Modifying wire frame finder

[ronald lamarsh]

Some one please tell me if my assumption is wrong: I have a Linhof wire frame sports finder, the kind that fits into the accessory shoe, so it is spec'ed for a 240mm or 150mm lens with 4x5 format. It has to separate frames one for each focal length. I have a 180mm lens I like very much so here's the question: since the difference between 240 and 150 is 90 can I just close off(tape) a portion of the 150mm frame at is equal to 1/3 the distance between the 240mm and 150mm frames or am I dealing with a non-linear function?

[John Kasaian]

Ron,

I don't have a Linhof but the sports (wire) finders on my Graphics are approximations at best. For handheld I just center what I want to capture(is that the word?) in the center of the finder and fire away. If the composition takes the entire frame, thats fine but if I want to crop a tight composition I find that using the gg does a better job. Maybe the Linhofs are more precise, but consider that unless you're spot on viewing through the rear aperture(which itself could be out of wack) the chances of lning up borders exactly with what you'll get on film is a dicey proposition at best. YMMV.

[Leonard Evens]

If your eye is at the same viewing position, the dimensions of the frame for 180 mm should be 150/180 = 5/6 of the dimensions of the frame for 150 mm. You should cut off 1/6 in each dimension, but since you want it centered, 1/12 from each edge should be masked off.