It is not uncommon for old rangefinders to have rather bleak rangefinder patches. The Aires mentioned before on this blog was, for example, hardly useable unless in very bright conditions.
But help is available. I am embarrassed it is not a trick of my own invention: Place a small piece of black tape on the camera front! Soooo simple, yet soooo effective.
The trick is to make the piece of tape the same size as the rangefinder patch which of smaller than one imagines:
The rangefinder updated with a small piece of black tape.
The effect is to increase the contrast between the “straight-through” and the projected images. If the tape is of exactly the correct size it really does wonders!