Opacity of digital negative substrates, was Re: Gum a la Sam Wang

Chris,

As you know there are many substrates being used for digital
negatives but Pictorico is perhaps the most common. If you read a
plain piece of Pictorico with a densitometer in UV mode you will find
that it measures about log 0.15 or slightly higher. The UV reading of
most film substrates, by comparison, will read about log 0.05. In
other words Pictorico is less transparent to UV than film, not more.
Other substrates I have seen appear to be thinner and would probably
have less opacity.

Sandy

>This is interesting; I think I'll take a neg into school and measure it on
>the densitometer, but for sure the transparency substrate is pretty darn
>flimsy compared to film.
>
>Question: in the Epson 2200 box there is a little thing (scientific, no?)
>where you can raise the gamma; does anyone do that when making negs? Does
>it do anything?
>Chris
>
><Judy said, large cut>I've always found that digital negs on paper or other
>NON-FILM material
>take about half or 2/3 the exposure of negs on film, all other things (eg
>emulsion & mix) being equal. I concluded that the difference is due, not
>to difference in contrast and density of the film negs v. digital negs,
>since the densitometer finds them comparable-- I develop lith film for gum
>to a contrast range of about 0.9, & print out digital negs at about the
>same range.
>
>My assumption has been that the substrate for the digital negs is more
>transparent to UV than film is, that is, it transmits UV more completely.
>And somewhere in distant memory I hear a "voice" on this list saying the
>very same thing.
Received on Sun Nov 23 09:25:11 2003