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Re: Eclair Cameras: Lens testing procedures
Speaking of newspapers, another still photographer trick is to draw a line
vertically on a page of newsprint, place it on a wall and then shoot this
at a 45 degree angle to the wall. Focus on the vertical line with the
viewfinder and then later see if the line is in best focus or the type
which is more near or more far away than the line. This determines if the
viewfinder focus is the same as film plane focus. You can also use a tape
measure to set focus and see if that's where focus truly lies.
A nice piece of optical equipment is the lens projector. One could be made
from a slide projector. The slide is an almost perfect resolution pattern
and the correct lens mount would have to be installed on the projector to
take the lenses. An old SLR camera body could hold the lens and slide if
you are testing SLR lenses. The image is projected on a screen in a dark
room. Resolution, color fringing and other defects are shown on the
screen. Instead of photographing a large test chart and then trying to
analyze a little piece of film, the film starts out near perfect and the
imperfect image the lens produces is magnified for inspection on the wall.
C.J.
I'm going to be shooting some lens tests soon and was wondering if
anyone could suggest some procedures. Is there a standardized resolution
chart I can use to evaluate sharpness and contrast? In the past, I've
done some informal tests by taping newspapers to a wall, but I'd like to
get serious this time. Will telecined footage be sufficient to evaluate
performance or do I have to project the film (I don't own a projector).
Any tips or tricks would be appreciated.
- Ian Marks
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