From: C Downs (fardog@mindspring.com)
Date: 09/25/01-01:58:47 AM Z
Subject: Re: Un SP mask . no diffuser necessary
On Mon, 24 Sep 2001, C Downs wrote:
> .... I use a sheet of
> white acrylic over the neg and masking film with the film emulsions in
> opposite directions. This white acrylic being in contact with the original
> neg's emulsion will prevent N. Rings and in my experience gives all the
> diffusion necessary. Wess plastics makes a masking frame for 4x5 or
smaller
> negs that uses the same thing and I find it great for the smaller formats.
Can you be more specific about "white acrylic"? Does it have another
name? How thick is it???
thanks,
Judy
The type I use is "Plexiglas" or however they spell the trademarked acrylic
sheet that is common in the US. The more diffusion you want the thicker you
use. The 35mm to 4x5 is a 1/16th inch thick piece and the larger negs work
best with 1/8th in or thicker sheets. You can use thicker sheets but you
don't seem to gain diffusion and loose light transmission. If you hold the
white sheeting to the light and look through it you will see that some is
"swirled" with uneven distribution of colorants while other varieties are
very even in tone. I don't know a way to know about the types except to look
through them. In my home area I get scrap pieces up to 20 inches for a
couple of dollars from plastic companies that specialize in Acrylic Sheeting
{ in the yellow pages of the phone book}
One trick that helps to keep the sheets working if scratched or if not
diffuse enough is to use 600 grit or finer sandpaper { auto painting type
usually} and give both sides as even of a going over as possible.
The same sheets are usually used for light tables and I use a piece of
plate glass 36x96 inches {for strength and rigidity } with the thin 1/8 inch
white sheeting over it. It is actually even enough in light transmission
that I can use a handheld meter to read spots on different negs to see
which will print similarly. Lot faster than warming up the densitometer...
:o)
Stores that sell lighting fixtures also should carry this type of
sheeting.
This archive was generated by hypermail 2b30 : 10/01/01-01:41:32 PM Z CST