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Old 11-25-2008   #41
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It's good to hear real use stories. I'm definitely getting one and will trade my Summicron against it. I just think the 'Cron has too much bite to it and would appreciate the extra stop or so.

In other peoples experience, how does the focus shift issue work at distances between 3-10 or so meters? Does the actual place of focus when at f1.5 move forward proportionally? That would be my only concern, that I would be in a low light situation focusing on something at 5m and actually get a result focused 12.5" in front of the subject and the natural DOF coverage at that distance not being enough to cover the margin or error.

Actually, as I write I'm checking the Online DoF calculator and at that distance there is some overlap in DoF to nearly cover focus shift as the DoF at f1.5 would be 0.85m and the focus shift would be about 30cm forward. This reminds me of Roger Hick's article and what the dude at Zeiss told him about the DoF coverage. Easy to get around, IMO.

Either way, I'm going to get one. I just think the images I see made with them have the look I'm missing since migrating to modern lenses. Can't wait to get my hands on one!
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Old 11-25-2008   #42
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Quote:
Originally Posted by TJV View Post
how does the focus shift issue work at distances between 3-10 or so meters? Does the actual place of focus when at f1.5 move forward proportionally? That would be my only concern, that I would be in a low light situation focusing on something at 5m and actually get a result focused 12.5" in front of the subject and the natural DOF coverage at that distance not being enough to cover the margin or error.
Have not noticed any, I always assumed that any focus shift was eaten up by DoF.

Hope you enjoy it, it's a great lens!
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Old 11-28-2008   #43
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After almost a year with the C Sonnar optimized for f/2.8, I am contemplating, with some regret, having Cosina adjust it for f/1.5 .
Overall, I still think the lens is best optimized at f/2.8 . However, since I usually carry this lens in a kit with other lenses that are slower, I end up turning to the C Sonnar precisely for its speed. And most often at MFD. Here the focus shift is pronounced. I have been trying to train myself to compensate. However, although my success rate has increased with practice, the results are still not reliable enough for me.

I'll probably regret the change in performance at f/2.8 - 4.0 once the lens is recalibrated by Cosina, but
everything is a compromise.
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Old 11-29-2008   #44
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It's great that the option to have the lens recalibrated is there, and for free! I can't imagine Leica ever offering such a service for free. It's interesting to note that the Noctilux shifts more in focus according to most tests I've seen.

I'm really looking forward to getting my Sonnar. I have to thank a friend who I met at work who will send one back for me from Singapore. I'm stressing what sort of film to run through it first, colour or BW!

Quote:
Originally Posted by noimmunity View Post
After almost a year with the C Sonnar optimized for f/2.8, I am contemplating, with some regret, having Cosina adjust it for f/1.5 .
Overall, I still think the lens is best optimized at f/2.8 . However, since I usually carry this lens in a kit with other lenses that are slower, I end up turning to the C Sonnar precisely for its speed. And most often at MFD. Here the focus shift is pronounced. I have been trying to train myself to compensate. However, although my success rate has increased with practice, the results are still not reliable enough for me.

I'll probably regret the change in performance at f/2.8 - 4.0 once the lens is recalibrated by Cosina, but
everything is a compromise.
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Old 11-30-2008   #45
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I've owned the ZM 50/1.5 C Sonnar optimized for f/2.8 and found it to be a good performer providing that the lens gives exactly correct rf focus with the camera body used. An easy way to tell would be to make sure the lens didn't cause the camera's rf patch to overshoot infinity coincidence at it's endpoint, even in the slightest amount. If it falls slightly short of perfect coincidence, this may be quite acceptable as well since this mitigates effective focus shift by inducing a little "backfocus" to offset the "frontfocus" effects of it's inherent focus shift.
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Old 11-30-2008   #46
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Quote:
Originally Posted by Dante_Stella View Post
Try this focusing technique with the Sonnar. At f/1.5, focus from near to far and stop at the farthest distance where the RF arguably lines up. At f/2 and smaller, focus the other way and stop at the nearest distance that the RF lines up. Your break point may be f/2.4 or f/2.8, but you can figure this out pretty quickly.
I wonder if someone can help me with this one.

I'm not understanding what Dante is telling us with this focusing technique. Can anyone explain it so that I cna understand. The problem is me - not Dante - but I'm just not getting what he's saying. Help.

Thanks.
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Old 11-30-2008   #47
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Huck, what Dante is saying is that it makes a difference as to whether you rotate the focus ring from nearest focus or from infinity due to play in the rangefinder mechanism on Leica Ms.

