Re: filmscanners: Re: autolevels was re: filmscanners: Vuescan blue anomaly

["Robert E. Wright" <rew@impulse.net>]

----- Original Message -----
From: Rob Geraghty <harper@wordweb.com>
To: <filmscanners@halftone.co.uk>
Sent: Wednesday, July 25, 2001 11:43 PM
Subject: filmscanners: Re: autolevels was re: filmscanners: Vuescan blue
anomaly


> Maris wrote:
> > Sometimes you can't use anything - rather than using the
> > eyedropper you just have to guestimate - trial and error -
> > until the number for a near-white spot are near-white but
> > not-quite-white numbers.
>
> OK, let me rephrase the question slightly - isn't the intention of the
black
> and white point to define where the minimum and maximum brightness points
> are?  If so, why is a point of sun reflection in a photograph not a good
> point to use for the white point?  Because it's not representative of the
> majority of the image?
>
> Rob
>
Generally when using the eyedroppers in Levels or Curves they are set to
output target values. The black point is generally short of absolute black
and the actual number represents an ink limit based on the media planned for
output. The white dropper is generally set to a point less than completely
white (nothing printed).

When you then use the white dropper, you are defining the level of that
point to the preset values, and all whiter points will be completely blown
out. Therefore if the white dropper is set to RGB 244 (for example)  you
don't want to select a bright reflection that should be RGB 255.

Bob Wright