M7 - perfect vertical calibration at infinity, but not at close focus?

[Jon Warwick]

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Vertical alignment looks perfect at infinity.

BUT ...vertical alignment is incorrect at the close focus range for head portraits, ie, the eyeball in the rangefinder patch is very slightly higher than where it should be.

This makes precise focus on the eyeball harder because (even with a slight misalignment) the image through the viewfinder never sharply "snaps" into view!

How is it possible that Vertical calibration is perfect at infinity ....but not close up?

I only have 1 lens so haven't tested with another lens, but presumably it's rangefinder calibration that can only cause this problem, and not a specific lens?

Also is there a DIY fix to this on the M7, or really something only for an expert ....I'm already wondering how adjusting the Vertical for close-up won't throw off the perfect alignment at infinity?

 

Edited August 1, 2021 by Jon Warwick

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[Ecar]

These threads should get you started:

https://www.l-camera-forum.com/topic/118043-m9-coincidence-at-infinity/

https://www.l-camera-forum.com/topic/302810-vertical-diy-rangefinder-adjustment/

[Jon Warwick]

15 minutes ago, Ecar said:

These threads should get you started:

https://www.l-camera-forum.com/topic/118043-m9-coincidence-at-infinity/

https://www.l-camera-forum.com/topic/302810-vertical-diy-rangefinder-adjustment/

Fantastic. Many thanks.  

An initial read of both articles (the first one with the hand-drawn graphs is mesmerising!) suggests, knowing me, that I could end up messing up my rangefinder accuracy more than it already is. Given it focuses accurately and prints are tack sharp, I might hold off and add the adjustment to the lengthening list of things that now need CLA'ing on my M7 whenever i finally send it to Germany after nearly 20 years of ownership.  For now it's just a bit disconcerting that when I get the pupil correctly aligned horizontally, I can see a 1/4 of an "extra" pupil above it!

Anyhow, many thanks again for your help.