How to adjust infinity on IIIg rangefinder?

[ironringer]

Advertisement (gone after registration)

Could experienced "adjusters" tell me how to adjust the IIIg rangefinder for correct focus when the lens is set at infinity distance? I was told that removing the front cover screw beside the rangefinder window reveals an adjusting screw needing a 1.2mm flat blade. Then, I believe, the process is to set the lens at infinity distance, look through the rangefinder at an object a mile away, and adjust the screw to merge the rangefinder images. Please confirm IF that is the procedure, or otherwise correct me.

Is that adjusting screw tight, or relatively easy to turn?

[payasam]

I have never even held a IIIg, but the procedure you describe is the same as that used with the IIIc and earlier Leicas. The screw is relatively easy to turn although it would not hold its setting if it was loose.

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[120]

Ironringer, let us know how it goes...

[spydrxx]

Never used a IIIG, but have several other screwmount variants. In addition to what you mentioned, I was advised also to remove the rangefinder cover ring on the shutter speed selector on the front side of the body, as it apparently contains either a prism lens (some models) or affects an internal vertical mirror adjustment (other models). It is the dual interaction of the vertical and horizontal adjustments which achieves perfect infinity focus. Typically the adjustment is made with a small caliper rotating the window. I check my gear seasonally about twice a year, as I've found that the adjustments are very sensitive to any impact (such as flopping against my body while hiking, or even geting jarred in the car on rough roads. It isn't rocket science, but the end result makes fine focusing much easier.