Thomas W
Member
I borrowed the classic Contarex 21mm/f4.5 Biogon with a special adapter for M-mount, and used it on the R-D1. There is no rangefinder coupling, of course. But I find the lens is doing something funny to the metering. If I shoot into the light, e.g., sunset, with huge expanses of clouds, etc. , even if I down the EV to minus 2, the centre of the picture is still a big ball of light, with no distinct shapes. The pictures are very good if I do not shoot into the light, with hardly any vignetting.
I read somewhere that such non-retrofocus lens puts the rear elements too close to the meter, and that the lights do not meet the meter at a perpendicular angle, etc.
What is the problem here?
Thomas W
I read somewhere that such non-retrofocus lens puts the rear elements too close to the meter, and that the lights do not meet the meter at a perpendicular angle, etc.
What is the problem here?
Thomas W
jlw
Rangefinder camera pedant
I don't think the perpendicular-angle problem relates to metering, since the R-D 1 meters via a cell in the camera that "sees" the light bouncing off the shutter blades. The reflection of light off these blades (you'll notice that the two middle ones in the R-D 1 are white) should be very diffuse, and it wouldn't matter at what angle the light arrived originally.
The problem of non-perpendicular rays has more to do with light striking the digital sensor that actually makes the picture, and this could be the source of your problem. However, I use my R-D 1 with a 21mm f/2.8 Avenon (Kobalux) lens, which also is non-retrofocus, and have no trouble with it.
I think there are two possibilities that are more likely:
-- The rear protrusion of your Biogon lens is reaching so far into the camera that it partially blocks the metering cell, leading to inaccurate exposures. In an evenly-lit scene the cell may still be able to see enough to provide a good exposure, but a scene with more extreme lighting variations will be metered incorrectly.
-- Bright light may be bouncing off the camera's CCD sensor, then being reflected off the lens' rear element (which, on the Biogon, is unusually close to the image plane) and then back onto the CCD again. Remember that the CCD, which is covered by a protective glass, is much shinier than the film surface in a film camera. This extra reflected light may be what is wiping out details in the center of your picture area.
I have noticed what I believe to be similar "bounced" effects when using a high-speed lens with a large, nearly flat rear element -- bright edges in the image have a secondary "ghost image" edge next to them, always on the side away from the center of the image.
This effect still seems to be poorly understood, although I have read that manufacturers designing lenses especially for digital cameras now take extra precautions to reduce light reflections off the rear element back toward the sensor.
PS -- I hope you are taking great care that the rear protrusion of the Biogon is in no danger of touching the shutter blades! The R-D 1 uses a metal shutter, rather than the cloth shutter of a traditional Leica M camera, and the extra thickness of the metal shutter may not allow quite as much distance behind the lens mount. I have a Japanese R-D 1 magazine which our RFF friend Mike obtained for me, and an illustration in it appears to show that lenses which protrude more than 20.5mm behind the mounting flange are unsafe to use. (I can't be sure that's what it says because I can't read Japanese!)
With a film camera, it might be possible to make a safety check by locking the shutter open on "B," mounting the lens, and looking through the film gate at the rear to make sure the back of the lens is a safe distance from where the shutter travels. But of course on the R-D 1, there is no way to do this!
The problem of non-perpendicular rays has more to do with light striking the digital sensor that actually makes the picture, and this could be the source of your problem. However, I use my R-D 1 with a 21mm f/2.8 Avenon (Kobalux) lens, which also is non-retrofocus, and have no trouble with it.
I think there are two possibilities that are more likely:
-- The rear protrusion of your Biogon lens is reaching so far into the camera that it partially blocks the metering cell, leading to inaccurate exposures. In an evenly-lit scene the cell may still be able to see enough to provide a good exposure, but a scene with more extreme lighting variations will be metered incorrectly.
-- Bright light may be bouncing off the camera's CCD sensor, then being reflected off the lens' rear element (which, on the Biogon, is unusually close to the image plane) and then back onto the CCD again. Remember that the CCD, which is covered by a protective glass, is much shinier than the film surface in a film camera. This extra reflected light may be what is wiping out details in the center of your picture area.
I have noticed what I believe to be similar "bounced" effects when using a high-speed lens with a large, nearly flat rear element -- bright edges in the image have a secondary "ghost image" edge next to them, always on the side away from the center of the image.
This effect still seems to be poorly understood, although I have read that manufacturers designing lenses especially for digital cameras now take extra precautions to reduce light reflections off the rear element back toward the sensor.
PS -- I hope you are taking great care that the rear protrusion of the Biogon is in no danger of touching the shutter blades! The R-D 1 uses a metal shutter, rather than the cloth shutter of a traditional Leica M camera, and the extra thickness of the metal shutter may not allow quite as much distance behind the lens mount. I have a Japanese R-D 1 magazine which our RFF friend Mike obtained for me, and an illustration in it appears to show that lenses which protrude more than 20.5mm behind the mounting flange are unsafe to use. (I can't be sure that's what it says because I can't read Japanese!)
