Re: Alignment problems...

[P3D John Bercovitz <bercov@xxxxxxxxxxx>]

> Situation #1 is the most severe.  Difference in size in the y-direction
> causes vertical misalignment.  If the two chips are aligned at the bottom
> then the misalignment gets worse as we move to the top.  Best strategy to
> minimize bad effects of misalignment is to align the image at the center. 
> Both bottom and top will be off a bit but eyestrain will be minimized.
> 
> Question:  What causes this?  Is it a difference in focal length or a
> difference in the distance of each lens from the film plane?  Can it be
> fixed?  In prints or during slide duplication one could correct by changing
> the magnification of each copy.  But can it fixed in the camera?  If, using
> shims, we change the distance of the lens from the focal plane then we can
> match the sizes.  Both images will not be in focus at once but at small
> apertures this might not be noticeable.  Is this a valid approach? 

I think Ed Romney answered this one yesterday.  You shim the lens to the 
right distance and then shim the front lens of the triplet to change its
focal length to bring it back into focus.  This would be an iterative
process, I believe.  Hmm...  No, both of those shims would pull the image 
to the front.  OK, so you may have to shim the left and right lenses both.

John B


------------------------------