[pure-silver] Re: Light source vignette or hopefully avoiding it


----- Original Message ----- From: "Frank Filippone" <red735i@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, July 14, 2006 3:36 PM
Subject: [pure-silver] Re: Light source vignette or hopefully avoiding it


What Richard said......

Frank Filippone
red735i@xxxxxxxxxxxxx


Is there any way to figure this out?


Could I draw the cone of light the image forms? Using the formulas for focus
to define the triangles? That makes sense doesn't it? It's then a simple math
problem. At least if I looking at the problem correctly.

Nick

The angle of interest is the angle between the lens and the film. You can calculate this from the formula for lens to film focus distance. This distance should be the maximum you think you will ever use since that is the narrowest angle. By plotting a triangle with the lens as the apex and the film as the base you can measure the angle graphically or, for that matter, find the place where the distance across the triangle (forgot the term) is the opening in the enlarger. You can measure the equivalent distances from the lens to this aperture and from the aperture to the film from the graph. One can do this trigenometrically also from the tangent of the angle.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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