Topic: Rangefinder mis-alignment

[choppert]

A couple of weekends ago I spent a rather blurry night at the ERC finals in Cardiff. 
During which I believe I conducted a couple of gravity inspired robustness tests of my Canon P rangefinder! 

Now, two days before hols, I've noticed a slight focussing problem!
There are some trees about three miles away that when I focus on them and then look at the barrel of my lens the lens thinks they are between 5 and 6 feet away!   

Clearly the camera needs looking at when I get back (I assume there's something wrong with the RF alignment or the cam in the camera lens mount?)

My question - I should be ok to use the camera and scale focus (assuming my drunkenness didn't damage the lens as well!)?

Chops

[Pete_R]

You should be OK with scale focussing.

Do you have another lens to try? That would prove it's the body not the lens.

[Francois]

You can always try it with a piece of vellum as a groundglass.

All rangefinders have an adjustment screw somewhere inside...

I also found this

Rangefinder Calibration

It's very easy to knock rangefinder cameras like the Canon P out of horizontal or vertical RF calibration with small knocks or jars. This is fairly common on older (and even newer) rangefinders. Thankfully, Canon provided for a way to adjust both horizontal and vertical RF calibration without opening the camera up. I asked the question on the RF list and Harland Harris and Jim Williams were kind enough to provide the answers:

    The external adjustment is behind the large screw in the lower corner of the front viewfinder window. The outer screw is just a decorative cover; the actual adjustment is inside. It takes a VERY tiny screwdriver. The adjusting screw moves in and out as you focus the lens, so you may find it's easier to reach at either the infinity position or the close focus position, depending on your particular screwdriver.
    Before you adjust it, check the vertical adjustment -- on a P (as with other V/VI - series Canons, and old Leicas) changing the vertical adjustment affects the horizontal adjustment, so if the vertical adjustment is off, it will affect the horizontal adjustment too. I find the vertical adjustment seems somewhat more likely to get knocked out of whack.
    This is adjusted in the traditional Leica fashion by removing the knurled decor ring around the round rangefinder window, and turning the round glass front. This is actually a shallow prism and moves the RF image in a circle as you turn it. After you've adjusted it, you have to check the horizontal adjustment and reset it if necessary.
    -- Jim Williams

    Note: This operation while simple, has the possibility of fouling your camera if you have the wrong size screwdrivers or slip while the driver is inside the camera. Please use reasonable and appropriate caution when thinking about doing this.

They also have the name of a repairman on the page
http://www.photoethnography.com/ClassicCameras/CanonP.html

[choppert]

Bizarrely, after a week of scale focussing I went to use the P earlier and the rangefinder works fine.

Even measured it with a tape measure!

Any idea what could cause intermittent rangefinder mis-alignment?


Chops

[Pete_R]

Best guess is the cam follower got caught up on the edge of the lens focussing cam when it got knocked. Removing the lens of just focussing down to minimum distance could have got it to drop back into place.