[pure-silver] Re: Optical question

From: "Peter De Smidt" <pdesmidt@xxxxxxx>
Suppose one were to put a piece of 5mm thick acrylic between a negative and an enlarging lens. Would the piece of acrylic cause the distance needed to focus the negative at a given size to change? 

Yes.
If so, would there need to be more or less extension between the negative and the lens? 

More ... the negative will appear 'closer' to the lens and
so you will need to move the lens farther away to compensate.

With thin filters, and distant objects, there is less focusing
offset if the filter is on the film side of the lens, but there is still an effect. 

Obviously, at 1:1 the effect is equal on both sides.

--
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121

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