M8 Focusing question

[scjohn]

I notice the focus is off when using my M8 and 50 1.4 ASPH. When I focus at close range the point of focus is out of focus and objects a few inches further from the camera are perfect.

Is this likely a lens or a camera issue. I plan to send the lens in to get it coded and I could ask that it be recalibrated at the same time. It is still under warranty. Similarly, it appears I will need to send the M8 in too and I could have that checked as well but I have not seen any complaints about the accuracy of the rangefinder on the M8.

May I have your thoughts please.

[M'Ate]

Can you post a sample ?

Is there any chance this is a focus and recompose issue ?

A 10 degree swing after focussing will result in the placement of the focal plane 1 inch behind the original focus point at about 4 feet. You lose critical focus and with an f1.4 lens wide open, you don't have much to start with.

Apologies if you already know this.

[harmsr]

Stephen,

Does your lens focus out to infinity or stay just a "little" shy to the right?
Does this happen with any of your other lenses?

It seems that the 50 1.4 ASPH has had some focusing issues, as Tony Rose at PopFlash and I can attest to. We went through several samples until I got one that focused correctly.

Ray

[scjohn]

I will post an image. I know I did not move the camera. I took many shots and then shot a monument to confirm. (focusing on the 1st row of letters). I am going to pull out my 90 2.0 and try that. If I use that wide open and the problem doesn't show up I can safely blame the 50.

[scjohn]

Oh, and it looks like it goes all the way to infinite too.

The irony is that I would have never noticed this before. On the M7 I used the 90 for portraits and tried the 50 wide open only because of crop factor.

[jaapv]

Try shooting from a tripod to a fixed object first, using a viewfinder magnifier.. It is highly unlikely that the lens is off. If anything needs adjustment it is with 95% certainty the body, and that is a 5 minute job for any camera technician. Calibrating a lens is a complicated and skilled procedure.

[harmsr]

Jaapv is correct that it normally is the body.

Mount the camera on a tripod and compare it with your other lens. If both are off, it is the body. If only the 50 is off then it is the lens.

Unfortunately, Tony Rose and I recently went through 4 new samples of the 50 Lux ASPH that had focusing issues. I also remember that another forum member posted he had a focusing issue with a 50 Lux ASPH on his M8 and sent both to Solms for evaluation.

Best.

Ray

[carstenw]

It was me who had issues with the 50 Asph. The first copy I got was clearly out. The second copy was better, but I still could not focus on infinity. Neither would focus accurately at the near limit, so off camera and lens went to Solms. I hope they come back soon. I don't know if the near-limit focus problem is just the way it is, or if it is meant to work. It is a pretty hard test for an RF camera.

[scjohn]

It looks like it's the lens. (The focus appeared perfect on the 90). Of course thanks to you guys this discovery has me crying like a baby now that the camera fix has been described as a 5 minute job and the lens fix as "complicated."

I do need to check one last think. I shot with "lens coding detected" and the 50 is not yet coded. Maybe that makes a difference. Then again, maybe the depth of field difference between shooting wide open at 1.4 on the 50 and 2.0 on the 90 allows me to see the problem on the 50 but not the 90.

Focusing sure looks great at 4.0 with the tri-elmar!

[harmsr]

Sounds like you also got one of the non-focusing 50 Lux ASPH lenses.

The coding setting will have nothing to do with it.

Get another lens.

Best,

Ray

[mhleo]

I actually have the same issue with my Noctilux, but not with the 90mm, so it is definitively the lens...

[carstenw]

If you only have two lenses, you don't know which one it is... Try to go to your Leica store. They most likely have a known-good camera you can compare with.

[rick_dykstra]

Carsten, I think you mentioned that it is asking a lot of a rangefinder to be bang on accurate at the closest focussing. I have found that my lenses tend to back focus at close range and so I compensate by focussing just a little closer than the rangefinder suggests. This is most evident with my 35/1.4 Asph, with its 0.7m up close point and narrow depth wide open. Before I started using my 'focus tweak' method, ears tended to be sharper than eyes.

Sometimes it's just a matter of getting to know the personality of lenses and bodies. And if I need perfect focus up close, I reach for an R8.

Here's something to ponder (apologies to those who've heard this from me before).

A properly calibrated rangefinder places the focal plane in such a way that 1/3rd of the acceptably focussed zone is in front of the focussing point and 2/3rds behind. There is no ability for the eye to assess how the focus looks. It is an objective process. The 'middle' of the depth will appear to be behind what we focussed on. It might look like it is back-focussing.

