Re: filmscanners: cleaning neg's, sharpening

[Mark Thomas <markthom@camtech.net.au>]

Just a couple of quick comments..

1. Cleaning neg's with water
Bear in mind that if you use anything but 'unexposed' distilled water as a 
cleaning agent, you are in fact using carbonic acid..!
I used to work in a oceanographic lab, and while checking the pH levels of 
a distilled water producer, I was surprised to discover how acidic the 
'pure' water was.  The resident chemist gently explained that H20, when 
exposed to air, absorbs CO2 and degrades quite quickly to a carbonic acid 
solution, of about pH 5.0-5.5 I think. (I'm flying by memory here - any 
chemists on the list feel free to correct..)

Keep that in mind if considering water for cleaning fragile items!!

2. Sharpening
>Sharpening should be done before retouching the image, because sharpening 
>causes many details to show up which have to be retouched.

I guess we are all different, but at the low levels of sharpening I use, 
I've not encountered sharpening effects that needed retouching.  I would 
have thought that other types of re-touching, eg cloning/rubber-stamping 
areas, is more likely to produce 'edges' that sharpening  may pick up and 
worsen.  So I *always* sharpen last, if at all.