Canonet GIII QL17 Rangefinder mask

[thepiecesfit]

Can anyone comment on the alignment screw for the rangefinder metal mask in the front of the camera left of the eyepiece? Not the one in the back or through the top for actual viewfinder focus. The reason I ask it seems to have a screw there that keeps rotating without end. It seems to put more pressure and less pressure on the mask that slides up and down as you focus. I just don't know the optimal position of it. Its a bit lopsided and I feel like not completely secure. The image does align in the viewfinder though.

I did a calibration through the lens and the other screws but want to make sure I didn't miss anything here. Picture attached is something I found online. Circled to show which screw I'm speaking about.

 

[thepiecesfit]

As a followup this image shows the screw orientation and how it impacts the height of the mask. I cannot find anything on the correct orientation of this screw. Can anyone comment on what the factory 'default' is?

 

[Ranchu]

I think the only way to adjust this is to put the camera on a tripod, put a ground glass/focusing screen on the film rails, and adjust it until the view in the finder matches the view on the ground glass. I think it's usually at minimum focus. You could prbably use wax paper instead of a ground glass, since it isn't critical focusing.

 

[thepiecesfit]

I think the only way to adjust this is to put the camera on a tripod, put a ground glass/focusing screen on the film rails, and adjust it until the view in the finder matches the view on the ground glass. I think it's usually at minimum focus. You could prbably use wax paper instead of a ground glass, since it isn't critical focusing.

I used a piece of scotch tape to calibrate focus on the film plane using the vertical and horizontal screws and a loupe. The mask position screw doesn't seem to impact minimum focus distance but more of the longer range double image in the viewfinder. I can get minimum focus down no matter where the position is.

The problem is despite being focused at minimum distance it still gave me issues past 15 feet, seeing a double image. Adjusting this front screw of the mask fixed my double image past 15 feet. I'm not certain its correct. I suppose I would have to check with the loupe for the longer range as well. But it would help to have a picture of someone's front screw that is in the correct position.

 

[Ranchu]

I'm just assuming the screw adjusts the mask, which is intended to show what will wind up on the film. The waxed paper (or use tape) is just so you can see if the corners of the mask line up with where the corners are on film (the film gate), when you look through the finder. The focus will be a different adjustment..

 

[Sid836]

I would clean up the rangefinder adjustment path with some lighter fluid on a thin brush. It might be that the path and the pin are dirty and they not move following smoothly the lens.