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...
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