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jaapv · 05/13/08, 08:42 AM

Interesting issue. There have been, over the years, many publications on the accuracy of rangefinder focussing vs. SLR focussing. For a synopsis I recommend either the "Leica M-advanced photo school" book by Günther Osterloh, which has tables and graphs, or Jonathan Eastland's "Leica M compendium".
To say anything sensible, we must, of course, compare manual SLR focussing with manual RF focussing. This can be expressed in a simple, linear graph. With a 0.72 viewfinder the RF is magnitudes more accurate at 21 mm and the SLR draws level at just under 135 mm, to go on to be more accurate as focal length increases. With the M8 rangefinder at 0,62 I would put the value where the graphs cross at 90 mm.
Nowadays there are comparisons between manual RF focussing and Autofocus SLR's. Personally, but one would have to work it out, I feel that the RF wins in accuracy, certainly up to and including 50 mm. If the theoretical 90 mm is really as easily obtained as theory suggests (and the same goes for the 75 Summilux), may be doubtful imo. The digital-mechanical coupling is probably more consistent that the human eye-brain-hand coordination though.

Erwin Puts' 1.5 % is clearly more close to the actual plane of focus than the official tolerance that Canon uses which is "within 1/2 DOF" (at the COC of the relevant format).
Much as I hate to shift the blame to the user, the factors of dexterity and eyesight, notably unnoticed astigmatism, are the main contributing factor to the problems that are seen with rangefinder systems. A matte screen is easier on the eye than the angle comparison of a rangefinder patch. The visibility of the DOF helps the eye as well in judging sharpness. I notice, especially with long lenses, that I "walk" the plane of focus through the projected image to get accurate.
Of course, a sensor's exactitude and instant review throw the spotlight on the placement of the plane of focus. It would be interesting to do a scientific comparison between an M8 and a manually focussed 1.3x crop camera. I think I am off with my DMR at least as often as I am with the M8,possibly more often, but I do not keep statistics.

05/13/08, 08:42 AM	#2 (permalink)
jaapv Erfahrener Benutzer Join Date: 09/14/04 Location: Hellevoetsluis, Netherlands Posts: 6,040	Re: Accuracy of M8's rangefinder system Interesting issue. There have been, over the years, many publications on the accuracy of rangefinder focussing vs. SLR focussing. For a synopsis I recommend either the "Leica M-advanced photo school" book by Günther Osterloh, which has tables and graphs, or Jonathan Eastland's "Leica M compendium". To say anything sensible, we must, of course, compare manual SLR focussing with manual RF focussing. This can be expressed in a simple, linear graph. With a 0.72 viewfinder the RF is magnitudes more accurate at 21 mm and the SLR draws level at just under 135 mm, to go on to be more accurate as focal length increases. With the M8 rangefinder at 0,62 I would put the value where the graphs cross at 90 mm. Nowadays there are comparisons between manual RF focussing and Autofocus SLR's. Personally, but one would have to work it out, I feel that the RF wins in accuracy, certainly up to and including 50 mm. If the theoretical 90 mm is really as easily obtained as theory suggests (and the same goes for the 75 Summilux), may be doubtful imo. The digital-mechanical coupling is probably more consistent that the human eye-brain-hand coordination though. Erwin Puts' 1.5 % is clearly more close to the actual plane of focus than the official tolerance that Canon uses which is "within 1/2 DOF" (at the COC of the relevant format). Much as I hate to shift the blame to the user, the factors of dexterity and eyesight, notably unnoticed astigmatism, are the main contributing factor to the problems that are seen with rangefinder systems. A matte screen is easier on the eye than the angle comparison of a rangefinder patch. The visibility of the DOF helps the eye as well in judging sharpness. I notice, especially with long lenses, that I "walk" the plane of focus through the projected image to get accurate. Of course, a sensor's exactitude and instant review throw the spotlight on the placement of the plane of focus. It would be interesting to do a scientific comparison between an M8 and a manually focussed 1.3x crop camera. I think I am off with my DMR at least as often as I am with the M8,possibly more often, but I do not keep statistics. __________________ Jaap WWW.JAAPVPHOTOGRAPHY.EU Skype: JAAPVPHOTOGRAPHY Last edited by jaapv : 05/13/08 at 09:11 AM.