View Full Version : Improve the Rangefinder contrast and visibilty

4-Oct-2012, 12:55
This is one experiment for those that service and work on rangefinders,

Here is a list of beam splitters with different transmitting and reflecting ratios, which one do you think is best? my intent is to improve the rangefinder contrast and visibilty in a old Polaroid 110B camera.

I have no idea which reflectivity and transmission ratio would work best, one or two out four on this list may be suitable,

25mm X 38mm, 30R/70T, Plate Beamsplitter
NT46-667 $39.50
25mm x 38mm, 40R/60T, Plate Beamsplitter
NT46-704 $39.50
25mm X 38mm, 50R/50T, Plate Beamsplitter
NT32-363 $39.50
25mm X 38mm, 70R/30T, Plate Beamsplitter
NT46-669 $39.50

4-Oct-2012, 13:27
I don't know but sign me up when you figure it out. My 900 works fine but I wouldn't say no to even better contrast/visibility!

Also, mine has worked itself out of alignment vertically. Any tips on getting into the RF and fixing that? I unscrewed all the visible screws but still the housing wouldn't come out. I've adjusted RF's before so I'm not just bumbling about, but I don't think it's worth it to send it off for a 1mm vertical alignment issue.

4-Oct-2012, 15:14
Hey Bryan, Email me and I have a tutorial about tuneing your 900, I can send you. it is easy, there are 3 screws got to Come out to get the top off

4-Oct-2012, 19:44
In a traditional rangefinder, any light reflected by the half-silvered mirror means the viewfinder is just so much darker. If you use a 70R-30T, that means you're blocking 70% of the light from reaching the eye, except for whatever patch is being used to focus. You'll end up with a very dark image, difficult to frame, and a blindingly bright focus spot. I suspect factory-installed mirrors are closer to 30R-70T. I would be interested in buying some of those, so far I'm cannibalizing dead cameras when they have clean mirrors but that's not always easy to do without damaging the mirror. I've never tried a Polaroid, but I do this from time to time on strange cameras from the 30s-60s. I would change the mirror on my Ferrania Condor I if I had a supply of new mirrors that I could cut to size.