test.
This lens has been properly messed about with and I am currently underwhelmed with the performance of this F1.5 Sonnar which seems to be at odds with the general opinion, I can't help thinking that there are further issues with it.
Thanks again for all the advice, any further insights you may have please share them.
Kevin
Here are samples after the first try, all pictures are 20% crops of the full negatives:
Sonnar after collimation F5.6crop by Kevin, on Flickr
Sonnar after collimation F1.5closeupBcrop by Kevin, on Flickr
As you see in the second picture the focus is still in front of the subject by around 100mm meaning that the optical unit has to move back in the mount. I tried again using a Rollei screen as the ground glass and found this more definite than the piece of Mamiya screen I had been using. And so I reduced the shims inside the lens and as the second test shows by a little too much.
Forgive the quality, I underexposed the negs by mistake, here are samples: The rangefinder was focused on the knot hole on the edge of the front vertical plank. The first at F1.5 clearly shows the actual point of focus is now behind the knothole not in front. The second at F11.00 (the minimum on this pre-war lens) is more forgiving with it's greater depth of field but still not right.
Sonnar after collimation 2closeup F1.5 copycrop by Kevin, on Flickr
Sonnar after collimation 2closeup F11.0 copycrop by Kevin, on Flickr
The collimating collar inside the lens has been fixed in place with a rod and so cannot be moved, is this standard? If it is then the only option is to continue with shims and I ran out of time for a third test.
This lens has been properly messed about with and I am currently underwhelmed with the performance of this F1.5 Sonnar which seems to be at odds with the general opinion, I can't help thinking that there are further issues with it.
Thanks again for all the advice, any further insights you may have please share them.
Kevin
Hi,
despite your time constraints you are making progress as the images are still greatly improved. Yes, I agree with the lens back focusing a bit it looks like perhaps one shim needs to go back in, or perhaps another shim of intermediate size. I am assuming that the rangefinder itself gives a good, crisp image when set to infinity. You are probably aware of this but it always bears repeating, that the exercise is really one of matching the rangefinder to the lens(es), not of matching the lens to the RF. If a lens is adjusted onto the camera body so that, when set to its infinity stop, a crisp image of a distant target is brought into focus, and, on checking at close range to a measured distance the lens indeed is focused at that distance--then you can be fairly happy about the primary film focus. If this does not translate into sharp images on film with the camera as focused with the rangefinder, then the required action will usually be calibrating the rangefinder until it agrees with the film plane.
It's likely that the lens itself requires further fine tuning given its issues you have previously demonstrated. But it's as well to bear the above in mind, because it is also possible to have focusing issues even with a lens that has perfect focus register with its camera body, if the rangefinder itself is out. For this reason I would recommend including an infinity shot or two in the next round of images as well as some close shots.
If further adjustments are needed (and it seems they are), I would concentrate on trying to collimate the lens infinity focus as well as you can, because (in theory) if you can get this bang on, the remainder of the distance scale should then fall nicely into place. Note that I said in theory. Depth of field will cover any slight calibration errors much better at or near infinity, than at minimum distance. So, if you are certain the infinity setting is excellent, and that the rangefinder is tracking perfectly with the lens, but, you still cannot get your focus bang on at close range, at that point, you may have to compromise absolute infinity accuracy for better results at close range, where any deviations will by far be most evident.
I do mention it in the linked post I referred to (regarding the Rollei focus adjustment) but, for the sake of clarity, for best collimation results you should be fitting a lens with a focal length at least double that of the one being adjusted: Ie. for the Sonnar you want at least a 100mm lens on the SLR you are examining its focus with. This increases the magnification of the focus target at the Contax film gate which improves accuracy, and if you have a suitable lens, by all means, try around 200mm for an even more precise view. If you can shim the Sonnar bang on to infinity, using the above steps, its accuracy at close range should be very close, (assuming the lens in question is a decent performer, something you have expressed some reservations about).
