Very interesting answer from Leica on 35mm 1.4

[mjh]

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When a digi-slr focuses, it does so by contrast: so unless the lens is really out of whack the camera will compensate.

Yes, but that doesn’t really help in this case. The DSLR will focus with the aperture wide open and stop down only for the actual shot, so the focus shift will be just as severe. On the other hand, the AF knows about the type of lens and the aperture setting, so in principle it can compensate for this effect. A rangefinder camera does neither autofocus, nor does it know about the aperture setting, so it cannot apply any correction.

[tashley]

Trust me (even though I have a red AGA). The depth of field isn't moving back very much in those figures - you don't have to reduce the acceptable dof much as a percentage for it to move forwards instead.

If you do a calculation at each aperture for each distance, you will find the middle of the dof range moving away.

 

 

Not sure what you meant there but my point is that the actual point on which I focus moves into the OOF focus zone as I stop down.

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[tom0511]

This is an interesting thread as I'm looking to possibly unload a lens in order to finance the purchase of an M8. The 35 summ asph was the one I was thinking about though it's taken some real nice pics with M7 esp wide open (I also have 21 pre asph, 28 summ, 24, and 50 pre asph summ, 90 apo, and 135 elmar) esp at night.

......

Anyone have issues on other wide asph lenses? Who knows, maybe pre asph lenses will suddenly become sought after...

 

One saving grace of course is M8's 1/8000 shutter speed. At least easier to keep things down below f4.

 

I sent my 35lux and 28cron asph to Leica for focus calibration when I first received my rd1.

The focus accurancy has been improved and I would say these lenses are indeed usable now.

My 50/1.4asph has been atLeica lately, it now focuses (so far) perfect, and I can not detect problems with focus shift.

 

My Noctilux does show focus shift, even between f1.0 and f1.4 so that it focuses perfect at f1.4 but it looks that there is slight front focus at f1.0. MMmmmhhhhh!

 

75lux and 90Elmarit focus great.

 

My conclusion:

Best thing would be the posibility to check a certain lens on a certain camera, before buying it.

Otherwise check it afterwards and send it for Leica for calibration. Of course focus shift can not be eleminated by calibration, but if a lens is calibrated for coorect focus wide open, than the focus shift should not be such a big problem because of the increasing DOF when closing the aparture.

From reading the forum it looks like the 35/1.4asph and the Noctilux seem to be the most critical lenses these issues.

Regards, Tom

[ChrisC]

Tim - I was alarmed by your original post where you first reported mis-focus, but this current post alarms me even more. Clearly the problems with your 35 examples have rendered them unusable for your kind of photography, and yet [judging by photographs you have posted] they are often typically the type of photography that Leica associates itself with being where Leica photographers excel. Are we to re-evaluate whether these 'finest small format lenses in the world' can actually do their job; in close, in focus? I'm old school in this respect; a lens which second guesses my point of focus is unusable at cottage industry prices, and unforgivable at Leica prices. I completely understand your annoyance with what many herald as a 'legendary' lens.

 

.......... Another interesting paradox is if the focus drifts as we close down, how do we know if the softness is from that or the diffraction setting in? In fact how can we even document diffraction, if the target isn't in focus..........

 

I was thinking the same thing. No doubt we all more or less read the same reviews and recommendations about lenses, and I have often thought it curious how quickly some lens performances are said to deteriorate upon stopping down. The performance deterioration is usually attributed to lenses being corrected for stellar definition at wide apertures, should we now reconsider influential lens reviews unless we know that bracket focusing, upon closing down, was an integral part of the test procedure? Kudos for Sean in this respect; he states that he does bracket focus for his lens reviews.

 

I confess to being a little disturbed at what I might be buying into with [still on order] M8.

 

..................Chris

[innerimager]

Not sure what you meant there but my point is that the actual point on which I focus moves into the OOF focus zone as I stop down.

Tim- I've been puzzling about this exact point. Are you saying that, when you stop down, and then refocus each time, you get OOF images, or is it as in this quote. if you focus at say 1.4 and leave that focus, the image goes OOF as you stop down?

 

Clearly, if it's the latter, the lens is useable, so when you say it's not useable, I fear it's the former. So far, in my use, I have gotten acceptable sharpness with my 35 lux at all apertures, (well 1.4-11), but I always refocus whenever I bring the camera away and back to me eye as I assume a slight change in position will have occurred. best....Peter

[AlanG]

Tim,

I thought the original post reported a situation where the corners were sharp and the center was soft on photos shot at f4 at what I guess to be about 10 meters. What does this have to do with the focus shifting when stopping down? With the lens set at f4 and focused at 10 meters you should have DOF of 5 meters to infinity.

[leicar7]

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Yup, the PDF info on most of the M and R lenses predates the advent of the DMR and, certainly, the M8, and they are all calculated based on film and full format.

