camera shows, some repair data

[P3D romney <romney@xxxxxxxxxxxxxxx>]

>Date: Tue, 12 Nov 1996 13:18:18 -0500
>To:photo3d@xxxxxxxxxxxxxxx
>From:romney@xxxxxxxxxxxxxxx (romney)
>Subject:camera shows,+ misc
>
>Thanks Allan for praise. I'll be at Spartanburg show 16Nov, Charlotte
>17Nov and Minnereg/ Tampa/Largo former Reinthaler show in early Feb with
>camera repair data, etc.
   To check focus our old time "trade secret" trick was to make a straight
line in a field of grass with a white string or lime chalk powder. Stand
about 15ft away with camera back parallel to the line and photograph it
using the RF to set distance. If the grass blades are sharper ahead or
behind the line at any point something is definitely wrong. WHAT is wrong
is rather a complicated story to explain here. To check film plane and
curvature  right out to the corners you hold the camera diagonally. You
need a 10x or greater power loupe to see the slide with this test. Good
thing to own! Stereo viewers  are not powerful enough for this work. Now
,,,to check if your lenses are different focal length (which is rare) you
get a reticule magnifier from Edmunds Scientific or someone and measure the
size of the two images on the slide. My reticule reads to 0.005 inch. If
the images are different size the two lenses have different focal lenth.
You can adjust the FL of a triplet you know by changing the spacing of the
front element. It can make changes as much as  5%. This is how simple
cameras with rotating front elements focus you know. But be VERY careful
and read up on more optics before trying this. And if you shoot handheld at
less that 1/150 sec, that is probably your real trouble. Use a tripod!
Gotta go..used too much bandwidth already ...ED Romney
>



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