Adding Crop Lines to focus screens

[TedBaker]

I like to work in the 4:5 ratio and I am starting a project using my 35mm cameras.

Ideally I would like to have the edges of the frame just darker, but I would happily settle with two lines that represent the 4:5 ratio.
The screen that I have in mind to start with is K2 screen from a FM2, and if it works well I my try it a screen for the F4.

It seems pretty straight forward to do, but perhaps not?

As this aren't all that easy to replace I would prefer not the ruin them.

[richardHaw]

do not mess around with the screen because adding anything in-between the screens will throw away your focus accuracy 

the easiest way is probably to cut a circle with a squarish 4:5 aperture from an exposed film leader and sandwich it under the eyepiece 

this is easy...next, find a way to mask the aperture of the film gate. You may mask it with a very thin material like foil but it may catch and scratch your film and if you put it on the other side you may ruin your shutter.

just shoot medium format. I love my Bronica 

[pluton]

There is no need to add a physical object to the screen assembly.  Also, shooting through clear photographic film will probably not be satisfactory...because it's not actually very clear at all, depending on the film used. Graphics products might actually be clearer, but carry the same annoyance of statically-attracted dust.
 I suggest you inscribe the necessary lines on the screen using a fine pointed pencil or very fine point marker(extra fine Sharpie in the USA).  Pick any color you want!
If you really need to erase all traces of the inscribed lines later,  a washable water-based marker might clean up more easily than the "permanent" Sharpie ink. 
In the past I did it with a Sharpie and was able to wash off the marks later using methanol.  Of course, handling the focusing screen this much invites permanent scratches and marks. 
Measurement and marking will have to be very precise if you want exact agreement with the framing of the shots on film. 
I advise using a separate 'junk' screen so you can skip the delicate cleaning after use.

[TedBaker]

I only want to mask the finder, that's what I have done in the past, but it was a lot easier on 6x6 SLR.

I thought a sharpie would be much too thick and would run.

I had thought of a craft knife, to scratch it permanently.

[pluton]

If reversability is not needed, then scratching the lines might be the simplest solution.  Don't miscalculate the location of the marks.

[David H. Hartman]

Scribing a line on a K2 screen isn't an easy thing to do. Slips are the norm. I would not try it. A strait edge can easily mark the matte surface the side you'd scribe. To scribe a line on a K2 screen I'd need some sort of jig to hold the screen and a strait edge that almost touches the screen.

A mask might be placed below the screen on an FM2, FE or later as the screens mating surface is above with a spring below. A Hasselblad, Pentax 6x7 and the Nikon F through F5 has the focus screen matting surface below. A mask cannot be between the focus screen matting surface and the screen or focus errors will occur. A mask will be a distance from the focus screen and may not work will in a Nikon F through F5.

I still own several FM2n(s) and FE2(s) and not one has an E2 screen installed. Perhaps I was preparing to sell a couple of FE2(s) and didn't because the price was too low to take the trouble to sell them. Anyway if a split image rangefinder is not needed the E2 or E3 screen might work well and would not require any modification of anything. The E2 screen was my standard screen in the FM2n and FE2.

Nikon FM2(n) - Instruction Manual Part 5
Photography in Malaysia

I'm not sure of the ratio but I think the side lines are pretty close to a 5:4 ratio. Have a look. If so then a E (course for fast lens), E2 or E3 screen will fit any of the FM/FE family that has interchangeable screens. The FM is the only one that doesn't. Exposure compensation or calibration is required for switching between E and E2 screens. Switching between E2 and E3 is not supposed to require meter calibration or compensation.

I hope this helps,

Dave Hartman

[TedBaker]

No the E2 or same one for the F4 don't match 4:5 ratio.

Though I think the ends horizontal lines can be used a guide.

Thanks for the detailed reply, so the $300 price I have seen for custom scribed screen isn't so bad after all...

[David H. Hartman]

Ouch!