How to mask focusing screen for 8x10 format?

I want to mask or mark a focusing screen for the 8x10 format.

 

What sort of marker or other marking implement should I use to ensure it does not rub off? WHich side of the screen?

 

How do I measure the screen to determine where to draw the lines? Camera is a D1H

 

Thanks.

16x24= (8x12) x 2. You want 16x20 area. That is the easy part.

 

There is no home way of doing it in any way you would be proud of.

 

I would contact Katz Eye and see if they can mark it off professionally. They mark off their screens.

If in the future a Nikon D3 is on your shopping list, the D3 has a 5:4 format mode that crops up to 8x10 without a fuss.

what camera are you using?

Is there any way to do that crop precisely to the final image on NX? (I want to mean something like the D300` in-camera cropping feature).

Katz Eye does make an 8 X 10 mask but they don't list a D1H in their on line list. Call Rachel Katz at 413.743.2523. She is the most helpful, professional camera person I have ever dealt with!

I have seen a few focusing screens over the years where people have cut a 1mm-wide strip of Scotch tape with a black line drawn on it with a Sharpie pen, and placed two of these tape strips on either side of the ground glass to mark the 8x10 crop. Your strips will each need to be about 1mm x 15mm. Not elegant, but it certainly works. And, best of all, it's reversible. I would suggest re-doing them every 3-6 months, long before the tape would get gummy.