I confirmed this by marking the position of the lens focus ring when focusing on an object 3 metres away. When focussing from infinity to 3 metres the rangefinder lines up a bit further away than 3 metres on the focus scale of the lens. When focussing from nearest focus to 3 metres the rangefinder lines up a bit nearer than three metres markings on the lens.

You can use this way of focussing to make up for a bit of front or backfocus in the lens if you know its behaviour.

I hope this makes it clearer

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Old 12-01-2008   #48
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T - I opted to get a lens optimized for f1.5, because: 1) I don't want to have to adjust when I want to shoot wide open, and 2) if I stop down, the DOF will "hide" the focus shift anyway. As others have said, in the real world, I'm not sure that it matters one way or another.

Example - on the street, with a subject 10 feet away: at f1.5, DOF is about 1 foot, while at f2.8 DOF is about 2 feet. A lens optimized for f2.8, even with focus shift, would still capture the point of focus within its DOF if shot wide open at f1.5. However, since things are moving relatively fast on the street, I would typically stop down anyway and shoot at f5.6, which makes moot the question of optimizing at f1.5 or f2.8.

I'll post some when I get a chance.

Keith
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Old 12-01-2008   #49
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Sonnar is a very attractive choice. First here is mentioned "new" and "old" version and new was 1.5 calibrated. Was that new/old true for Zeiss manufacturing or something personal purchace? Did I know which one it is when buying brand new and Zeiss is manufacturing both still?
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Old 12-01-2008   #50
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Zeiss calibrate them to f2.8 out of the factory and for special requests adjust it to f1.5 for fee under warranty.
T

Quote:
Originally Posted by mirrored View Post
Sonnar is a very attractive choice. First here is mentioned "new" and "old" version and new was 1.5 calibrated. Was that new/old true for Zeiss manufacturing or something personal purchace? Did I know which one it is when buying brand new and Zeiss is manufacturing both still?
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Old 12-02-2008   #51
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i dont understand one thing - why zeiss dont make f2 version - i think that version would cover both mistakes on f1.5 and f2.8... i think it would make f1.5 acceptable and on the edge of DOF and also it wouldnt make big mistakes on smaller apertures...
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Old 12-02-2008   #52
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Quote:
Originally Posted by kxl View Post
T - I opted to get a lens optimized for f1.5, because: 1) I don't want to have to adjust when I want to shoot wide open, and 2) if I stop down, the DOF will "hide" the focus shift anyway. As others have said, in the real world, I'm not sure that it matters one way or another.

Example - on the street, with a subject 10 feet away: at f1.5, DOF is about 1 foot, while at f2.8 DOF is about 2 feet. A lens optimized for f2.8, even with focus shift, would still capture the point of focus within its DOF if shot wide open at f1.5. However, since things are moving relatively fast on the street, I would typically stop down anyway and shoot at f5.6, which makes moot the question of optimizing at f1.5 or f2.8.

I'll post some when I get a chance.

Keith
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
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Old 12-02-2008   #53
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Quote:
Originally Posted by TJV View Post
Zeiss calibrate them to f2.8 out of the factory and for special requests adjust it to f1.5 for fee under warranty.
T
The adjustment is free under warranty. Customer pays for shipping.

Quote:
Originally Posted by Huck Finn View Post
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
It's worth repeating, too, that the direction of the focus shift relative to the camera is different. On the f/2.8 optimized version shot at full aperture at MFD, the DOF falls well in front of the point of focus. On the f/1.5 version at f/2.8 and f/4, the DOF goes back starting from the point of focus. So with the latter, you at least have a reliable index in the VF of where the starting point of the DOF lies.

A word about focusing technique: for the f/2.8 version, it is often said that all you need to do is "focus on the ear" at MFD and full aperture. In practice, I found this is much harder than it sounds. It may sound elemental, but ears are not actually all that visible. Trying to focus on an ear in its natural habitat, i.e., covered in hair, especially in low light, is much harder. Noses and eyes, generally exposed, offer excellent targets for low light focusing.

(I did try and practice quite a bit with other techniques such as the unidirectional focus, the physical lean-in, the additional turn of the lens. But I couldn't get my results to be reliable at f/1.5 and MFD on an f/2.8 optimised lens. But that's just me. Other people will have better technique, Bravo!).
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Old 12-02-2008   #54
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Quote:
Originally Posted by Huck Finn View Post
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
Without knowing what the actual focus shift is at f/2.8 and f/4 at distances greater than the MFD, that's not possible to prove or disprove.

