Hi

I have a question about my non ASPH 35 Summilux with eyes. I have spoken to Reinhold Mueller and Gerry Smith (leica techs in Toronto) about having the eyes removed which may cause a possible problem of accurate focusing at wide apertures. They both state that the eyes only affect the perspective of the finder and that removing them does not affect the rangefinder's ability to focus at any aperture. With the exception that the close focusing ability that the eyes offer is now gone. I have read in previous posts that people have stated the opposite; that removing the eyes does affect the focusing ability. So now I'm confused. Does anybody have any thoughts on why there are differing opinions? Thank you in advance for any answers.

Erik

-- Erik Loponen (eloponen@hotmail.com), August 15, 2001

Answers

Reinhold is correct, there should be no difference focusing this lens with or without the goggles. Remember that the exact same lens was made w/o the goggles.

BTW, if you are using this lens on an M3 and have the goggles removed you can cover up the center window with a piece of electrician's tape and the outer edge of the viewfinder should just about match the acceptence angle of the lens. Covering up the center window eliminates the projected frames.

-- Bud (budcook@attglobal.net), August 15, 2001.

In fact the focusing accuracy should be *improved* without the goggles, because they *reduced* the effective baselength of the rangefinder.

-- Jay (infinitydt@aol.com), August 15, 2001.

I never had the Summilux with eyes, but I did have several models of the Summaron and in an effort to reduce the size of the lenses, I did try to remove the eyes, (easy, only two screws) when I moved from the M3 to the M2. The focus was effected. The cam on the lens has a different slope to match the rangefinder's optical modification due to the eyes. The deviation was the same for both the f/2.8 and f/3.5 Summarons when the eyes were removed.

I would only take you about two seconds to see that the distances are no longer accurate when focused without the eyes. I begrudgingly reinstalled the eyes, and bought a proper lens for cameras that support the 35mm lens.

-- Al Smith (smith58@msn.com), August 15, 2001.

>The cam on the lens has a different slope to match the rangefinder's optical modification due to the eyes<

Al: Are you saying that the RF mechanism is optically altered (ostensibly by a parallax change between the two rf windows) by attaching the eyes, and hence the slope of the focus cam needs to be altered to accomodate the change? It does not make sense to me that magnification alone could be responsible for such differences, or the different VF magnifications between models would need different cam slopes.

-- Jack Flesher (jbflesher@msn.com), August 15, 2001.

Jack,

I am not an optical engineer, but I am 100% percent certain that when the eyes were removed, and correct focus was indicated by the rangefinder, the lenses would not be at the proper distance. Upon examining the Summarons, (both a f/3.5 and f/2.8) with a non-eye'ed Summaron, it was clear that the steepness of the follower cam on the lenses were in fact different.

If there was not an optical variation induced into the rangefinder system, then there would not be two eyes. All that would be needed would be the eye over the actual viewfinder, to give the angle of the wider lens.

Again, I am only giving my experience... two different lenses on three M bodies... same results. With the eyes removed, the lenses were not in focus when the rangefinder said they should have been. Re-installation of the eyes immediately resolved the problem.

-- Al Smith (smith58@msn.com), August 15, 2001.

I did a quick 5 minute search of the LUG archives on the subject of removing the eyes from the older 35mm lenses and found a lot of corroborating experiences with my findings (above). Below are just three, one which a Leica repairmen actually quotes a price to modify the focusing cam to work with the eyes removed, (and a warning that the modification would not allow the eyes to be reattached again because the focusing would be altered).

http://mejac.palo-alto.ca.us/leica-users/v18/msg13292.html

http://mejac.palo-alto.ca.us/leica-users/v07/msg06444.html

http://mejac.palo-alto.ca.us/leica-users/v00/msg04698.html

-- Al Smith (smith58@msn.com), August 15, 2001.

Everbody thank you for your answers. This will really help me with deciding whether i keep the lens or trade it in.

-- Erik Loponen (eloponen@hotmail.com), August 15, 2001.

I tried it, and the lens did not focus accurately without the eyes. Not even close.

-- Andrew Schank (aschank@flash.net), August 15, 2001.

Well I guess I lost all credibility but so did Reinhold Mueller:-)

-- Bud (budcook@attglobal.net), August 15, 2001.

Hi Erik,

Removing the eyes of a 35mm lens will actually increase sensitivity of the rangefinder. This is because the magnification of the 35mm lense is less than unity and the effective measurement base of the rangefinder is reduced as it is the product of base length times magnification. For a 135mm lens with eye, removing the eye will decrease sensitivity as magnification of the eye is larger than unity.

However, the rotation angle in the rangefinder is proportional to the effective base and as such when the eye is removed the cam of the lens has to be modified. This means if the cam is calibrated correctly it should be more accurate in focusing.

For more detail information, you can read "camera rangefinders" in chapter 12 of the classic book of Rudolf Kingslake, "Optics in Photography"

Regards

Patrick

-- Patrick So (patrikso@hkstar.com), August 16, 2001.