Blue cellophane comes standard as a protective cover on your rangefinder’s viewfinder, but the blue cellophane rangefinder trick can also help you!
I’ve known about this trick for many years and thought everyone else did too. But the truth is most people do not, especially those new to photography. If you shoot with a Leica, Voigtlander, Canon, Zeiss, Zorki, Yashica, or Olympus rangefinder, then you’re in luck! Besides doing a CLA (Clean Lube Adjustment), there are better ways to make your rangefinder more visible.