J8 Problem

[rolleistef]

Hello all,
I've printed my latest Kiev production and once again it's copletely soft with no detail and no sharpness even at f11 or 16. I've re-collimated the lens once again but screwing and unscrewing the lens element inside the block, till it got sharp enough on the focusing screen of my rolleiflex (usual collimating method : put the lens at infinity, put it on another lens you know is good, check on 2nd camera VF etc; on a rolleiflex it's much more confortable to look). I then compared the results with another camera : it was way too soft compared to the J8 on my Zorki 4. Do you think it might be the camera that is in fault? (working distance?) Could I have harmed the lens so much that it cannot be easily fixed? Waiting for your answer before ordering a new one at Oleg's and spending 14€ (shipping included). (Oh and if you ever have several J8 or H103 you want to give away, I'm ready for adoption!)
stef

 

[januaryman]

Add my name to that adoption list, folks! I'll give any free lens a good home and proper care! ;D

 

[Spyderman]

rolleistef: do you check your lenses only on infinity focus ? Do you check also at 1m at film plane ? Are you sure the other camera's infinity IS INFINITY ? (not just sure, but is it proved?)

 

[rolleistef]

yes i'm testing it at infinity, but not 1m. For the other camera's infinity, yes i'm pretty sure it's infinity. What does it change to check at 1m? How do we do that? Do we have to focus the other camera at 1m?
thanks for your kind help 🙂

 

[Spyderman]

What does it change to check at 1m?

That's simple: by checking at infinity AND at 1m you make sure the actual focal length of the lens matches the focal length supposed by the designer of the rangefinder.

For example the so-much-talked-about incompatibility of FSU lenses vs. Leica bodies: it's because of as small difference as 0.7mm in actual and supposed focal length!

A totally crazy idea: it would be possible to mount a 35mm optics in J-8 barrell and make it focus correctly at infinity. One would think it would even take pictures. But as you try to focus the lens closer from infinity, the focus would be further and further from where you want it to be.

How do we do that?

Use either a focussing screen from a SLR, or a piece of ground glass on the film plane, shutter open on B, target at 1m from film plane...

 

[rolleistef]

thanks a lot for you help! I'll let you know!
Stéphane