Focaslide - use as diagnostic tool ?

[Luddite Frank]

I should be able to figure this out on my own, but my brain seems to be on holiday... 😉


I have a Leica"Focaslide" ( which was pimarily intended as a close-focus aid from copying and other close-up work, as I understand it ).

I am wondering if I can also use it to check filters & hoods on various LTM lenses for vignetting or other optical anonalies... ( Instead of wasting film to achieve the same end )... 😉


I think I tried this once before mounting a 5 cm / 3.5 Elmar on the Focaslide, but could not get a sharp image on the ground-glass....

Has anyone tried this idea before ? 😕


Thanks,

Luddite Frank

( PS: I do have the PEGOO (?) focusing magnifier...)

 

[Al Kaplan]

I doubt that you'd be able to see any but the most severe vignetting that way. The eye isn't very good at determining variations in light levels.

 

[John Shriver]

It can be useful for collimating lenses. Se Tomosy's Leica Camera Repair book.

 

[payasam]

To add to what Al said. Vignetting is most pronounced at small apertures, and at those the image on the ground-glass would probably be too dark.