Example: presetting the focus to 10ft, @ f/1.5, DOF is 1 ft (9.5 ft to 10.5 ft); @ f/2.8, point of focus shifts back to 10ft + X, with DOF of 2 ft (1 ft in front and 2 ft behind); at f/4, focus shifts back to 10 + X + Y, with DOF of 3 ft (1.5 ft in front and 1.5 ft behind).

So, as long as X is less than 12 inches and X plus Y is less than 15 inches, DOF will be sufficient, the point of focus of 10 ft. will be within the DOF.
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Old 12-02-2008   #55
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Quote:
Originally Posted by Huck Finn View Post
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
Correction: I checked my notes & it is at f/5.6 that focus shift is a problem when the lens is optimized for f/1.5.

I also came across an interesting note from Dr. Hubert Nasse in a correspondence we had about the C-Sonnar. It reads as follows:

"As a rule of thumb, you may assume that up to f/5.6 the focus shift roughly corresponds to half of the total depth-of-field. In other words: in a lens in which the lens & the lens cam are adjusted for best focus at f/1.5, when the camera is focused with the rangefinder, the best focus of the stopped down lens will be at a distance which is not at the main index but at the corresponding DOF mark.

The shift is positive, so the best focus distance is larger than intended. This means that the distance at the left of the DOF mark has to be set to the main index to achieve best focus of the stopped lens. (As with all non-floating lenses , these effects get a bit stronger at close distance.)"


I hope that this is helpful.
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Old 12-03-2008   #56
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Wow Huck Finn is back, long time no see?
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Old 12-04-2008   #57
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Wow Huck Finn is back, long time no see?
Nice to hear from you, too. How are things "down under"?
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Old 12-06-2008   #58
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after a few months of messing with the C-Sonnar, optimised for f/2.8, i am finally giving in and having it re-calibrated by Zeiss Germany (they are great to deal with, btw).

i use this lens, more often than not, wide open on my R-D1 (which i believe, is less forgiving than a film camera). i shoot in very low light most of the time as the 75mm-equivalent (1.5 crop factor) makes the 50mm lens less than ideal for street.

i love the lens but have agree with noimmunity that focusing on the ears is easier said than done.... having to "lean in" also messes with your framing and i've just become altogether to obsessed with getting focus, making the lens less of a joy than it should be.

TJV asked for a real world example. here's one taken at minimum focusing distance and then leaning in (larger version here):
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Old 12-06-2008   #59
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also, i need to make a CD of images to show Zeiss where the focus shift occurs on my camera (they have an Epson, but says each camera is unique).

does anybody have suggestions on the best way to go about this?

thank you in advance!
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Old 12-06-2008   #60
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Hi cam. I sent my C Sonnar to Cosina yesterday.
If that's the way you are going about it I would just send the camera body with the lens. Especially since it is just over the Rhine, the turnaround should be very quick and no extra import duty.
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Old 12-06-2008   #61
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oh my!

i don't think i could last that long without my baby!

i go through major withdrawal if i've neglected to take it with me for a few hours. a week or two would leave me rabid!
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Old 12-06-2008   #62
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I understand. The RF is a kind of defining moment. If I weren't half way around the world, I'd loan you a Bessa T.
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Old 12-06-2008   #63
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time to buy a back up body perhaps?
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Old 12-06-2008   #64
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Quote:
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I understand. The RF is a kind of defining moment. If I weren't half way around the world, I'd loan you a Bessa T.
thank you for the offer i got it bad!


Quote:
Originally Posted by back alley View Post
time to buy a back up body perhaps?
it probably is, but i can't quite decide what that would be -- an M8.2 if i could afford it (though i still prefer the R-D1's handling) or getting a film camera....

money is the problem, obviously. and my lust for lenses. i have a chance to get a mint Thambar and recently fell in love with the 75mm Summilux. i am obsessed by both, probably, because i have yet to find a wide angle (the one i need) that floats my boat *and* is fast enough.
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Old 12-07-2008   #65
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There might be a focus shift visible too.
http://www.rangefinderforum.com/foru...0&postcount=17
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Old 06-11-2009   #66
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your test is very usefull, thank you!

Another thing is the thing with curvature of field.
As you focus on the eyes and then recompose the camera,
you get into another focus plane, because best focus point is not plane over the field, but slightly curved.
it would be interesting if this situation decreases or increases the focus shift symptom on the two different optimised lenses.

i hope you understand my words, as its not easy two right this stuff in "another" language! ;-)

peter
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Old 06-11-2009   #67
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If you focus wide open with the f2.8 version, and then recompose tilting the camera a bit forward, this should compensate the front focus of the lens, but you have to work out the correct distance to make it work well.
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Thank you all !!
Old 06-17-2009   #68
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Thank you all !!

