Help- another M8 focus question

[tom0511]

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I would be glad if you experienced guys could tell me if you think my M8 is focusing fine or if I should send it in.

The facts:

my TE, 75/1.4,90/2.8, 90/macro, wide angels (21-24-24) all focus perfect/spot on on my M8.

 

my 50/1.4asph backfocused on my M8, I sent it in, it is now very close toperfect with a very very slight backfocus (which is so small that its really fine)

 

my 35/1.4asph does front focus, and even after sending it to Leica for calibration it slightly frontfocuses at f1.4.

 

a Zeiss 50/1.5 which frontfocused and which I sent to Zeiss for calibrating it for f1.5 still clearly frontfocuses on my M8.

 

my Noctilux did frontfocus on my M8 at f1 and slightly at f1.4 but not at f2 and higher (caused by focus-shift). Its now atLeica for calibration because Iwould like it to focus precisly at f1.0

 

On one side I think my M8 is fine, because my 50/1.4, 75/1.4 and 90/2.8, 90macro and TE focus nearly perfect.

On the other side I am surprized to send in 2 lenses (35/1.4asph and 50/1.5) for calibration and they still show front focus.

 

Now I have 4 choices:

1) forget about the 35/1.4 and 50/1.5Zeiss, sell them and just use my other lenses (I am not using 35mm much anyways, more often 28 and 50)

 

2) send in my M8 and let them check it (with the risk that they change something and maybe my other lenses (50asph,75,90) dont focus that good any more)

 

3) send the lenses which dont work that great in a second time

 

4) (I am not really serious): buy a second M8 and see what happens on that camera.

 

Thanks a lot for any suggestions, Tom

[Laki]

i have been been told from the leica cs to send in the m8 and the lenses together and so i did that yesterday. they told me they need both together and also upgrade the m8 always to the newest version (electronically).

[carstenw]

Tom, have you tried the 2mm Allen key? It sounds overall like these are mostly minor problems which might be fixed by a small tweak to the wheel, to correct for a slight front-focus. If you lose infinity focus at that point, then the camera needs to go in. The rangefinder does lose adjustment slowly over time, so I think it is well worth learning to tune the wheel.

[marknorton]

Because it's impossible to tell whether it's the camera or lenses which are at fault, a kind of majority voting system applies. You have a number of lenses which are working correctly, so it's likely the camera is correctly aligned.

 

Because the focus shifts back when you stop down on the 35/1.4, it may be they now adjust it for slight front focus at f1.4 in an attempt to balance the focussing error over the aperture range f1.4 - (say) f4. After that, the increasing depth of field masks any focussing shift.

 

I do think the 35/1.4 is a problem lens and therefore avoid using it in the aperture range f2 - f4 when I'm shooting close up. Whether such circuvention should be required for a lens in this price range is another discussion.

[tom0511]

Carsten,

I havent tried the Allan key.

I am kind of afraid that after all I might end up in a way that my 50asph,75,90 wont focus good anymore if I change anything at the camera.

 

Mark- actually for the price of the 35/1.4asph I do not find it appropriate to accept slight out of focus.

 

Thanks for the answers so far. I wonder what would happen if I send my M8 + my more than 10 lenses to Leica? Probably they send me a bill in the value of a seconnd M8 body.

 

cheers, Tom

[marknorton]

Thomas, when you say the 35/1.5 front focusses slightly, how "slight" is "slightly"? If you are focussing at 1m, how far is it out? It may be your expectation is exceeding Leica's ability to adjust it.

 

The problems, or should I say characteristics of this lens are covered in the latest issue of the LFI.

[tom0511]

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Thomas, when you say the 35/1.5 front focusses slightly, how "slight" is "slightly"? If you are focussing at 1m, how far is it out? It may be your expectation is exceeding Leica's ability to adjust it.

 

The problems, or should I say characteristics of this lens are covered in the latest issue of the LFI.

 

Mark, at a distance of 1m I would say maybe 2-3cm. If I focus on a coin, the coin would be not sharp, but slightly before the coin

[ho_co]

Thomas--

Is this hypothetical coin shot when the lens is wide open? Erwin Puts says all Leica lenses should be exactly matched to rangefinder focus when at full aperture. 2-3 cm sounds like a big error if wide open.

 

But as Mark said, the 35/1.4 was designed with a carefully tuned set of compromises--see the article pp 42ff in LFI 6/2007.

 

It sounds to me as if when you sent it to Leica they may have adjusted it to front-focus slightly to try to mask the focus shift as you stop the lens down.

 

Good luck.

