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



A specular reflection/bright light can easily represent 40% of the range of
values in an image.  When you look at the histogram, you will see a thin
line between the edge of the "mountain" and 255.  This happens, for example,
when you have lots of very bright reflections, e.g. off water.  Or a scene
with lots of lightbulbs, but which is, overall, quite dark.

As you bring down the white point, all of these bright points will seem to
"grow" in size.  It's a trade off you make, so that the rest of the picture
doesn't look too dark or too washed out.

An f-shaped curve (in Curves) that is tight at the top may be preferable to
bringing down the white point in Levels.  You have to choose.

Jawed

> -----Original Message-----
> From: owner-filmscanners@halftone.co.uk
> [mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Rob Geraghty
> Sent: 26 July 2001 07:43
> To: filmscanners@halftone.co.uk
> 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
>
>
> Rob Geraghty harper@wordweb.com
> http://wordweb.com
>
>
>
>




 




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