stropello
Newbie
While reading the recent technical documentation about the M9 camera, a few inconsistencies drew my attention. I have tried to alert Leica about them, but it seems that the Company does not have a feedback port on the web. Therefore I post here my doubts, so that others can check them (and possibly Leica can take notice of them, in case they are justified).
1) In the Leica_M_Brochure_2009_en, on page 79, there is a table with the technical data of Leica M Lenses. The third-but-last column of the table reportedly lists the “Closest focus distance from film plane, in mm”. Well, mm should be replaced by cm, since the listed values range from 50 to 150. Moreover, it would be now fair to refer to “focal plane” or “film/sensor plane” instead of barely “film plane”.
2) Regarding now a more subtle matter, the Leica M brochure, the Leica M9 Technical Data pdf file, the FAQ LEICA M9 (Status September 2009) document, and the Leica M9 Instructions, all contain the ensuing sentence: “The size of the bright-line frame corresponds exactly to the sensor size of approx. 23.9 x 35.8 mm at a setting distance of 1 meter. At infinity setting, depending on the focal length, approx. 7.3 % (28 mm) to 18 % (135 mm) more is recorded by the sensor than indicated by the corresponding bright-line frame and slightly less for distances shorter than 1 m.” Since any 135 mm M-lens has a minimum focusing distance of only 1.5 m, it is rather extravagant to have a 135 frameline that frames perfectly at 1 m.
3) Again with regard to the sentence reported at the previous point, I have checked the figures about the increase of coverage from 1 m to infinity. The figure about the 135 mm lens is substantially correct: my estimate for the linear increase is 19.2 %, that corresponds to a 42.0 % surface increase (i.e., 42% additional pixels are exposed with respect to those that cover the image shown in the 135 mm frameline.) On the contrary, the published figure about the 28 mm lens is wrong (and pessimistic too): the true linear increase in coverage is only 3.0 % (which means 6.0 % surface increase).
4) The Leica M Brochure 2009 pdf file, at the bottom of page 64 reads: “Note: The use of this lens on the Leica M9 is recommended only when certain criteria are met, for example, it must be stopped down by at least two stops.” The lens here referred to is the Leica APO – Telyt – M 135 mm f/3.4. Ok, there are no typos here, but this note makes me wonder about its ground. The 135 mm f/3.4 lens does not have - at any given focusing distance – the shallowest depth of field of the whole lineup of M lenses. Therefore the accuracy of the M9 rangefinder should not be the culprit here. Couldn’t it be that the micro-lenses in front of the M9 sensor are too offset – near the sensor edges – for a 135 mm lens?
1) In the Leica_M_Brochure_2009_en, on page 79, there is a table with the technical data of Leica M Lenses. The third-but-last column of the table reportedly lists the “Closest focus distance from film plane, in mm”. Well, mm should be replaced by cm, since the listed values range from 50 to 150. Moreover, it would be now fair to refer to “focal plane” or “film/sensor plane” instead of barely “film plane”.
2) Regarding now a more subtle matter, the Leica M brochure, the Leica M9 Technical Data pdf file, the FAQ LEICA M9 (Status September 2009) document, and the Leica M9 Instructions, all contain the ensuing sentence: “The size of the bright-line frame corresponds exactly to the sensor size of approx. 23.9 x 35.8 mm at a setting distance of 1 meter. At infinity setting, depending on the focal length, approx. 7.3 % (28 mm) to 18 % (135 mm) more is recorded by the sensor than indicated by the corresponding bright-line frame and slightly less for distances shorter than 1 m.” Since any 135 mm M-lens has a minimum focusing distance of only 1.5 m, it is rather extravagant to have a 135 frameline that frames perfectly at 1 m.
3) Again with regard to the sentence reported at the previous point, I have checked the figures about the increase of coverage from 1 m to infinity. The figure about the 135 mm lens is substantially correct: my estimate for the linear increase is 19.2 %, that corresponds to a 42.0 % surface increase (i.e., 42% additional pixels are exposed with respect to those that cover the image shown in the 135 mm frameline.) On the contrary, the published figure about the 28 mm lens is wrong (and pessimistic too): the true linear increase in coverage is only 3.0 % (which means 6.0 % surface increase).
4) The Leica M Brochure 2009 pdf file, at the bottom of page 64 reads: “Note: The use of this lens on the Leica M9 is recommended only when certain criteria are met, for example, it must be stopped down by at least two stops.” The lens here referred to is the Leica APO – Telyt – M 135 mm f/3.4. Ok, there are no typos here, but this note makes me wonder about its ground. The 135 mm f/3.4 lens does not have - at any given focusing distance – the shallowest depth of field of the whole lineup of M lenses. Therefore the accuracy of the M9 rangefinder should not be the culprit here. Couldn’t it be that the micro-lenses in front of the M9 sensor are too offset – near the sensor edges – for a 135 mm lens?
Carlo
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This is almost certainly related to the 0.68 mag and the RF base length not being long enough for accurate focus wide open. More info on RFF accuracy, magnification, RF baselength here.
BTW, some people (like me) view RFF with a white background so if you use white text, nothing shows up.
stropello
Newbie
Thank you, digitalintrigue, for you hints.
I was wrong in presuming that the 135 mm Apo-Telyt has not the shallowest depth of field (DOF) of all M lenses, at any given distance. Actually, it has. The formula on RF accuracy takes into account DOF, too.
My other doubts are still there, though.
Carlo
JRG
Well-known
Oh, you can do better than mere typos!
Grab a copy of the M-system brochure:
http://us.leica-camera.com/service/downloads/rangefinder_cameras/mp/index.html
Go to p. 51, where you will see a display that purports to show the 50mm framelines in the 0.58x, 0.72x, and 0.85x viewfinders.
Fine, except that as you progress from 0.58 to 0.72 to 0.85, the scene shown in the viewfinder remains constant and the size of the 50mm framelines grows smaller. It doesn't work quite that way.
That page has been there for years.
Grab a copy of the M-system brochure:
http://us.leica-camera.com/service/downloads/rangefinder_cameras/mp/index.html
Go to p. 51, where you will see a display that purports to show the 50mm framelines in the 0.58x, 0.72x, and 0.85x viewfinders.
Fine, except that as you progress from 0.58 to 0.72 to 0.85, the scene shown in the viewfinder remains constant and the size of the 50mm framelines grows smaller. It doesn't work quite that way.
That page has been there for years.