The only other possible way I can personally think of dealing with the dilemma of distant focus v close focus incompatibility, is if the particular rangefinder design in question facilitates separate adjustment of close focus from the master infinity adjustment. I've not owned one, but I understand certain Leica models can have a primary and tertiary adjustment system. And the Contax II rangefinder can, I believe, (from reading this information at the Kiev Survival Site) be fine tuned across various distances. The IIa I do not know as much about, but perhaps some of our owner/repairers can provide more information about them? Before trying this, you would definitely want to assess the rangefinder accuracy with any other lenses you would like to use on the camera, as it would be frustrating in the extreme to dial one in well, only to find that other lenses are subsequently off at close range, or elsewhere. Of course, if you only intend to fit one lens, you can optimise camera and body for this, but in any event, I would suggest leaving the rangefinder well alone (if its infinity image is good), until such time as you are quite sure that the lens itself is working well, and that its focus calibration is as good as it can possibly be, and then, consider re-setting the RF only as a last resort.
Hopefully the above assists. It's in the nature of general principles of adjustment, not specific to the Contax or the f/1.5 Sonnar which as I understand it manifests some focus shift at various apertures (and which is something you may want to take into account in terms of your preferred f stop, when making any adjustments).
This is all quite topical for me. I acquired a Contax II last month, and just this week purchased a 50mm f/1.5 myself to go on it (but a later Zeiss Opton Oberkochen version). So your experiences trying to remedy your pre-war example are both interesting and informative.
Cheers,
Brett
despite your time constraints you are making progress as the images are still greatly improved. Yes, I agree with the lens back focusing a bit it looks like perhaps one shim needs to go back in, or perhaps another shim of intermediate size. I am assuming that the rangefinder itself gives a good, crisp image when set to infinity. You are probably aware of this but it always bears repeating, that the exercise is really one of matching the rangefinder to the lens(es), not of matching the lens to the RF. If a lens is adjusted onto the camera body so that, when set to its infinity stop, a crisp image of a distant target is brought into focus, and, on checking at close range to a measured distance the lens indeed is focused at that distance--then you can be fairly happy about the primary film focus. If this does not translate into sharp images on film with the camera as focused with the rangefinder, then the required action will usually be calibrating the rangefinder until it agrees with the film plane.
It's likely that the lens itself requires further fine tuning given its issues you have previously demonstrated. But it's as well to bear the above in mind, because it is also possible to have focusing issues even with a lens that has perfect focus register with its camera body, if the rangefinder itself is out. For this reason I would recommend including an infinity shot or two in the next round of images as well as some close shots.
If further adjustments are needed (and it seems they are), I would concentrate on trying to collimate the lens infinity focus as well as you can, because (in theory) if you can get this bang on, the remainder of the distance scale should then fall nicely into place. Note that I said in theory. Depth of field will cover any slight calibration errors much better at or near infinity, than at minimum distance. So, if you are certain the infinity setting is excellent, and that the rangefinder is tracking perfectly with the lens, but, you still cannot get your focus bang on at close range, at that point, you may have to compromise absolute infinity accuracy for better results at close range, where any deviations will by far be most evident.
I do mention it in the linked post I referred to (regarding the Rollei focus adjustment) but, for the sake of clarity, for best collimation results you should be fitting a lens with a focal length at least double that of the one being adjusted: Ie. for the Sonnar you want at least a 100mm lens on the SLR you are examining its focus with. This increases the magnification of the focus target at the Contax film gate which improves accuracy, and if you have a suitable lens, by all means, try around 200mm for an even more precise view. If you can shim the Sonnar bang on to infinity, using the above steps, its accuracy at close range should be very close, (assuming the lens in question is a decent performer, something you have expressed some reservations about).
The only other possible way I can personally think of dealing with the dilemma of distant focus v close focus incompatibility, is if the particular rangefinder design in question facilitates separate adjustment of close focus from the master infinity adjustment. I've not owned one, but I understand certain Leica models can have a primary and tertiary adjustment system. And the Contax II rangefinder can, I believe, (from reading this information at the Kiev Survival Site) be fine tuned across various distances. The IIa I do not know as much about, but perhaps some of our owner/repairers can provide more information about them? Before trying this, you would definitely want to assess the rangefinder accuracy with any other lenses you would like to use on the camera, as it would be frustrating in the extreme to dial one in well, only to find that other lenses are subsequently off at close range, or elsewhere. Of course, if you only intend to fit one lens, you can optimise camera and body for this, but in any event, I would suggest leaving the rangefinder well alone (if its infinity image is good), until such time as you are quite sure that the lens itself is working well, and that its focus calibration is as good as it can possibly be, and then, consider re-setting the RF only as a last resort.
