What M lenses can't be coded?

[hammam]

I read and there that third party lenses can't be coded for the M8. Is this true? Why couldn't CV and Zeiss lenses in M mount, for instance, be coded? And I also read that you can't even code the Summicron 40, framelines problem notwithstanding? Don't they all share the same mount as Leica M lenses? I don't get it. Anybody knows something about that? Thank you.

[robsteve]

The coding allows Leica to do image correction in the camera to correct things like vignetting. It would be unreasonable to expect Leica to analyze third pary lenses and put them into the camera firmware as well.

I suppose the third parties could try picking a leica lens close in performance and use that code. It may introduce odd problems like if the Leica version vignetted a bit less, the vignette correction might get the corners of the third party lens but leave some vignetting mid way through the frame which would be very hard to correct later.

I am thinking that with the Voitlander lenses that use a screw to M adapter, some enterprising individual could code some of these adapters to match some of the Leica lenses with similar focal lengths and performance.

From an earlier thread on ROM lenses and the DMR doing image correction, here are a couple examples illustrating what I mean.

Here is a 19mm shot done with the DMR and the ROM contacts disabled. This is a shot of my light table which is neither clean nor evenly illuminated. Just look for the corner vignette, not top to bottom even illumination. You can notice the corner vignetting of the lens.



Here it is with the ROM enalbled and the Camera doing the vignetting correction. This correction is even visible on the DMR display, so it is being done in the camera.



This is the first image and I applied some vignette correction in the DNG conversion. I applied the wrong amount, but just to illustate what you could get if the third pary lenses were coded and were not identical to the Leica lens. Remember, on the M8 this correction is being done in the camera, before writing the DNG or Jpeg.

[hammam]

Originally Posted by robsteve

The coding allows Leica to do image correction in the camera to correct things like vignetting. It would be unreasonable to expect Leica to analyze third pary lenses and put them into the camera firmware as well.

I suppose the third parties could try picking a leica lens close in performance and use that code. It may introduce odd problems like if the Leica version vignetted a bit less, the vignette correction might get the corners of the third party lens but leave some vignetting mid way through the frame which would be very hard to correct later.

I am thinking that with the Voitlander lenses that use a screw to M adapter, some enterprising individual could code some of these adapters to match some of the Leica lenses with similar focal lengths and performance.

From an earlier thread on ROM lenses and the DMR doing image correction, here are a couple examples illustrating what I mean.

Here is a 19mm shot done with the DMR and the ROM contacts disabled. This is a shot of my light table which is neither clean nor evenly illuminated. Just look for the corner vignette, not top to bottom even illumination. You can notice the corner vignetting of the lens.



Here it is with the ROM enalbled and the Camera doing the vignetting correction. This correction is even visible on the DMR display, so it is being done in the camera.



This is the first image and I applied some vignette correction in the DNG conversion. I applied the wrong amount, but just to illustate what you could get if the third pary lenses were coded and were not identical to the Leica lens. Remember, on the M8 this correction is being done in the camera, before writing the DNG or Jpeg.

I don't think the coding tells anything else to the camera than the focal length and the maximum aperture of the lens. I don't think it transmits any kind of analyse of the optical properties of the lens. The vignettting is a matter of focal length and aperture. So, what difference is there to the coding and camera between a Summicron 50/2 and a Zeiss ZM 50/2?

[robsteve]

The coding allows image correction. On Reid Reviews report of the M8 (Welcome to ReidReviews) he showed examples with the coding turned on and off and there was definately image correction going on regarding vignetting.

If the Zeiss 50mm did not have the same image correction properties as the Leica 50mm, the coding function of the M8 and its image correction algorithims might make the Zeiss image worse, such as my third sample image above.

On the DMR I also see that the ROM is not just doing density corrections in regard to vignetting, but color corrections as well. Notice how the corners go cyan when I try correcting the vignette at the DNG conversion stage, rather than using the ROM correction of the camera.

[craigrmurray]

Originally Posted by hammam

I don't think the coding tells anything else to the camera than the focal length and the maximum aperture of the lens. I don't think it transmits any kind of analyse of the optical properties of the lens. The vignettting is a matter of focal length and aperture. So, what difference is there to the coding and camera between a Summicron 50/2 and a Zeiss ZM 50/2?

