Re: contrast control, the sun, and cyanotypy

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From: Sandy King (sanking@hubcap.clemson.edu)
Date: 06/15/01-07:01:23 AM Z


Jeffrey Mathias wrote:

>
>Rather than the direct sun or shade, the spectrum of light, the nature
>of clouds, I have found that the exposure time (not the exposure amount)
>can make a difference in contrast. The longer time gives a lower
>contrast. I do not know why this happens, but I have noticed it to
>happen every time, but I have not quantified how much contrast is
>altered for how much exposure time under what conditions and with what
>materials or if this effect is consistent. Only that one should expect
>less contrast with more exposure time.

My experience with carbon printing, where there is no self-masking,
is exactly the opposite. Longer exposure times lead to increased
contrast. With POP and Salted paper prints with lower contrast are
obtained by printing in the shade, while prints of greater contrast
can be had by printing in direct sunlight. The self-masking aspect of
the POP and Salted paper have the obvious effect of reducing overall
contrast as exposure times increase.

Sandy King


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