 

So perhaps using 100% blowup on digi image previews is tending toward unreasonable. I doubt that this problem is of a lesser order for the even smaller chips in the N and most C cameras.

 

So maybe one question becomes at what print size does the issue become apparent?

[Jamie Roberts]

Not sure what you meant there but my point is that the actual point on which I focus moves into the OOF focus zone as I stop down.

 

Leaving aside DOF issues and the different COC calculations (all of which are interesting), I can say categorically that my 35 1.4 ASPH does not do this; the object in focus remains the object in focus from 1.4 to f11 (I didn't even check f16, because of diffraction, and because I rarely, if ever, shoot stuff at that aperture).

 

Now I have to say the reason I can say this is that my M8 was backfocussing to begin with, wide open. So I spent half an hour with the adjustments described on the forum here, and this significantly improved close-focus wide-open sharpness.

 

I don't know if that has anything to do with it, but I didn't have a point of focus problem in any of those tests.

 

Now the one thing I didn't check very carefully was intermediate distance. Would that make a difference? I was really only checking close focus and infinity. But I did it at all apertures from 1.4 to 11....

 

(oh, and yes, I probably did "refocus" at every aperture. I honestly can't remember!)

[mwalker649]

I have a chance to buy a circa 1998 35 Lux...should I back out? I would be using it for inside low light people photography.

[billh]

Lens aberration arguments aside, this makes no sense to me. No one can use a camera if it does not focus accurately. My Canons 1D2, 1Ds2) focus accurately, regardless whether I am using a 300 f2.8 in AF mode, or the 180 f3.5 macro (always in manual mode) or the 180 Summicron, again focused manually. It would make me crazy if they shifted. Furthermore, everyone of us has used the Ms critically with film (slow fine grain film). if the plane of focus was an inch (25.4mm) or more behind the subject (usually eyes for me), there is no way in the world we would not notice it. lastly, what has been used for resolution tests in the past? Film, or course.

[jaapv]

I have a chance to buy a circa 1998 35 Lux...should I back out? I would be using it for inside low light people photography.

Basing buy decisions on internet discussions is generally not a good idea:rolleyes:

[cnguyen]

it's funny how we talk about front and back focus with our new leica M8. I don't remember there were any discussions on FF and BF on film M cameras. I think Leica should put a disclaimer that you will see a slight OOF when images are blown up to 100% like we all do on our computer screen nowadays. I think Canon did that with their products awhile back. FF and BF problems are common problems among DSLRs as well.

[billh]

........ FF and BF problems are common problems among DSLRs as well.

 

I don’t have those problems, nor does anyone I know have them. If someone is having these issues, there is something wrong with their camera. My M8 back focus problems are very significant, and vary with the different lenses. There is no way this is a result of “normal” lens aberration. if that were the case, the multi thousand dollar lenses would not be worth ten cents.

 

 

Here are some more examples -

 

http://homepage.mac.com/billh96007/.Pictures/180-300/Eyes%2C180%2C300.jpg

 

 

Leica 180,f2.8 Crop from 50 x 75 inch (127 x 191 CM) enlargement.

http://homepage.mac.com/billh96007/.Pictures/180-300/180%2Cleft%2C4837.jpg

 

 

Canon300,f4.0,left eye.From 50 x 75 inch (127 x 191 CM) enlargement

http://homepage.mac.com/billh96007/.Pictures/180-300/300%2Cf4%2Cleft%2C4869.jpg

 

http://homepage.mac.com/billh96007/.Pictures/Swimbest2006/Kona-diving,-1624.jpg

 

85mm@f1.2

http://homepage.mac.com/billh96007/.Pictures/Swimbest2006/Kona,-Loch-Ness-Bouv-6358.jpg

 

focus on the eye,

http://homepage.mac.com/billh96007/.Pictures/Swimbest2006/Niko,7844.jpg

 

APO 75 with film, f2.0,

http://homepage.mac.com/billh96007/.Pictures/APO75f2.0/14A,-APO75@f2.0.jpg

 

APO 75 with film, f4.0,

http://homepage.mac.com/billh96007/.Pictures/APO75f2.0/16A,-APO75@f4.0.jpg

 

Note there is no focus shift.

[bnelson]

Just got a 35 lux in from Tony at Popflash. First up now is testing this lens.

 

Thanks for this discussion. Without it I would not know what to check.

 

Bill

[tashley]

Tim- I've been puzzling about this exact point. Are you saying that, when you stop down, and then refocus each time, you get OOF images, or is it as in this quote. if you focus at say 1.4 and leave that focus, the image goes OOF as you stop down?