Hi ppl,

Would like to thank all of you for your input.
Just completed an order for a silver ZI and also a silver 50mm f1,5 C Sonnar optimized for 2.8 !!!!

Can't wait to get my hands on them !!
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Old 07-14-2009   #69
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I tested the c sonnar at f1.5 f2 f2.8 in 0.9m
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File Type: jpg Scan-090705-0046.jpg (40.1 KB, 137 views)
File Type: jpg Scan-090705-0047.jpg (37.7 KB, 104 views)
File Type: jpg Scan-090705-0048.jpg (38.4 KB, 116 views)
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Got new Sonnar and it is not f1,5 optimised
Old 09-04-2009   #70
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Thumbs up Got new Sonnar and it is not f1,5 optimised

Thanks very much for the comparison and interesting discussion. I last week bought this lens (new) and it seems my sample is not optimised for f1,5. At f1,5 and 90cm distance I get front focus of about 1,5 cm, but at 5m distance front focus is already about 25 cm. I tested with both ZI and M6 bodies and get about the same results.

Serial number of my lens is 15602820. I'm not sure if that is old stock or new samples are not f1,5 optimised. Has anyone bought this lens recently and received f1,5 optimised version or this talk that new samples are f1,5 optimised from factory is just an urban legend based on "someone at B&H told me they are"?

Besides tests with focus target I have done some real world shots and most show front focus. When I focus on eyes then actual focus is on nose.

Thanks!

Ahto
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Old 09-04-2009   #71
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Thanks Mike, great tests. For my preferences, they both front focus too much. But I can see why folks like them, it's like automatic soft-focus on the subject, whichever lens you pick.
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Old 09-30-2009   #72
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Just one photo taken at the end or the roll, not yet developed. Some testing this weekend with a 1.5 optimized version. Interesting point of Dante Stella's on page 2 of this thread. My Celestron telescope manual recommends a similar technique of moving the motor drive from one direction only if possible for accurate alignment of the celestial drive, again because of play inherent in the mechanism. I still expect to have focus shift issues that will be noticeable at close distances at f2.8-5.6 based especially on these very helpful tests of Marek's, but I assume it will be easier to find a work around than it would have been for the shallower DOF at 1.5 with the 2.8 optimized version. I am hoping to do this by feel: focus and then just shift the lens focus closer by a few degrees of rotation. It will be very interesting to see if focussing from close out to the distance of the first RF alignment will be sufficient to compensate for the 3-4cm posterior focus shift in Marek's tests. We'll see....at moderate distances this may well work.
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The Sonnar design at fault?
Old 11-03-2009   #73
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Question The Sonnar design at fault?

After reading through this whole thread, I am still stuck with one question.

Is the focus shift inherent to the Sonnar lens design?

Why am I wondering about this? A number of reasons, combined:
  • The Zeiss quote states the design of the current C-Sonnar goes back to the 1930 design. The lens since then apparently has not shed its front focusing issue.
  • The Sonnar-clone Jupiter lenses all front focus at MFD.
  • In a post from LeicaTom on the wartime Sonnars I have read these lenses also front focus when not adjusted by Brian.
I love the Sonnar look, but am worried by the focus shift. All proposed solutions (re-collimating, leaning in, shifting focus ring, etc.) will not cut it consistently when shooting portraits, which I would use the lens for.

So, question: does anyone have any accurate data on the Canon 50mm f1.5 Sonnar and the Steinheil Quinon 50mm 2.0 Sonnar? In short, does any of these two lenses consistently focus correctly wide open from MFD to say, three meters distance? I'd like to focus eyes, not ears!
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Old 11-03-2009   #74
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i have never had a problem with this focus shift. i rarely focus at minimum distance but prefer to be at least 4 or more feet away from my subject.
check my flickr account for the 50 set.
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Old 11-03-2009   #75
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Quote:
Originally Posted by CLE-RF View Post
So, question: does anyone have any accurate data on the Canon 50mm f1.5 Sonnar and the Steinheil Quinon 50mm 2.0 Sonnar? In short, does any of these two lenses consistently focus correctly wide open from MFD to say, three meters distance? I'd like to focus eyes, not ears!
Try a Nikkor 50/1.4. Here it is wide open:




here at f2:




here at f2.8:




QA with those lenses was very good. If clean, you can expect it to behave like this. Plus it can be modified to 0.7m min. focus.

