FoCal Lens Distance Question(s)

[Bill_in_WA]

Math error. 100x50/25.4 = 197" = 16' 5". Same distance for FF and 1.6x.

I've tested at 25x and 50x for lenses from 16mm to 200mm on a 7D and a 5DII.

I posted the results on another thread here in pieces, but I summarized everything, including factors leading to the AFMA choices I made from the data, here:

http://www.canonrumors.com/forum/ind....html#msg61329

Oops, as I said Senior Moment, managed to leave out the 1 on the 198!!!

Just read your write-up and it answers just about all my questions as well as giving me an idea of the various settings on the zooms. It will be interesting to compare the results of the same model lenses on the same model cameras. The only one not common is my 50mm f/1.4.

Like you the 70/200 is about the longest reach I can go to indoors... The 100/400 will have to wait unless I can convince the art store in town to let me use some floor space after hours (The lighting would also be good).

If you happen to have and calibrate a 100/400 I would be interested in your results.

Thanks again for the assistance.

[ChadS]

Like you the 70/200 is about the longest reach I can go to indoors... The 100/400 will have to wait unless I can convince the art store in town to let me use some floor space after hours (The lighting would also be good).

Ever been to an eye exam where the chart is projected off a couple of mirrors in a Z configuration before you see it? There's absolutely nothing that says you can't do the same thing. If you have access to optical-grade front surface mirrors obviously use them. However, any mirror that you can look into and see a 'normal image' as opposed to a warped, 'fun house' image will work just fine. Be sure the mirrors cover the maximal rays that will enter the pupil of your lens (lines from the edges of the target to the outside edge of the front glass). The partial reflections you'll get off the glass should have nearly no effect at the working distances you're discussing.