 

Clearly, if it's the latter, the lens is useable, so when you say it's not useable, I fear it's the former. So far, in my use, I have gotten acceptable sharpness with my 35 lux at all apertures, (well 1.4-11), but I always refocus whenever I bring the camera away and back to me eye as I assume a slight change in position will have occurred. best....Peter

 

 

Hi Peter,

 

My methodology is made clear in these shots. The setup remained the same (shot one) throughout with the camera mounted on a tripod and point of focus unchanged throughout, on the 20cm mark which was in line with 'Canon' on the box, which is what I focussed on using a 1.25 magnifier. The only changes between shots were stopping down one full stop at a time.

 

Shot 2 is F1.4 100% crop which shows good focus on 20cm mark and on 'Canon'. Shot 3 shows that by f4 'Canon' is significantly OOF and the ruler indicates that the actual point of focus has moved backwards by approximately 8 or 9 cm. Focus on 'Canon' is similar at 5.6 and then starts to improve at f8 as DOF increases but the POF moves back further. By F11 the word Canon is in about as good focus as it was at f1.4.

 

Shot one: (the test scene)

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Shot 2: (f1.4 crop)

 

Shot 3: (f4 crop)

 

So the tripod means that there's no need to refocus and indeed since the camera does not know the F stop it would be pointless to refocus.

 

Any thoughts?

 

Tim

 

ps Solms has answered my detailed query by suggesting I buy an Elmarit 28 f2.8 because 'is not affected by spherical aberration at all'.

[tashley]

Tim,

I thought the original post reported a situation where the corners were sharp and the center was soft on photos shot at f4 at what I guess to be about 10 meters. What does this have to do with the focus shifting when stopping down? With the lens set at f4 and focused at 10 meters you should have DOF of 5 meters to infinity.

 

 

Hi Alan,

 

That was what I first noticed in Venice on real world shots and I have not tested for the same phenomenon but according to Solms 'It is an image imperfection that occurs due to the increased refraction that occurs when rays strike the lens near its edge, in comparison with those that strike nearer the center.'

 

I've posted some shots now in this thread that show the backfocus test results I got, and I assume that the two phenomena are optically linked but give to different effects.

 

I think?

 

Best

 

Tim

[tashley]

Yup, the PDF info on most of the M and R lenses predates the advent of the DMR and, certainly, the M8, and they are all calculated based on film and full format.

 

So perhaps using 100% blowup on digi image previews is tending toward unreasonable. I doubt that this problem is of a lesser order for the even smaller chips in the N and most C cameras.

 

So maybe one question becomes at what print size does the issue become apparent?

 

I haven't done exhaustive tests on that but I can say that when I look at shots in Lightroom at Fit rather than Zoom size on a 20 inch monitor, I can quite often spot a shot taken on this lens - particularly as part of a series of shots where others were on my 50mm lux, which has impeccable manners - by it's general softness. That's roughly equivalent to a 10 by 8 inch print?

 

Tim

[tashley]

Leaving aside DOF issues and the different COC calculations (all of which are interesting), I can say categorically that my 35 1.4 ASPH does not do this; the object in focus remains the object in focus from 1.4 to f11 (I didn't even check f16, because of diffraction, and because I rarely, if ever, shoot stuff at that aperture).

 

Now I have to say the reason I can say this is that my M8 was backfocussing to begin with, wide open. So I spent half an hour with the adjustments described on the forum here, and this significantly improved close-focus wide-open sharpness.

 

I don't know if that has anything to do with it, but I didn't have a point of focus problem in any of those tests.

 

Now the one thing I didn't check very carefully was intermediate distance. Would that make a difference? I was really only checking close focus and infinity. But I did it at all apertures from 1.4 to 11....

 

(oh, and yes, I probably did "refocus" at every aperture. I honestly can't remember!)

 

Hi Jamie,

 

Please take a peek at the shots I've just posted above in this thread, they exemplify the issue. I did another less scientific one just before sending the second lens back, which was to use f4 outside in daylight, handheld, and with a 1.25 mag, and to focus exactly on a large, clear object about 25 feet way. When I chimped, it was clearly OOF but the highly textured object about 8 feet behind it was in perfect focus.

 

Tim

[sergiolov]

Hi Tim,

what I see in your test is very similar to the results I get from the 35 cron asph, with a small difference. My lens full open fronfocuses more (about 3 cm, as if the Canon was at the 23 cm mark) . This leaves more space to the change of the focus plane position stopping down, when this plane shifts back. I think this is the correct adjustement to compensate for the focus shift to mantain the subject in the focus area.

But this should be problematic only on short distance shots, as Alan G noted. At ten meters, the depth of the sharp area is more than ten times greater than what you get at 1 meter, so I think that the problem you see is of different nature, and that the generic and theorical reply you got from Solms is not applicable.

(Let us see these shots! Viareggio with the rain is challenging..)

Regards.

Sergio

 

(I read now your reply to Jaime. They must repair the lens...)

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[geoffreyg]

Under the law of "unintended consequences", I wonder if f.2 lenses might not be more worthwile than the Summiluxes. A bit more forgiving and less particular, especially with this issue which may be unsolveable.