Spyderman
Well-known
Hi,
just finished a little experiment and wanted to share my results...
Test conditions:
I put my Bessa R2 on tripod with film plane exactly X from target on a wall. I tried to focus the lenses using RF and then using a focussing screen with split circle on the film plane.
I tested 3 Jupiter-8s and 2 Jupiter-9s. All lenses had been collimated at infinity using "2 cameras with facing lenses collimation"
The results:
All Jupiter-8s focussed on focussing screen according to the scale on lens - The target was sharp when scale showed 1m or within the DOF at f/2. When I focussed the lens using RF - the scale showed about 1.05m (the 1m was lined up with the left f/4 DOF line).
In other words: with Leica calibrated RF all these lenses would back focus by about 5 cm or 2 inches.
One Jupiter-9 (silver - '55 - newly acquired) focussed on the focussing screen exactly as on the scale (checked at 1.3m).
The other one (black - '80 - my main user) focussed the target (1.3m far) on the focussing screen when the scale showed 1.25m (5cm front focussing relative to the scale).
When I focussed both lenses by RF, the scale showed 1.4m on both.
In other words: with Leica calibrated RF the silver one would back focus by 10cm and the black one 15cm!
I even checked the camera body with my CV 35/2.5 and the RF as well as focussing screen focussed the target at exactly 1m.
Dante Stella reached similar results in his article here (click).
PS: seems I'll have to do something with my black J-9...
just finished a little experiment and wanted to share my results...
Test conditions:
I put my Bessa R2 on tripod with film plane exactly X from target on a wall. I tried to focus the lenses using RF and then using a focussing screen with split circle on the film plane.
I tested 3 Jupiter-8s and 2 Jupiter-9s. All lenses had been collimated at infinity using "2 cameras with facing lenses collimation"
The results:
All Jupiter-8s focussed on focussing screen according to the scale on lens - The target was sharp when scale showed 1m or within the DOF at f/2. When I focussed the lens using RF - the scale showed about 1.05m (the 1m was lined up with the left f/4 DOF line).
In other words: with Leica calibrated RF all these lenses would back focus by about 5 cm or 2 inches.
One Jupiter-9 (silver - '55 - newly acquired) focussed on the focussing screen exactly as on the scale (checked at 1.3m).
The other one (black - '80 - my main user) focussed the target (1.3m far) on the focussing screen when the scale showed 1.25m (5cm front focussing relative to the scale).
When I focussed both lenses by RF, the scale showed 1.4m on both.
In other words: with Leica calibrated RF the silver one would back focus by 10cm and the black one 15cm!
I even checked the camera body with my CV 35/2.5 and the RF as well as focussing screen focussed the target at exactly 1m.
Dante Stella reached similar results in his article here (click).
PS: seems I'll have to do something with my black J-9...
Last edited:
Jocko
Off With The Pixies
Ondrej, I was at first very dubious about Dante Stella"s theory, but having carried out similar tests with a dozen or so FSU lenses, I have had very similar results to yours. There are doubtless individual variations, but the evidence invariably suggests that he is right.
I wish he weren't!
All the best, Ian
I wish he weren't!
All the best, Ian
nzeeman
Well-known
it is strange - i never had problems with my lens. i didnt do real tests but i never saw errors on real life photos. maybe im more tolerant to misfocus...
Spyderman
Well-known
You may be right Brian that some FSU lenses are lemons, but as i mentioned: all the lenses in test had been collimated some time ago, but only at infinity. Now I wanted to check the close focus and here are the results...
V
varjag
Guest
Yakovlev in his 1962 repair book made a point of collimating auxiliary lenses. Perhaps it was more of an acknowledgement of real-life variation from production line, while the lenses were still supposedly built to some focal length standard.
Spyderman
Well-known
Kim Coxon
Moderator
Ondrej,
I wouldn't worry too much about the focus scale unless you want to carry a tape measure.
If I read your descriptions correctly, then:
With the J8s, when you use the RF, the actual point of focus is slighty behind the object in the RF. In this case, you will have to remove the rear group and gently remove some metal from the tube it fits into. This will effectively shorten the focal length slightly. You then need to thin the main shims so that the lens focuses at inf. Then check the close focus again. It is a bit trial and error and only remove a small amout at a time.
The J9s can be a bit simpler. The rear group is usually shimed so you can reduce the thickness of these relatively easily. The procsdure is the same then as the J8s. However you may find that with the reduction in the main shims, the aperture ring stops the lens unit from sitting against the reduced main shim. I do these with the aperture ring removed and if this problem does occur, I gently sand a bit off the back of the aperture ring until it fits once the collimation is conplete. Because of the reduction in the main shim, you may find the the aperture scale index mark is way off centre. If so and you can't live with it, you can make a new index mark with the tip of a drill, fill it with red paint and reset the aperture ring.
Kim
I wouldn't worry too much about the focus scale unless you want to carry a tape measure.
If I read your descriptions correctly, then:
With the J8s, when you use the RF, the actual point of focus is slighty behind the object in the RF. In this case, you will have to remove the rear group and gently remove some metal from the tube it fits into. This will effectively shorten the focal length slightly. You then need to thin the main shims so that the lens focuses at inf. Then check the close focus again. It is a bit trial and error and only remove a small amout at a time.
The J9s can be a bit simpler. The rear group is usually shimed so you can reduce the thickness of these relatively easily. The procsdure is the same then as the J8s. However you may find that with the reduction in the main shims, the aperture ring stops the lens unit from sitting against the reduced main shim. I do these with the aperture ring removed and if this problem does occur, I gently sand a bit off the back of the aperture ring until it fits once the collimation is conplete. Because of the reduction in the main shim, you may find the the aperture scale index mark is way off centre. If so and you can't live with it, you can make a new index mark with the tip of a drill, fill it with red paint and reset the aperture ring.
Kim
Spyderman
Well-known
Thanks Kim. This is exactly what I needed to know 
Thanks.
Thanks.Spyderman
Well-known
OK, so I did it (with the black J-9 lens):
- removed the shim under the rear group
- removed the main shim
and now the lens focusses exactly according to the scale. I mean that the lens now focusses the same as the silver one...
The problem is, that the rear group nor the optic module can't be screwed any further - so it can't be adjusted for Leica standard without a lot of filing...
- removed the shim under the rear group
- removed the main shim
and now the lens focusses exactly according to the scale. I mean that the lens now focusses the same as the silver one...
The problem is, that the rear group nor the optic module can't be screwed any further - so it can't be adjusted for Leica standard without a lot of filing...
40oz
...
If it focuses at the film plane and matches the rangefinder, and the distance scale matches a tape measure, what needs further adjustment? Seems to me it is working fine at this point? Sorry if I am I missing something.