Hopefully the above assists. It's in the nature of general principles of adjustment, not specific to the Contax or the f/1.5 Sonnar which as I understand it manifests some focus shift at various apertures (and which is something you may want to take into account in terms of your preferred f stop, when making any adjustments).
This is all quite topical for me. I acquired a Contax II last month, and just this week purchased a 50mm f/1.5 myself to go on it (but a later Zeiss Opton Oberkochen version). So your experiences trying to remedy your pre-war example are both interesting and informative.
Cheers,
Brett
zeissguy
Member
Just a thought. If you have a micrometer, I recommend that you measure the thickness of the shims. That may give you a better idea about which shims should and should not be there.
Perhaps the Sonnar you bought was shimmed to work well on a Nikon rangefinder. If that was the case, then the thickness of the shims to remove so that it focusses properly on a Contax would be 0.31mm.
Perhaps the Sonnar you bought was shimmed to work well on a Nikon rangefinder. If that was the case, then the thickness of the shims to remove so that it focusses properly on a Contax would be 0.31mm.
That makes a lot of sense, excellent suggestions, both.
Measuring the shims with a micrometer is an excellent idea.
The OP's lens may indeed have been shimmed to focus accurately on a Nikon RF body at close distances. However, despite what Henry Scherer erroneously writes on his website, it is not possible to shim a Nikon lens for Contax or visa versa just by adding or removing a 0.31mm shim.
In their standard non-messed-about-with state, all Nikon RF lenses focus correctly on Contax bodies and all Contax lenses focus correctly on Nikon RF bodies at infinity (this is a key point). That is because the register (flange to film plane distance) is the same for both systems.
A focus error occurs at close distances between systems because the Contax mount is designed to rotate slightly more than the Nikon mount to reach the same minimum focus distance of 0.9 meters. I don't remember the exact figures but I think the Contax mount rotates about 280 degrees vs 270 degrees for the Nikon mount.
Shimming cannot fix that. All shimming can do is change the distance at which the focus error occurs (i.e. the lens can be shimmed so that focus at 1 meter is accurate at the expense of poor infinity focus).
Great post, thanks. I did not know that. Simply put, then, you're saying Contax v Nikon are not linear to each other from infinity to close? As I'm now a Contax owner, this is the sort of stuff I want to learn more about. Jupiters and so on would go with Contax not Nikon, yes?
Cheers,
Brett
Exactly. Here's a chart taken from the Voigtlander Bessa R2C/S manual. It shows, based on a circle of confusion of 33um, whether or not the image will be in focus at a specific aperture and distance for 50mm and 85mm lenses when a Nikon spec lens is used on a Contax body or visa versa. An O indicates the image will be in focus and an X indicates the image will not be in focus. DOF covers the focus error with 35mm lenses and wider. That's why Cosina designates their 35mm and wider S-mount lenses as SC and their 50mm and 85mm S-mount lenses as S (no C), even though all their lenses are actually S-mount.
Yep.
zeissguy
Member
Ok. I just did a lot of reading on this issue. I don't have the links handy right now. But Dante's site and Camera Quest's site were particularly helpful.
It appears that Nikon chose to use the same nominal focal length as Leica. Apparently, that focal length is something like 51.6mm for a "50mm" lens. Conversely, Contax went with a nominal focal length of something like 52.4mm for their "50mm" lens.
It appears that Nikon chose to use the same nominal focal length as Leica. Apparently, that focal length is something like 51.6mm for a "50mm" lens. Conversely, Contax went with a nominal focal length of something like 52.4mm for their "50mm" lens.
Kevcaster
Well-known
Yes good suggestion and would be consistent with my findings so far, in fact all good information.
I am working my way through this to discover what might be optimum. The front bezel is fixed a little further back than it should be so that may be an indication of the intent of the previous user (not the owner, it came from an online dealer who has credited me and told me "keep it"). This in itself presents the problem of the aperture lugs fouling the bezel when the shims are removed and this appears to be the optimum setting, so i may be getting the file out shortly. The additional result of removing the shims allows the original lock screw indent on the lens rear to match with the lock screw on the barrel. This also points to the idea of 'no shims'.
Thanks for all the help, this forum has never failed to get me through a knotty Contax problem!
