Yashica GTN rangefinder adjustment

[Eugen Mezei]

Hello!

After my first roll in the GTN I constated that it focuses to close (the final image is focused in front of the subject when the rangefinder was on the subject).
Checking on the moon indeed it shows that the rangefinder image lines up between the 6m and infinity marking of the lens. Almost touching the inf. mark but I can focus the lens further to the middle part (where the two circles of the 8 came in touch) of this sign. Interestingly the two images of the moon in the rangefinder remain covered, the yellow part doesn't move further.

I looked at http://www.yashica-guy.com/document/repair.html#six and intend to do the adjustment. Just some questions:
- does it suffice to have the rangefinder adjusted to infinity or should I check for other distances (especially the close ones at 0,8.... 1 ... 2m)?
- for infinity: I focus as long at is goes no further (mark aligns nicely exactly at the middle of the inf. sign) and I can be shure that the lens is focalised correcty or should I check with a splitscreen in the film plane?
- I removed the dust protection in the hotshoe and now I see very deep in a silvery screw. Is this the one I need for adjusting the rangefinder? It seems to me to bee very deep in the body, almost under the rangefinder. Just to be shure and don't mix it up wiht some other adjustment.

Greetings,

Eugen

 

[sevo]

Adjust the rangefinder and make a test film first. Rangefinders are so much a known point of failure that they all have user accessible adjustment screws - lenses haven't, which reflects the likelyhood of them developing a purely focus problem.

Besides, there are many traps and pitfalls when it comes to adjusting lens focus, most of all the need to match the film plane to within fractions of a millimeter - which makes your first do-it-yourself lens adjustments a process with quite a few trial and error iterations. As long as you don't know it is the lens which is at fault, you should not attempt to fix it, at any rate not until you have worked out a reliable test procedure.

The adjustment screw is indeed quite deep in, and inserting a screwdriver from the hole in the hotshoe tends to obscure the rangefinder spot - I prefer to remove the top for adjustments.

 

[martin-f5]

if you have to adjust the rangefinder it's realy like sevo had described it.

But I do something more, I use a matscreen (ground-glass plate) from my Leica SLR and lay it on the filmside.
I open the backside and focus on a subject in 1m distance,
i controll that with a magnifying glass 10x on the ground-glass plate.

For me it's importand to have the best focus on 1m for portraits.