With a film camera, it might be possible to make a safety check by locking the shutter open on "B," mounting the lens, and looking through the film gate at the rear to make sure the back of the lens is a safe distance from where the shutter travels. But of course on the R-D 1, there is no way to do this!
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jlw
Rangefinder camera pedant
Speaking of odd lenses on the R-D 1...
This evening I was rearranging stuff in my camera cabinet when I got the wild hair to see if my 50mm f/0.95 Canon lens would physically fit on my R-D 1 body.
This lens, as most of you know, is NOT a screw mount -- it has a special rear breech lock ring that works only with the external bayonet flange on Canon 7 and 7s camera bodies. So, I just carefully inserted the lens' rear safety prongs inside the R-D 1's lens mount and held it in place.
Whaddaya know, it fit. Even more surprising, it didn't block the rangefinder window, and since the R-D 1 has a 1.53x "crop factor," it doesn't even block much of the 50mm frameline.
Well, since I was holding the lens on body, I figured I might as well snap off a frame or two (disregarding the good advice I gave in my previous answer!) just to see what would happen. I knew that the back spacing would be off, so the rangefinder couldn't be expected to focus correctly, but I lined it up anyway on a very uninspiring target (the timer dial on my oven) and clicked off a frame.
And take a look -- it doesn't look too bad! (see cropped section inset.) If I actually had been able to focus correctly, it might have looked pretty sharp... who knows?
Drat, now my curiosity is piqued and I'll be feeling the temptation to spend a ludicrous amount of bucks for one of the M-mount-adapted 50/0.95s that occasionally turn up on eBay...
This evening I was rearranging stuff in my camera cabinet when I got the wild hair to see if my 50mm f/0.95 Canon lens would physically fit on my R-D 1 body.
This lens, as most of you know, is NOT a screw mount -- it has a special rear breech lock ring that works only with the external bayonet flange on Canon 7 and 7s camera bodies. So, I just carefully inserted the lens' rear safety prongs inside the R-D 1's lens mount and held it in place.
Whaddaya know, it fit. Even more surprising, it didn't block the rangefinder window, and since the R-D 1 has a 1.53x "crop factor," it doesn't even block much of the 50mm frameline.
Well, since I was holding the lens on body, I figured I might as well snap off a frame or two (disregarding the good advice I gave in my previous answer!) just to see what would happen. I knew that the back spacing would be off, so the rangefinder couldn't be expected to focus correctly, but I lined it up anyway on a very uninspiring target (the timer dial on my oven) and clicked off a frame.
And take a look -- it doesn't look too bad! (see cropped section inset.) If I actually had been able to focus correctly, it might have looked pretty sharp... who knows?
Drat, now my curiosity is piqued and I'll be feeling the temptation to spend a ludicrous amount of bucks for one of the M-mount-adapted 50/0.95s that occasionally turn up on eBay...
Thomas W
Member
Many thanks for your observations and suggestions. My friend used the Biogon on his Konica Hexar RF, apparently with no problem. I wonder if the flange distance is different in the Epson and the Hexar, both M-mount bodies.
Thomas W
Thomas W
Thomas W
Member
I took the advice, and checked the distance from the rear portion of the Biogon to the mounting flange. It is about 20mm. I was also apprehensive about installiing the lens on the R-D1, but I did some rough estimation, and thought that it would touch the shutter curtains.
Thomas W
Thomas W
pfogle
Well-known
As you probably are aware, Epson specify a maximum extension into the camera body of 20.5mm. Some lenses, notably the Jupiter-12 35/2.8 appear to be too long to use, but with the M adapter fitted, they just clear the flange that holds the shutter assembly. (That's on hearsay - I've never tried it myself)
As the back of the Jupiter has a large rear element close to the film plane, it might be worth asking if users of those lenses also have metering problems. I haven't heard of any. Also, if the back of the lens was blocking the meter, wouldn't you expect incorrect exposures all the time, not just with light sources in the picture?
All in all, it does sound as though you're getting a reflection off the rear element. The trouble would be the shiny surface of the IR filter, I imagine, something that you don't have to worry about in a film camera!
Phil
As the back of the Jupiter has a large rear element close to the film plane, it might be worth asking if users of those lenses also have metering problems. I haven't heard of any. Also, if the back of the lens was blocking the meter, wouldn't you expect incorrect exposures all the time, not just with light sources in the picture?
All in all, it does sound as though you're getting a reflection off the rear element. The trouble would be the shiny surface of the IR filter, I imagine, something that you don't have to worry about in a film camera!
Phil
R
RML
Guest
pfogle said:
I have tried the J-12 with adapter on the R-D1 and it works.
I haven't experienced any metering problems.
My J-12 flares badly, though, but that can't be attributed to being mounted on the R-D1 as it flares badly on my FED-2/Zorki 4 as well.