Vuscan Image Curves?

Vuscan Image Curves?

Post by Mariu » Mon, 28 Apr 2003 23:21:13



Hi,
   I've just updated my copy of vuescan from 7.5.50 to 7.6.33. Can someone
please tell me were the Image Curves selection has now gone or if it no
longer exists how do I go about approximating the same thing with the other
controls.

Thanks

Marius

 
 
 

Vuscan Image Curves?

Post by Leonard Even » Tue, 29 Apr 2003 00:11:58



> Hi,
>    I've just updated my copy of vuescan from 7.5.50 to 7.6.33. Can someone
> please tell me were the Image Curves selection has now gone or if it no
> longer exists how do I go about approximating the same thing with the other
> controls.

> Thanks

> Marius

You should be able to do exactly the same thing with an appropriate
setting of brightness, which is a gamma multiplier.  All the Image
Curves did was to select some default gamma multiplier.

--

Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208

 
 
 

1. Vuescan: Question about Color|Image/Slide/Negative/B/W curve

Hi,

user manual states the formulas for the 4 possible curve settings:

        Gamma        P =       I  ^ 1.0/G
        Log (dark)   P = log10(I) ^ 3.3/G
        Log (medium) P = log10(I) ^ 2.2/G
        Log (light)  P = log10(I) ^ 1.5/G

Question:  Does "^" mean exponent as I suspect?

Has exponent higher precedence than the multiplication or division,
thus for example Gamma formula is:
               1.0
              I
        P = ------
              G
rather than:
              (1.0 / G)
        P = I

If not, some parenthesis would be nice to make the formulas more
obvious.

If the Log curves use the same formula, would it be possible
to provide a slider so that the exponent factor 3.3 .. 1.5
could be set to every possible value in a specific range?

The Log settings combined with Color Balance|Auto Levels and
high black point provide excellent scans from night or low
light temperature images.

Thomas

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