Roland.
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Old 11-03-2009   #76
Brian Sweeney
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>So, question: does anyone have any accurate data on the Canon 50mm f1.5 Sonnar and
>the Steinheil Quinon 50mm 2.0 Sonnar? In short, does any of these two lenses
>consistently focus correctly wide open from MFD to say, three meters distance? I'd like to
>focus eyes, not ears!

I optimized my Canon 50/1.5 for best focus at F1.5. My lens was spot-on at F2.8. My Nikkor is spot-on at F1.4. So I made the Canon focus perfectly at F1.5 by changing the main shim. It is a 51.6mm lens, designed to the Leica Spec. It is in best focus at F1.5 across the range. Stopping down to F4 covers any focus shift. My Nikkor is spot-on at F1.4 across the range as it is also designed to the Leica spec.

The J-3 and Zeiss Sonnars are designed to the Contax spec. The focal length is ~52.4mm. I set them for best focus wide-open and up-close. They maintain that best focus to about 5m. After that, I like top stop down a little.

Last edited by Brian Sweeney : 11-03-2009 at 14:42.
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Old 11-03-2009   #77
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Brian,

I read the other thread with your shots as well, before taking in all the wonderful info on this one.

I did not realise that my question was already answered in the first thread, the vast amount of info on Sonnars must have blinded me... Oops.

Roland, thanks for showing these shots, I find them very impressive! Pretty sure this is the lens I will be looking for to use as a main portrait lens.

From looking at your test shots, I'm positive the Nikkor will be spot on when shot wide open.
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Old 11-03-2009   #78
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Have no fear, Johan, this is the Nikkor very close:



Krosya and Naruto/Ashwin can show you similar photos ...

Cheers,

Roland.
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Old 12-19-2009   #79
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I just acquired a used ZM 50/1.5 C-Sonnar, optimized at f/2.8. I'm looking forward to seeing what I can do with it.

The seller was a professional photographer who takes far better photographs than I ever will who was selling off his film equipment because of the move to digital. He was kind enough to share his impressions of the lens, so I thought I would post them here for the benefit of anyone who is considering this lens:

Please note that I used the lens with a new Zeiss Ikon M body. I always used a hood (only to protect the lens) and I never used a filter.

The lens has 2 distinct personalities.

At apertures smaller than f/4 it is a very sharp lens. But it never gives photos with a clinical look. The contrast is well balanced in my opinion In fact it handles high contrast & sharp lighting extremely well. I never noticed any flare. The lens focuses reliably near the minimum focus distance. I typically used f/5.6-f/8 in bright conditions.

At apertures below f/4 the lens behaves very differently. The way it draws is unique & lovely. The bokeh is pleasant & subtle. The color rendition and black & white tonality is mellow. At f/1.5 the vignetting is not trivial, but as you stop down it's less noticeable. The vignetting is the C-Sonnar's only flaw.

At f/1.5 the lens gives clear well-defined photos, but they are not sharp. The term soft exaggerates the lack of sharpness; the softness wide open is unlike any other fast lens I've used. I really don't know how to describe this with words. I would think to myself:this isn't sharp, but it looks good.

By f/2, the lens' characteristics change. As you know there is a focus shift below f/2.8. In my experience unless you are near the minimum focus distance, the focus shift is more accurately described as a very asymmetrical depth of field. The 1/3 rule of thumb for DOF does not apply. The DOF extends in front of the focus point.

Now we all know focusing at small distances at f/1.5 using a rangifinder is problematic. The rangefinder alignment, how the focus cam mates to the lens, & just the smallest amount of body lean between the time the focus is set and the shutter is pushed can lead to inconsistent results.

When I used the lens wide open at distances shorter than 8 feet, my success rate was good . . . but certainly not perfect. I was never more frustrated focusing this lens than I was with any other fast lens I've owned.

After reading dozens of posts about this lens over the years, I have come to believe that some Leica M focus cams do not mate well with this lens & the focus error at relatively close distances can be large. I don't know how else to explain the difference between my experience with the C-Sonnar and those who ended up being frustrated with the lens.

My advice for subjects 6 feet and further, shooting wide open in low light situations is straightforward: I simply focused a bit behind the intended focus point as the subject distance approached 6 feet. The further away the subject was, the less I even thought about focusing.

For subjects closer than 6 feet, I would bracket focusing behind the intended focus point.

The bokeh at f/2-f/4 is very pleasant to my eye. Never hesitate to use the lens in bright' harsh light. I liked how the lens worked with Kodak Porta film.


I hope that any readers here find this description of the characteristics of the ZM 50/1.5 C-Sonnar lens as helpful as I did.
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Old 12-19-2009   #80
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thanks, huck. practical and useful info which i appreciate.
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