Re: Picking a Mark IV Lens

[Chris Albertson <chrisa@wavenet.com>]

Herbert R Johnson wrote:

> able to tell you right off.) Finer measures would require some effort
> to build a camera that would expose film across the entire width of
> the image field (I believe a standard 35 mm camera would not be wide
> enough.)

Herb, you read my last post before I posted it.  I was about to
suggest
using a 35mm camera and transfer to Kodak Photo CD.  

I think the diagonal of a 35mm frame (36 x 24 mm) is about 1mm
_larger_
then the CCD.  I think the chip is 30mm square.  So if you plot
the density along the diagonal of a 35mm frame you will get the light
fall off v. radius data you need.

I do like your daylight projection idea.   It is quick and simpler.
Get a light meter and
cover the sensor with a pin hole.  Take reading along the radius
line.  My Minolta meter reads to 1/10 f-stop.  This is not so good as
a 12 bit scanner but would catch a problem.

If you did want to measure the whole image circle you could use a
view camera.  This would be easyer then making one.  An old "thrasher"
speed graphic would be perfect.  They sell for $200 and have a 4x5
inch
focal plane shutter.  I'd just go with the 35mm camera.

-- 
   --Chris Albertson             home: chrisa@wavenet.com           
     Redondo Beach, California   work: chris@topdog.logicon.com