 

--HC

[Dan States]

High speed lenses are going to have some degree of focus shift. The Zeiss 50 1.5 is a "special" case because the shift is far behond the normal depth of field at the two wides apertures. If it doesn't front focus at 1.5 it will back focus at 2.8-16...take your pick. I returned my Sonnar(s) because, silly me, I wanted a wide aperture lens that I could focus at wide aperture.

 

The crop factor and the very high resolution of the M8 sensor, plus the fact that you can blow up your shots in about 15 seconds to mega size means many of the great high speed lens designs that were cherries for film are now pits on digital.

 

In the case of the 35 f1.4 you may want to ask yourself what size prints you will be making and wether the shift is actually visible on PRINT...not just on screen.

 

Best wishes

Dan

[Guest guy_mancuso]

Well this is interesting and since the long stuff is dead on than your M8 is dead on so forget the M8 being out the tightest tolerence for the 90 and 75 occur and exactly what leica will do is adjust the M8 to that so the issue is the 35 1.4 which frankly is a issue in my opinion.

My case i had everything set for a calibrated to the wall M8 everything was good except the 50 lux and 135 which i sent in for shimming there dead on but the 35 mm lux i just gave up on and sold it and bought the 35 cron which i actually like better. Get the 35 lux fixed save the rest

[marknorton]

Mark, at a distance of 1m I would say maybe 2-3cm. If I focus on a coin, the coin would be not sharp, but slightly before the coin

 

Thomas, as I tried to explain, I think they may be setting it to give slight front focus when wide-open so that the focus shift back is not so pronounced as you stop down.

 

From memory, mine, which went back for coding before the M8 was even announced, is spot on wide open (to within a cm or so) but clearly focus shifts as I stop down. The depth of field is shown by Leica to be +/- 3.3 cm (roughly) at 1m and f1.4; adjust for the crop factor and your lens is right on the limit, which would suggest there have indeed been some changes to the adjustment point, all in an effort to reduce the visible effects of focus shift, in real images, viewed at normal viewing distances.

 

IMHO, your lens is as correctly adjusted as it's ever going to be, if "correctly adjusted" means a sensible balance of the inevitable compromises. Some, like Guy and Tim Ashley have bailed out, others like me live with it because it's the widest fast lens Leica currently make.

 

In theory, you and I can practice nudging the focussing ring when wide open and close up, though it's hardly scientific!

[Jack_Flesher]

I think both the 35 ASPH and the Sonnar are known to have focus-shift issues. Actually, ALL fast lenses have it to some degree, so the issue may be what aperture is used to set focus initially. I think your best bet is the old-school Leica RF tactic of "learning" the idiosynchrosies of those lenses and make a manual focus adjustment when shooting them at the problem apertures.

 

For example, my 35 Pre-asph Lux is dead on at f1.4, but back-focuses a bit as I stop down to f5.6 where DoF is more than sufficient to make up for it. So I do make slight adjustments, a slight added 0.5 mm twist to the focus ring at f2 thorugh f4. My friend has the Sonnar, and his is on at f2.8 and front-focuses at f1.5, so at f1.5 he has to focus slightly behind his intended point of focus to nail it. Since he uses his primarily for portraits, he has learned to focus on an ear instead of an eye, and then usually nails the eye. The point it, you find a solution that works for you.

 

Cheers,

[tom0511]

Thanks guys.

I knew about the Sonnar focus shift issue and talked to Zeiss. They said me, that in earlier times they calibrated the lens for f2.8 (as a compromise) but lately calibrate for f1.5, because quit some people who buy a Sonnar seem to like using it wide open quit a bit.

Thats why I sent in mine and asked for calibrating the lens for f1.5.

I might be able to live with it since f2.8 I use quit often for portraits (and thats what I want to do with the lens) and I might end up just to focus a little further when using the lens wide open. I also bought it more for the special drawing than forits speed alone.

 

By the way the 50/1.4asph seems tobe very good in this respect: I cant find any focus shift at all.

 

In the case of the 35/1.4asph I dont know yet what to do, probably will use it for awhile and see if the problem is a problem in real life (however I guess that it is).

If so I will end up selling it and just use 28/2.0 or 50mm.

 

Now I await my Noctilux back from Leica but I am afraid that it will still show the same problem, because it also showed focus shift before I sent it in.

 

Thanks again, personally I find focus shift and front/back focus quit problematic for general use, because you quickly loose the advantage of the sharp lenses when slight missfocus occurs. It quikckly makes the difference for me between a 99%-good image and a 90%-good image, if the eyes are slightly out of focus.

 

Thanks again for the suggestions, Thomas