Vuescan preview is darker than the actual scan

Discussion in 'Digital Darkroom' started by jimsimmons, Dec 16, 2007.

  1. When I get my black and white negative previewed in Vuescan and have selected
    the film setting that best gives me the tonal scale I'm looking for, I hit the
    scan button and wait for the image to come up in Photoshop. But when it does,
    the image in photoshop is much lighter than the preview image in Vuescan. The
    black point and white point are correct for what I set them at, but the image
    always needs a curve applied that pulls the mids down quite a bit. I've profiled
    the scanner (Epson V700) and am using that profile in Vuescan. I've got the
    monitor profile set correctly. Is there something else I'm not doing properly?
  2. I'm not familiar with the workings of Vuescan. Nikonscan and Silverfast have a relatively good correlation between previews and the final scan, witn one exception (in my experience).

    Are you using Digital ICE (or the Vuescan equivalent)? This will distort the tonality of B&W images (other than C-41 films). ICE will also distort the tonality of color negative films processed in Tetenal, which tends to leave un-oxidized silver in the emulsion.
  3. Preview is done at the nominal scanner exposure. Based on how the histogram looks Vuescan will change exposure for the final scan.

    I'd suggest clicking the box to "lock exposure," as if you don't do that color corrections you make in Vuescan may have unwanted side effects. Also, watch your output color space- output to something like Ektaspace or Prophoto that won't clip slide colors (I'm assuming you're using slides and you profiled the scanner for whatever type of slide film you use).
  4. Roger, I will try the lock exposure box to see if that does the trick.

    I scan all sorts of things - B&W negs, colour negs, and transparencies. In this particular instance, I'm talking about B&W negs. I choose TMAX 100 as my film, then usually a TMX-50 or TMX-70 type (? - adjusts the tonal curve) or any type that gets the tones looking about right in the preview, then scan. I use Adobe RGB as the output colour space, and that should be plenty wide enough from my B&W negs. I develop the film to be a tad flat. And I set my black and white points at .01% and .1%. Can't remember which I set at which though. The results are fine once I change the tones in Photoshop, but I'd certainly like to get them closer in the scan, so I can assure that the type setting I'm choosing is the right one.
  5. I'd suggest making sure that monitor color space or profile is correctly set in Vuescan. The exposure issue should be moot unless Vuescan does some miscalculation, otherwise the preview would be useless without locking exposure, which it isn't. Slightly off topic, I'm not sure what is the point of using a wide color space such as the AdobeRGB and at the same time instructing Vuescan to clip 0.01 and 0.1% values? Your settings will cause the tonal range to be stretched to span the whole range of AdobeRGB and clip a bit at both ends.
  6. Jim: Understand that Vuescan actually adjusts nothing other than exposure in the actual scan itself. Everything else is software adjustment of the file. That pause after the lamp goes out but before it writes the file is it doing all those adjustments using the CPU. Vuescan is a great scanner driver but it's ability to make software adjustments to a file is not in the same league as Photoshop. So don't even bother. Just scan to capture all the data, then use PS. You don't want Vuescan to make some automatic software adjustments that you may later have to reverse in PS. Just make the adjustments once in PS.

    People don't realize that all those software adjustments in Vuescan are not meant for us. They are meant for those people who do not subsequently use an image editor and want to have a usable final file outputted from the scanner.

    BTW, is there a reason you scanning b&w (i.e. monochrome) into RGB? I tried that but many years ago went back to scanning as Greyscale.
  7. Bob, sorry to be confusing, but for B&W I do scan in greyscale, not in RBG.

    I tried all sorts of settings, and what makes the difference is changing the output colour space. I changed one thing at a time, and most changes made almost no difference. But changing from Adobe RGB to ProPhoto RGB output colour space gives me a TIFF file in photoshop that is very close to the Vuescan preview image. According to the Vuescan guide, Adobe RGB (and other colour spaces) use 2.2 gamma, and ProPhoto, Colourmatch, etc. use 1.8 gamma. So essentially I'm doing almost the same thing as pulling down the middle of middle of my curve in photoshop, but at least now I'm getting in PS what I'm seeing in PS, and this is a welcome change. I've still got plenty of postproduction work to do in PS, but I'm in a better starting point now.

    One other change I made was to change the White Point from .1 to .05. I tried using 0.0 for both black and white points, but this produced a muddier scan than the final image I'd end up with anyway, that I went back to the very slight clipping settings. I may play with that some more, though.

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