Best
Kevin
Kevcaster
Well-known
Something strange going on here, I cannot get this lens to focus across a wide range of distances, I have tried setting it up for optimum focus at F1,5 and at F5.6 and neither produces a decent negative at varying focus points, I'm returning it in it's original state to the seller as I don't want an item I cannot use.
Thanks again for all the input, it has been interesting learning about all these methods and the results.
Kevin
Thanks again for all the input, it has been interesting learning about all these methods and the results.
Kevin
Whilst doing some general Contax research today I found a post by Brian Sweeney about the details of the Zeiss v Nikon Contax mount differences. He quotes 260 degrees of rotation of the Nikon RF helical from infinity to three feet, as opposed to 270 degrees for the Contax. He also talked of shimming a Nikon helical until a f/1.5 Sonnar focused sharply at 8 feet, making it usable on the Nikon by splitting the difference between the two mounts down the middle, basically. Fascinating stuff. For those of you who are members of the ZICG list on Yahoo the link to the original discussion is below. FYI
Cheers,
Brett
https://groups.yahoo.com/neo/groups/ZICG/conversations/topics/10752
Cheers,
Brett
https://groups.yahoo.com/neo/groups/ZICG/conversations/topics/10752
Highway 61
Revisited
I once bought a prewar Carl Zeiss Jena Sonnar 5cm f/1.5, uncoated (Contax mount), which was in truly mint condition and I'm 100% positive that it had never ever been taken apart. I had to clean it because the aperture blades were oily and sticky, so I routinely checked the lens collimation upon cleaning.
Surprise ! It was completely off at infinity. I carefully recollimated it with no major difficulties thanks to the "indoors infinity" method. At the end of the day once properly collimated the aperture ring didn't match its original indexes any longer (pretty logical) so I had to slightly drill the lens barrel underneath so that the aperture ring set screws could be fitted again.
This could be done quite easily and I still have this lens, it now performs very well at all distances and all apertures.
This doesn't seem to be fairly uncommon for lenses made in 1939 and later at the Jena plant. This was the war already and the QC had become a bit erratic.
Yours seem to suffer from a very different problem, though...
Surprise ! It was completely off at infinity. I carefully recollimated it with no major difficulties thanks to the "indoors infinity" method. At the end of the day once properly collimated the aperture ring didn't match its original indexes any longer (pretty logical) so I had to slightly drill the lens barrel underneath so that the aperture ring set screws could be fitted again.
This could be done quite easily and I still have this lens, it now performs very well at all distances and all apertures.
This doesn't seem to be fairly uncommon for lenses made in 1939 and later at the Jena plant. This was the war already and the QC had become a bit erratic.
Yours seem to suffer from a very different problem, though...
Kevcaster
Well-known
I returned the lens and bought another with a few known issues, some dust, bubbles, and cleaning scuffs - no scratches. It is a late 50's Carl Zeiss F1.5 and it too has some focus anomalies. It is perfect at infinity focus at F2.8 but has some shift at F2 and f1.5. For now I will simply use it and adjust my focus as needed (if I can, it appears to be about 120mm at 1.0 metre distance).
It seems to me that an F1.5 lens is likely to be most useful at closer distances, say in a restaurant, low light portraits and so on and wonder why Zeiss chose to optimise at F2.8? if there is logic I would like to understand that.
Highway 61
Revisited
Well, I never understood nuffin' to those Sonnar focus shift problems and discussions about whether the lens should be optimized for f/1.5 or f/2.8 so I can't help you the least bit...
When I collimated my defective CZJ Sonnar 50/1.5 I managed to see a sharp target at f/1.5 while doing the indoors infinity test. Since, the lens has performed well at all distances and all apertures (according to what I can see on the pics).
mcfingon
Western Australia
Kevcaster, the logic of the f2.8 optimization was that there is not as much focus shift after f2.8 on a f1.5 Sonnar, and it could be covered by increasing depth of field. RF accuracy would be high in the f2.8-f16 range. If you optimize for f1.5 as it was on my ZM 50/1.5 C Sonnar, there is a huge amount of focus shift away from you as you stop down. So, only f1.5 and possibly f2 are accurate on a newer ZM. You have to compensate for the rest by focusing closer.
If the focus shifts away from you as you stop down, won't focusing closer only exacerbate any discrepancy?