75 Summicron Asph - focus out at infinity?

[hoppyman]

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In the interest of providing one other sample I put my APO 75 ASPH. on my M8 and a good tripod and tested that particular lens.

That particular lens was adjusted for me in Solms (after my M8 upgrade) a couple of months ago. "your lenses are good, we can make them better!"

Focusing carefully with a 1.25 magnifier, the best rangefinder coincidence on subjects I guess one kilometer away and out to lunar orbit and the milky way is exactly where the focus ring stops at the infinity marking. There is no play whatsover in the focus movement nor any travel at all even a fraction of a millimetre past that infinity mark. I have yet to try focusing slightly short to try to compare image sharpness. I had thought that DoF would mask any slight error there?

This test at least is on a known just calibrated M8 and lens.

I hope that helps for comparison

[carstenw]

Depth of field is a funny thing. The DoF calculations give an area of "acceptable" focus, where "acceptable" is chosen with the size of the circle of confusion. However, maximum sharpness is only achieved at the plane of focus, and it is possible to see the difference.

[hoppyman]

Depth of field is a funny thing. The DoF calculations give an area of "acceptable" focus, where "acceptable" is chosen with the size of the circle of confusion. However, maximum sharpness is only achieved at the plane of focus, and it is possible to see the difference.

Yes certainly. I more typically use that lens at a couple of metres so I can't say anything definitive about infinity sharpness. Being able to observe any reproducible error of course is dependant on all of the other factors too. I shall try some deliberate tests and do some pixel peeping

[carstenw]

Btw, I didn't make any prints from those tests, so I don't know if the differences are visible in the real world. They were on my screen, though, so now I always focus properly, no matter what distance.

[giordano]

Depth of field is a funny thing. The DoF calculations give an area of "acceptable" focus, where "acceptable" is chosen with the size of the circle of confusion. However, maximum sharpness is only achieved at the plane of focus, and it is possible to see the difference.

 

Agreed; that's why I used a tiny 0.005mm circle of confusion in my post earlier in this thread. That's smaller than the M8's pixel spacing, so even if the lens is sharper than that at the plane of focus the sensor won't be able to reproduce it.

[ho_co]

Focusing carefully with a 1.25 magnifier, the best rangefinder coincidence on subjects I guess one kilometer away and out to lunar orbit and the milky way is exactly where the focus ring stops at the infinity marking. There is no play whatsover in the focus movement nor any travel at all even a fraction of a millimetre past that infinity mark. I have yet to try focusing slightly short to try to compare image sharpness. I had thought that DoF would mask any slight error there?

Geoff--

The lens' infinity stop and the rangefinder should align at infinity just as yours do.

 

If your lens were to focus beyond infinity, depth of field won't help because "beyond infinity" the optical equations go haywire.

[Seeingeye]

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A quick update on the current situation with my copy of this lens, which is now back in Germany along with my M8. According to Leica, the lens needs both adjustments and parts - a familiar story judging by what others have said on this forum. In addition, the camera's rangefinder is also being adjusted as well as having the sensor cleaned. The M8 is still under warranty, so it is not clear whether the rangefinder was actually out of alignment or Leica is simply taking the opportunity to give it a courtesy service.

 

According to both the dealer who sold the lens to me and Ivor at Red Dot Cameras who is sorting out the repair with Leica, it is common for the 75 Summicron to function satisfactorily with film, but require an adjustment for digital use. The reasons for this remain unclear to me. Pity the supplying dealer did not mention it before I bought the lens, knowing full well I was testing it on the M8 ...........

 

Regards

 

Mike

[hoppyman]

Mike, note that your camera will come back with an additional 12 months warranty on the whole camera after the original warranty expires. They should calibrate your sensor positioning as well as the rangefinder for you and then ensure that superb 75 is in tolerance. Mine was checked and adjusted under warranty in Solms when my M8 was upgraded. I had never seen any issue with it anyway. I can tell you that it is superb on both that M8 and my M9 now. Even down at minimum distance and wide open mine focuses EXACTLY where I set it.

As to anecdotal comments that the lenses are 'fine with film but may need adjusting for digital' keep in mind that the sensor does not have the thickness tolerance of film and you are now able to pixel peep to examine any possible deviation from perfect that may have always been there but was undetected with film. In any event the only thing that counts is how YOUR hardware works for YOU. Yours is capable of stunningly good results.

[adan]

Just an additional note that my 75 'cron also focuses "to infinity and beyond" when set according to the focus ring scale/stop. On an M9, btw, on which my other lenses all hit infinity perfectly.

 

The RF images align at infinity (on things really really far away) when the ring is at infinity - but nothing in the picture all the way to the horizon is quite sharp. Defocusing a touch on the near side improves the infinity resolution.

 

10 meters to 1 meter, the RF/focus alignment is perfect. From 1 meter to .7 meter, it front-focuses up to about 5mm.

 

I've handled other 75 'crons that also seemed to do this.

