Weird jupiter 8

[Mike Fish]

The RF should agree with the actual distances at both ends of the scale. For the 1m target, measure from the film plane not the front of the lens.

Is this true?

I thought the goal was that the image at the film plane (using ground glass, scotch tape, etc.) was in focus when the RF patch indicated in focus, at both infinity and 1m. And the distance markings were of lesser importance. Obviously it would preferable that the RF patch, focus at the film plane, and distance marking all lined up, but that the focus was the thing.

Meaning focus RF on a very distant target (like the moon) and then check the focus at the film plane. And then repeat with an target at 1 meter. And also check that the lens doesn't focus past infinity - though that would be better than not actually reaching infinity.

(I'm honestly asking. Not trying to be a jerk.)

-mike

thanks

 

[wolves3012]

Is this true?

I thought the goal was that the image at the film plane (using ground glass, scotch tape, etc.) was in focus when the RF patch indicated in focus, at both infinity and 1m. And the distance markings were of lesser importance. Obviously it would preferable that the RF patch, focus at the film plane, and distance marking all lined up, but that the focus was the thing.

Meaning focus RF on a very distant target (like the moon) and then check the focus at the film plane. And then repeat with an target at 1 meter. And also check that the lens doesn't focus past infinity - though that would be better than not actually reaching infinity.

(I'm honestly asking. Not trying to be a jerk.)

-mike

thanks

Sort of - yes and no. You're correct that all three should agree. You're correct that the important two are the RF and actual focus, the scale being more of an indictaion than an absolute. However, the RF is coupled to the lens cam, which in turn is coupled to the scale - all mechanical stuff. If they agree and the RF calibrates to the scale but the focus is not in agreement, then the lens shimming is out; it's the only adjustment available. Furthermore, it's possible for the RF to be out in such a way that correct focus is achieved at some RF distances but not all, if the shimming is also incorrect.

 

[David Hughes]

FWIW, I always check the infinity focussing with a TV aerial some distance away. (I believe they are called something else in other countries.) The point about the TV aerial is that they have well defined horizontal and vertical parts (especially as you are looking at them against the sky) and there's always one a good distance away to check the RF. And they are cheaper than an artificial star...

Regards, David

PS Another way round the problem is to avoid shooting at a metre range and f/2 at the same time but many see that as cheating.