RE: filmscanners: VueScan clipping & flat images

[S Schwartz <snsok@swbell.net>]

The clipping is worse, as I would expect, if I use anything above zero for
the white point and black point % setting.

For what it's worth, if I change Media Type from Image to Slide and then go
to Color tab and change Generic to Koday and type to E6, the clipping seems
to be significantly reduced. However, the scan is flatter and the colors
have more of a yellow cast.

By the way, I am using Koday Elite Extra Color EBX for these tests.

Stan

-----Original Message-----
From: owner-filmscanners@halftone.co.uk
[mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Bob Armstrong
Sent: Thursday, November 22, 2001 9:13 AM
To: filmscanners@halftone.co.uk
Subject: Re: filmscanners: VueScan clipping & flat images


The following is taken from VueScan's help file.  It seems to me that B&W
points of 0% should leave all of the pixels in the scan.  (Having said that,
when looking at a histogram, it does seem that some pixels either go beyond
the black point or there are a mumber of pixels _at_ the black point.)

It seems to me that setting B/W to 0% results in what Jawed is calling a
flat image.  Jawed (if you're reading this!) does a histogram of one of your
flat VueScan images extend all, or most of the way, from 0 to 255?  I find
with my flat VueScan mages that do not range across the histogram but leave,
particularly at the white point end, a lot of unused values.  If that is the
case with your images I wonder if you would try to increase the white point
to 0.05 or 0.1 and see what that does to the image.  I would be interested
in your results compared to Nikonscan especially if you set the white point
to _just_ fill the histogram.

Black point (%)
The black point is used by the color balance algorithm and is computed by
using the histogram of each color in the image. Use this option to leave the
black point at the minimum intensity (0%), or to choose the black point such
that some percentage of the pixels in the image are below the black point.

White point (%)
The white point is used by the color balance algorithm and is computed by
using the histogram of each color in the image. Use this option to leave the
white point at the maximum intensity (0%), or to choose the white point such
that some percentage of the pixels in the image are above the white point.

Bob Armstrong

Alessandro Pardi wrote:

>Stan, Leif,

>I think you shouldn't use 0% for the white and black point, as this sets
the
>deepest shadows to 0 and the brightest lights to 255, and may result in
>clipping. My usual settings are 0.1% for the black point and 0.5% for the
>white point, but I seem to remember a post by Hamrick about this, so you
may
>want to dig in the archives.


> From: Goodwin, Leif [mailto:Leif.Goodwin@racalinst.co.uk]
> Sent: giovedì 22 novembre 2001 08.15
> To: 'filmscanners@halftone.co.uk'
> Subject: RE: filmscanners: VueScan and highlight/shadow pixel
> clipping--wh y? (SS4000)
>
>
> Stan. I see the same with Vuescan and the Microtek 4000T
> scanner. Don't know
> why. Leif.
>
> > -----Original Message-----
> > From: S Schwartz [SMTP:snsok@swbell.net]
> > Sent: Thursday, November 22, 2001 3:27 AM
> > To: Filmscanners (E-mail)
> > Subject: filmscanners: VueScan and highlight/shadow pixel
> > clipping--why? (SS4000)
> >
> > I posted this question a few days ago but got no response
> so I am posting
> > it
> > again.
> >
> > I like using VueScan with my SS4000 scanner but I am
> consistently seeing
> > highlight and shadow pixel clipping on my transparency
> scans. When I use
> > Polaroid's Insight software for scanning, I get a nice
> histogram with no
> > pixel clipping.
> >
> > I have tried Vuescan with 0% white point and 0% black point
> and still get
> > the same clipping. I am using ordinary settings on the color tab:
> > brightness
> > 1.1, gamma 2.2, etc.
> >
> > Any reason this is happening?
> >
> > Stan
>
>
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