With an SLR and when using a ground glass screen we focus subjectively and will tend to place the middle of the depth of field on the focussing point. We naturally tend to front focus a little.

Experimenting with this concept is not so easy with film. Step up the M8!

[guy_mancuso]

I checked my 50 1.4 lux again this week. What amazes me is how sharp this lens is wide open

[yuweimichael]

I also have problem with focus . I am new in Leica camera. I use M8 now. What's good techniques to get a "focus" image ? It's kind of hard for me to get one correct focus image.
I use 50 and 21mm. ANy suggestion to a new player ? Thanks.

[TonyField]

Originally Posted by scjohn

I notice the focus is off when using my M8 and 50 1.4 ASPH. When I focus at close range the point of focus is out of focus and objects a few inches further from the camera are perfect.

Hopefully, someone with current technical knowledge can comment on this. However, from ancient experience with the original 90mm F2 summicron......

Since lenses never have "exactly" the focal length is is designed for, after the lens elements are assembled to make a lens, the exact focal length is determined by measurement. A focus cam is selected / ground to match the optics. The error in focal length measurement and cam profile shape fall within "engineering tolerances". Historically, the near focus point acceptable error in focus point allowed the lens to be out-of-focus with the lens wide open. I think Leica had an f-stop and associated DOF that was considered "within spec". For example, at a 4 foot focus distance, my old 90mm F2 focused distinctly to the rear of the actual point of focus on my two M2 , 2 M3 bodies.and one M5 body. Leica stated that my lens was in-spec and would not repair.

SInce Leica engineering is quite precise, but does have a built in acceptable error range, I think your lens is at one limit of being in-spec and the camera is at the other limit. The net result is that you have a serious focus issue with close-in subjects.

It would be nice if Leica would comment upon the focus specifications of the camera and the lens.

[jaapv]

And then there is focus shift: Stop a lens down and the plane of focus will shift. One of the lenses well known for this is the Noctilux, the focus point shifts towards the camera on stopping down.Other lenses I do not know the exact parameters, but it stands to reason the same effect will be exhibited to some degree. So we also have to ask: at which aperture is your lens misfocussing? I don't even know at which aperture Leica standarizes their focus.

[marknorton]

I think focussing is the Achilles Heel of Rangefinder cameras because not only does the camera have to be perfect, so too does every lens and this adds to the cost and complexity of the lenses.

With an SLR, providing the relationship between the lens mount, focal plane, focussing screen and mirror alignment - all in the body - are correct, then any lens can be mounted on the camera; if the image is sharp on the focussing screen, it will be too in the image.

With a Rangefinder body, there's a precise relationship between the position of the roller and the viewing distance at which the main and rangefinder images coincide. To maintain compatability with existing lenses, Leica had to design the M8 to reproduce the relationship exactly, in spite of the different thickness of the body and the lens mount and focal plane being moved forwards.

For each lens, the profile of the cam has to match the standard across the entire focussing range. I do not know whether the cam is ground for each individual lens or whether manufacturing tolerance are such that a standard profile for each lens type.

[ho_co]

Originally Posted by marknorton

For each lens, the profile of the cam has to match the standard across the entire focussing range. I do not know whether the cam is ground for each individual lens or whether manufacturing tolerance are such that a standard profile for each lens type.

Mark--
Historically, Leica had a range of cams for each lens. To my knowledge the cams were never ground to match, but the cam was chosen which was closest to the actual focal length.

The 'actual focal length' or probably more correctly the 'cam focus' is engraved on the lens barrel for lenses 50mm and longer. That engraving is the two small digits just beyond the infinity end of the focus scale, and consists of the last full milimeter and first decimal of the focal length.

One reason the DR Summicron has such a good reputation is that all Dual-Ranges were exactly 51.9 mm, the design focal length. Because the lens had two focus cams, it would have been too expensive to produce a different mount for several focal lengths.

--HC

[handcoater]

When I had my M8, and one of the reasons I did not keep it was that my 21 2.8, 35 f2, 50 f2 and 90 3.5 all focused spot on (wide open) in very careful testing. The same careful testing with the 50 Noct, 50 1.5 CV Nokton and 35 1.2 CV Nokton showed that all three lenses backfocused (wide open) by about 2 inches at 3 feet and 10-15 feet at 30-40 feet focus distances. it was maddening because all three lenses were very sharp... someplace else!