That vuescan text (below) states that the black point determination uses the histogram of each color -- three histograms. Might the combination of color balance / neutral and black point computation result in one or two color channels with pixels below the calculated (luminance) black point? In what software/tool is the histogram being viewed?
In Photoshop a calculated luminosity histogram is displayed by Image->Histogram while the logical-or overlay of the three channels is displayed by the RGB channel in the levels dialog box. For Image->Histogram be sure that the histogram box shows cache level 1, which can be obtained by Shift+Image-> Histogram selection if preferences setting calls for using cache for histograms. Bob Shomler www.shomler.com ---------------- >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.) >... >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.