 

Personally I suspect the floating element adds a whole quantum level of complexity to the adjustments needed to get 75 'crons just right (they are the longest M lens with an FE).

 

I mostly use mine for close work, under 3 meters, so I've lived with it - but I am getting a cheap used 90 f/2.8 as a stand-by short tele so that I can send the 75 off for a nice 4-month R&R in Solms.

[rob_x2004]

Personally I suspect the floating element adds a whole quantum level of complexity to the adjustments needed to get 75 'crons just right

 

Personally I think it is likely Leica was jsut having bayonet problems round about the time they were getting M8 out the door. That translates to the rangefinder unit being all over the shop. Someone who probably knows put it to me like that but I guess its just heresay. I had bayonet work done on a film body and on return the 75/2 which was perfect and never went in to service wound up shanked. Leica then adjsuted teh 75 to whatever condition they created in the body because it was probably easier than getting to the bottom of the problem.

 

Ps ... Did I hear someone say they had a new alignment jig now?

[melissah]

If I may add one small point. The infinity focus point is also affected by temperature, as lens/camera components may expand/contract a little. This is why many lenses will actually focus past the infinity mark on the barrel.

 

this is one of the smartest things ive read on this forum.

it makes perfect sense to me.

ive noticed a slight difference in the feel of the focusing ring on the lens when im

in my las vegas home vs my beach home.

one is the desert and the beach is obviously far more humid.

 

ive thought perhaps the lenses do react to the environment.

since i have zero training in this i thought i was just making up conclusions based on feel rather than conclusive science.

clearly nicole knows what she talking about.

 

thanks Nicole very interesting stuff.

no worries i will never stand between an old bat and her leica,

especially when shes a smartie!

best melissa

[rob_x2004]

Not to the amount some lenses are out at infinity or the amount of mispatch at infinity. Also it would appear that one can have close focus right, infinity patch right, and nothing right in between. Its an assembly thing not the weather.

[adan]

Not to the amount some lenses are out at infinity....

 

Actually, most telephotos, at least as far back as the Canon fluorite lenses of the 70's and Nikon's ED 180 and 300's of the 80's, have had focus rings that focus past the infinity mark.

 

Precisely because getting hot in the sun will cause enough expansion in the metal barrel to prevent infinity focus if the leeway was not provided.

 

Especially if the glass is low-dispersion glass: Nikon ED, Canon L/fluorite, Leica APO

 

Nikkor 180mm f2.8 ED infinity focus - Photo.net Nikon Forum

Canon 100-300 fd zoom infinity focus

 

At the links below you can see images of Canon 300mm lenses and see the "L"-shaped mark for infinity setting - which indicates that infinity focus may be anywhere in a range, depending on temperature expansion:

 

Canon FD Zoom 100-300mm lenses

Canon FD 300mm Telephoto lenses

 

So it can be a factor, espcially with APO lenses, but I suspect manufacturing errors in the case of the 75 f/2.

[Seeingeye]

Mike, note that your camera will come back with an additional 12 months warranty on the whole camera after the original warranty expires. They should calibrate your sensor positioning as well as the rangefinder for you and then ensure that superb 75 is in tolerance. Mine was checked and adjusted under warranty in Solms when my M8 was upgraded. I had never seen any issue with it anyway. I can tell you that it is superb on both that M8 and my M9 now. Even down at minimum distance and wide open mine focuses EXACTLY where I set it.

As to anecdotal comments that the lenses are 'fine with film but may need adjusting for digital' keep in mind that the sensor does not have the thickness tolerance of film and you are now able to pixel peep to examine any possible deviation from perfect that may have always been there but was undetected with film. In any event the only thing that counts is how YOUR hardware works for YOU. Yours is capable of stunningly good results.

 

Thanks for the info, Geoff. I am certainly looking forward to having the lens perform as it should! Ivor at Red Dot has not mentioned the extension to the warranty, but I'll check it out with him. If I am without the camera for as long as adan (Andy) suggests, it would at least be some recompense.

 

Regards

 

 

Mike

[rob_x2004]

Sorry about he confusion Adan I was talking about the 75/2, not some canon telephoto. Like I said metal expansion has nothing to do with the amount of out of focus at infinity nor the patch mismatch in probably close to 100% problem lenses. Its an assembly quality control problem probably at the camera body and probably has something to do with poor bayonet tolerances.

[rod99]

Interesting thread. I have had the opportunity to test a fairly large number

of second-hand M lenses on my M8. My experience suggests that many of

the lenses produced before the M8 came out (ie for film cameras) do not

focus to infinity - the majority focus at something between 50 and 100 meters

when set to the infinity stop. This, therefore, has nothing to do with the

rangefinder being "out". The worst offenders (so far) have been the 35 and

50 lux. I would recommend that anyone thinking of buying any secondhand

lens should try it first. Just take it out in the street, set to infinity and fire off a

couple of shot with lens wide open. Then look at results "in camera" magnified

to maximum. Culprits are fairly easy to spot.Just be choosy when buying.