One for the techies: Leica R 21-35mm Vario Focusing Issue

[AbbeyFoto]

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I am looking at a Leica R 21-35mm Vario lens with a bit of history. While physically mint the lens has a focus issue which Leica is reluctant to acknowledge and fix. I will do some careful tests to try to persuade them there is an issue; I am confident there is a problem. My guess they are applying inadequate testing to a discontinued lens. I assume their tests will be done in a lab on some test bed following some routine procedure. My fear is that that routine does not adequately test the Vario (zoom) dimensions of this lens. My problem is I do not really understand the technology. I am no engineer so I am intrigued how a true zoom control can work. I had a look at Edwin Puts new Leica Compendium which hinted at there being three optical groups, one of which controls the basic properties, one controls the magnification and one that adjusts the focus position. To me as layman this makes sense even if I have no idea how that is possible. I am used to the experience that if I turn the ring to control effective focal length then the focal point does not change - that I believe is the point of a true zoom (Vario in Leica's terminology?) lens. So here I have a "zoom" where focus is set to infinity and while that is accurate at 35mm it is increasingly inaccurate as I zoom down toward 21mm. If I use the screen to focus at a distant object at 21mm the distance ring is a good deal away from infinity (less than 15 metres). The lens I have is not a zoom lens? It is a variable focal length lens? When I focus using the screen and ignore the setting on the focus ring then things seems to be fine - though focusing a 21mm lens is not easy even on a R9.

 

If anyone has any idea what might be wrong with this lens I would welcome your input as I prepare my case to Leica.

[masjah]

I am looking at a Leica R 21-35mm Vario lens with a bit of history. While physically mint the lens has a focus issue which Leica is reluctant to acknowledge and fix. I will do some careful tests to try to persuade them there is an issue; I am confident there is a problem. My guess they are applying inadequate testing to a discontinued lens. I assume their tests will be done in a lab on some test bed following some routine procedure. My fear is that that routine does not adequately test the Vario (zoom) dimensions of this lens. My problem is I do not really understand the technology. I am no engineer so I am intrigued how a true zoom control can work. I had a look at Edwin Puts new Leica Compendium which hinted at there being three optical groups, one of which controls the basic properties, one controls the magnification and one that adjusts the focus position. To me as layman this makes sense even if I have no idea how that is possible. I am used to the experience that if I turn the ring to control effective focal length then the focal point does not change - that I believe is the point of a true zoom (Vario in Leica's terminology?) lens. So here I have a "zoom" where focus is set to infinity and while that is accurate at 35mm it is increasingly inaccurate as I zoom down toward 21mm. If I use the screen to focus at a distant object at 21mm the distance ring is a good deal away from infinity (less than 15 metres). The lens I have is not a zoom lens? It is a variable focal length lens? When I focus using the screen and ignore the setting on the focus ring then things seems to be fine - though focusing a 21mm lens is not easy even on a R9.

 

If anyone has any idea what might be wrong with this lens I would welcome your input as I prepare my case to Leica.

 

I've got a 21-35 R zoom. As you say, it's not at all easy to focus with a reflex camera at 21mm focal length. But, for what it's worth, I've just tried mine with the right angle viewfinder (because it's got a 2x magnification facility) and, so far as I can tell, the setting on the focus ring does not have to be changed as I zoom from 21 to 35.

 

I think you are correct about the nomenclature. As I understand it, strictly speaking a zoom lens preserves the focus setting as it is zoomed, otherwise it is a variable focal length lens. I've heard it said by some that some samples of the "collector's item" 35-70 2.8 zoom had this problem

 

Hope this helps.

[tomlianza]

I own this lens and it is one of the best zooms I have had. I am thinking of modifying for it my D3X and D800E(still on order). I have not detected any focus shifts on the M9/DMR combination. The only reason that I haven't changed the mount to Nikon is that I am holding out on a potential solution from Leica for all this fine legacy glass.