[filmscanners] Re: 2 vuescan questions (White Point)

["" <erik.kaffehr@swipnet.se>]

Hi!

White point is percentage of bright points clipped. It's useful to decide 
wether you want to have details in bright parts of the image. Setting WP to 
zero gives dull highlights.

I think that setting WP to around 1% does increase exposure, giving more 
details in the dark parts of the picture. This stuff is probably most 
interesting with slides, which may have a density range exeeeding the range 
of the scanner. 

Generic advice:

Normally 0.5% - 1% is OK
For dramatic clouds set to zero, and use curves in PhotoShop
For washed out highlights set to 10%

Erik

fredag 19 september 2003 17:56 skrev du:
> 1) I do leave Black & White points at 0. Its really time consuming to set
> those values for each slide, so I will leave at defaults. I too would like
> to know other experienced user's opinion on it.
>
> 2) Try using "Image" in "Input" tab
>
> Thanks
> Ramesh
>
>
>
>
>
> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of James Gaa
> Sent: Friday, September 19, 2003 1:22 AM
> To: Nagaraj, Ramesh
> Subject: [filmscanners] 2 vuescan questions
>
>
> I have two questions about using vuescan.
>
> 1. Some people in the recent discussion on 8 vs. 16 bits have mentioned the
> histograms in vuescan. In my experience, the preview histogram is not very
> useful for what I would have thought was a primary use: setting the
> whitepoint and blackpoint. For example, if I adjust these points so that
> the histogram stretches almost all the way across the graph, I find that
> the scan image has black in it, as indicated by turning on the switches to
> show black and white areas. In short, the preview histogram looks right,
> but the scan doesn't; and I haven't found empirically a way of reliably
> fudging the blackpoint adjustment. The default blackpoint is zero, I
> believe (I'm not at the machine that has Vuescan); but using it seems to
> leave a lot of "space" on the left, at least according to the histogram.
> This occurs on slides that are properly exposed, both visually and
> according to the histogram (i.e., no unintended areas of black or blown-out
> highlights. Am I doing something wrong? Should I just go with the defaults?
>
> 2. I occasionally scan slides (using a Nikon IV-D) that have a good deal of
> orange and colors close to it, expecially orangey rust. I haven't found a
> way of setting the options in Vuescan to produce a scan that matches the
> slide closely. The problem seems to exist only when there are large areas
> of such color. Any suggestions?
>
> Jim Gaa
>
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-- 
Erik Kaffehr                erik.kaffehr@swipnet.se alt. ekr@ksu.se
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S-611 66 Nyköping           +46 155 263515 (office)
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