Does Minor Vertical Misalignment Really Matter ?

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Thanks to Bert Keuken, we lucky users have his webpage showing us (very clearly) how to safely access the horizontal alignment screw of the Leica M4/M6.

http://home.wanadoo.nl/bkkn/

Now, if the vertical alignment of the rangefinder patch image is off a little bit, does it really affect focusing accuracy?

It would seem not, because the Leica has a strictly horizontally displaced rangefinder window, but can anyone verify that this is actually true?

If not, it would seem that the most that most users would have to do is to adjust the infinity horizontal setting, and also the rangefinder at some intermediate distances to make sure the calibration of the patch movement with distance is correct.

Anybody have light to shed?

-- Mani Sitaraman (bindumani@pacific.net.sg), December 03, 2001

Answers

If the vertical alignment is off you can still focus accurately. It is annoying as h*** though and critical focus takes longer as the two images never "snap" together as they do with a properly adjusted rangefinder. It is a very simple adjustment on a M3 to early M4-2 camera. You just unscrew the access plug directly above the lens mount and use a small screw driver to make the adjustment. On late M4-2 and up cameras (on M6 and up you have to remove the "red dot"), you need a special tool.

-- John Collier (jbcollier@powersurfr.com), December 03, 2001.

Maybe this LINK helps.

-- Gerry Widen (gwiden@alliancepartners.org), December 03, 2001.

The older M series cameras had a very easy access to adjust the vertical alignment, a screw right in the front of the camera. I played around with my older M3 (a guinea pig for maintenance practice), and it was easy to adjust with a jeweler's screw drive through the hole created from removing the screw.

The M6 requires a special tool, and the removal (and replacement) of the red Leica sticker as opposed to a simple screw. In 1994 Popular Photography magazine did a tear down of a new M6 comparing and contrasting the camera to an old M2, and the vertical alignment adjustment on the M6 was mentioned as having less precise adjustability than the older camera. There were a couple of other money saving things on the M6 that made the M2 look pretty good, but those are not the point of this thread.

The bottom line is that I have been using an old M6 with a slight vertical miss-alignment, and even with my 90mm lenses used at full aperture in the close-up range, focus is as sure as my M6 with perfect alignment. I usually focus by seeking out a vertical line and merging them, so as long as the horizontal alignment is good, the focus is good.

-- Al Smith (smith58@msn.com), December 03, 2001.


Actually, vertical misalignment can have a mild-to-serious effect on focusing accuracy if you focus on something that isn't perfectly vertical (randomly angled tree branch, e.g. or curved feature on face, etc.,etc.)

BECAUSE - you will be 'aligning' parts of the object that are not 'level' with each other.

Think of a very large cap. letter "N". Focusing in the uprights of the N, you will be correctly focused. But if you now point the RF at the diagonal bar, you will see a double image (because of the vertical misalignment). Had you focused on the bar in the first place, IT would have been aligned, but not the uprights (indicating mis-focus).

Since there are very few things in the real world that are 'perfectly' vertical - vertical misalignment is very likely to cause some misfocus most of the time. It may be within the margin of error for most wideangles, but a real problem with a tele.

The work-around is to find a POINT (e.g. a bump on that branch, or the point where the N's diagonal meets the upright) and focus until the two images of that point are aligned one above the other.

Do some experiments with your RF and you'll see what I mean - esp. if it's misaligned(!!).

-- Andy Piper (apidens@denver.infi.net), December 03, 2001.


I was finding this annoying on my old III, but this page shows how to fix it. http://www.mediakyoto.com/camerashopper/lrc_e/index_e.html It's actually really easy, only took a minute. Ray

-- Ray Hyland (ray.hyland@ogilvy.com), January 03, 2002.


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