Olivier:
I think the coding problem for other lenses is that the bottom flange of the lens is removed and replaced with the coded one, rather than the coding being inscribed or painted onto the old flange. I doubt Leica would offer that service for other manufacturers' lenses, although I see no reason why it couldn't be done by someone else, assuming the Leica flange would fit the Zeiss or the CV, or could be machined to do such.

Also, the wider CV lenses are screw-mount, and require a bayonet adaptor. I'm assuming Leica is not planning on offering a coded Screw-mount to M bayonet adaptor, since the targeted screw-mount lens would be unknown.

Just my two cents worth.

[ho_co]

Olivier--
As others have remarked, Leica isn't going to code some other brand of lenses. If you want the benefits of the zebra code, you need the Leica lens. Mercedes won't do adjustments on BMW's.

But remember for the 40mm Leica lens: There is no guarantee that it will work on any particular M body, so Leica will not code it.

When I asked Leica whether standards for M rangefinders had changed from the days of the CL, I was told simply that the C lenses are not recommended for M bodies and the M8 is an M body. The C lenses work on about 75% of previous M bodies, so the same may hold true here.

--HC

[Zurenborger]

Oliver funny you shloud mention this, but my mercedes 250sl (very old model) is actually serviced by my BMW dealer, they love doing it, it gets the extra attention and it's always a job done well ...


just thought I'd mention it :-)

[hammam]

Originally Posted by ho_co

Olivier--
As others have remarked, Leica isn't going to code some other brand of lenses. If you want the benefits of the zebra code, you need the Leica lens. Mercedes won't do adjustments on BMW's.

But remember for the 40mm Leica lens: There is no guarantee that it will work on any particular M body, so Leica will not code it.

When I asked Leica whether standards for M rangefinders had changed from the days of the CL, I was told simply that the C lenses are not recommended for M bodies and the M8 is an M body. The C lenses work on about 75% of previous M bodies, so the same may hold true here.

--HC

The Summicron 40 works beautifully on any M. The only thing is that you get the 50 framelines in the VF. What I usually do is call the 35 framelines and frame a bit wider. But, hey, with the M8, given the 1,3 factor (40 equivalent = 52), the 50 framelines will be just perfect, I suppose. I can live without the coding in a 40 mm lens. I love my 40.

[hammam]

Originally Posted by hammam

The Summicron 40 works beautifully on any M. The only thing is that you get the 50 framelines in the VF. What I usually do is call the 35 framelines and frame a bit wider. But, hey, with the M8, given the 1,3 factor (40 equivalent = 52), the 50 framelines will be just perfect, I suppose. I can live without the coding in a 40 mm lens. I love my 40.

Wait a minute. Sorry to digress, but come to think of it... If the 40 Summicron calls the 50 framelines in the M8, like it did with other Ms, these will show actually the FOV of a 65 mm lens. Right? So, I'm wrong here, since the 40 will finally give a FOV of a 52, not a 65. I guess I will have to do exactly the same thing as before, ie manually call the 35 framelines to get what will actually amount to a 46 mm lens FOV in the VF. Let's sum it up: with 35 mm framelines, the photo will actually have a 6 mm wider FOV (46 vs actual 52). Which is on the safe side. If I shoot the 50 framelines, the photo will actually have a 13 mm narrower FOV (65 vs actual 52). which is dangerously tight. Do I make sense? Help! LOL!.

[craigrmurray]

Originally Posted by hammam

Wait a minute. Sorry to digress, but come to think of it... If the 40 Summicron calls the 50 framelines in the M8, like it did with other Ms, these will show actually the FOV of a 65 mm lens. Right? So, I'm wrong here, since the 40 will finally give a FOV of a 52, not a 65. I guess I will have to do exactly the same thing as before, ie manually call the 35 framelines to get what will actually amount to a 46 mm lens FOV in the VF. Let's sum it up: with 35 mm framelines, the photo will actually have a 6 mm wider FOV (46 vs actual 52). Which is on the safe side. If I shoot the 50 framelines, the photo will actually have a 13 mm narrower FOV (65 vs actual 52). which is dangerously tight. Do I make sense? Help! LOL!.

Olivier:

You are correct. I just mounted the 40mm Summicron-C on the M8, and indeed it does bring up the 50-75 frame. So you will have to preview the 24-35 frameline, just like you do on your Ms.

It's funny, I thought the same thing you did the other day concerning the 40 'cron.