Is VueScan's AutoLevel Same As PhotoShops?

[mkochsch]

Am I just eliminating one step if I do my auto level in Vuescan instead on
of Photo Elements? What's the difference? If I'm going to correct in PS/E
should I set it to White Balance or None?

Thx.

 

[Mendel Leisk]

Am I just eliminating one step if I do my auto level in Vuescan instead on
of Photo Elements? What's the difference? If I'm going to correct in PS/E
should I set it to White Balance or None?

Thx.

I've never totally understood Color|Color Balance|Auto levels. It is a
"color balance" and is separate from the settings of Color|White point
and Color|Black point. Switch between A.L. and white balance (or
neutral or manual), make no apparent difference to the amount of
clipping showing in the histogram.

Ed Hamrick describes it as:

"a simple mapping of the darkest color to 0.00 intensity and the
brightest color to 0.95 intensity"

All I can see is it currently seems for me to have better color
balance, than anything else, for color slides or negs., though I'm not
really doing anything serious in color right now.

Maybe Ed can comment.

 

[Bart van der Wolf]

Am I just eliminating one step if I do my auto level in Vuescan instead on
of Photo Elements? What's the difference? If I'm going to correct in PS/E
should I set it to White Balance or None?

They are similar in that they both 'stretch' all channels to fill the
histogram from dark to light. This can cause significant color casts in
images with (a lack of) a dominant color. The contrast of the lacking colors
will be enhanced much more than the others, darkening light toned ones and
brightening dark ones.
They are different in that Photoshop allows to set different clipping
percentages on the black/white points, and VueScan is fixed.

Bart

 

[Ed Hamrick]

I've never totally understood Color|Color Balance|Auto levels.

If the brightest color in an image is white, then "Auto levels"
will produce exactly the same result as "White balance". If
the brightest color is fluorescent red (or the sun at sunset),
then "Auto levels" will result in odd-looking colors.

Regards,
Ed Hamrick