Re: STARTING POINT
From: Don Bryant <dsbryant@bellsouth.net> Subject: RE: STARTING POINT Date: Mon, 21 Apr 2008 22:35:49 -0400 > Some individuals that contact print large format negatives > report that contact prints made on graded paper are sharper > than contact prints made on RC paper. Again I've never seen > the difference. That's unlikely. The resolution of paper emulsion is pretty low, much lower than camera film emulsions, and any difference between graded and variable contrast papers is insignificant, or wavelength-dependent at best. In paper emulsions, silver halide crystals of 100 to 400 nanometers are most frequently used. These crystals have pretty strong scattering of blue light and they give poor resolution. On the other hand, film emulsions are usually coarser than 400nm and they are also coated in at least two layers, where coarser grain emulsion (less scattering) is coated atop a finer grain layer. More heavily applied spectral sensitization further improves absorption and hence scattering of light. Use of tabular grain is a further improvement in reduction of light scattering. Of course, the above consideration is irrelevant if you test the resolution with x-ray exposure, which does not have this sort of scattering problem. I've not studied thse types of emulsions, but very fine grain ones used for holography and IC pattern masks (about 20nm) are much finer grained than the wavelengths of the light, and they may not have the resolution problems. -- Ryuji Suzuki "The truth that I am seeking is in your missing file." (Bob Dylan, Something's Burning Baby, 1985)
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