framing differences between AV1 and A1/F1greenspun.com : LUSENET : Canon FD : One Thread
The AV-1 only shows about 85% of the total picture. After carefully composing and cropping a photograph, this unwanted detail is, to say the least, annoying. Do all FD series cameras have this drawback, or do certain models show a true (for want of a better word/acronym) WYSIWYG?
-- Matt Chambers (email@example.com), July 23, 2001
Matt, the A-1 manual specifies 93.4% vertical and 95.3% horizontal coverage. Over the years, I've had a few instances where a tiny sliver of unwanted image appeared in the slide, but for the most part, it has been WYSIWYG for me.
-- Alan Swartz (firstname.lastname@example.org), July 23, 2001.
I don't have the exact figures handy but the professional F-1 bodies (old & new) have the greatest viewfinder coverage. If memory serves me they weren't quite 100% but were at least 98%. A-1s & T90s were in the low 90% range.
One technical reason for the reduced coverage is that the lens register distance (the distance from the back of the lens to the film plane) on Canon FD is about 42 mm - almost the shortest in the industry. This makes it more difficult to put in a mirror large enought to cover the entire frame.
Another reason is simply to save money. Since most prints are (or were) cropped anyway and slide frame openings were smaller than 24 * 36 mm the designers felt they could use a smaller mirror & pentaprism.
-- Duane K (email@example.com), July 24, 2001.