While I cannot answer your question 2, I will attempt to adress question 1. But first a couple of preliminary questions and my assumed answers to them. How do you determine what the scanned image looks like? I assume you have saved it to file and are opening the file in an image editor like application. If correct in my assumption, what sort of file format are you saving the file to? If it is being saved as a lineal raw data TIFF file, it will display dark according to the help files for Vuescan (and in my experience very dark overall). You need to check the settings and make sure that the app,lication is not set to output the final scan to a linear raw TIFF file.
If this is not the problem, then I need a further clarification of what you mean by "if I adjust these points so that the histogram stretches almost all the way across the graph, I find that the scan image has black in it...." Don't all images have black in them? By setting the points so at to cover the compete continuum of the histogram, you are defining the tonal range and density range of the scanner as a physical device which may indeed be broader than that of the image being scanned. Thus, all the continuum from the black point beyond the first dark areas of significance in the image to the first dark areas of significance in the image will be black and without any real tonal or density variations. >The default blackpoint is zero, I believe (I'm not at >the machine that has Vuescan); but using it seems to leave a lot of "space" >on the left, at least according to the histogram. I refer you to the Vuscan User's manual which says under color tab: Color tab This tab is used to control the colors of the preview and scan. It lets you specify film type, film base color, image brightness, color balancing, black and white points and color space. Color balance Use this option to set the type of color balance you want for each image. The default setting of White Balance is appropriate for typical lighting conditions. See the topic "Adjusting Color Balance" for general guidance on using Neutral and Auto levels to handle these cases if White Balance is not right. None The black and white points aren't used at all, and the image is only corrected for the CCD's color response (if the Media type option is set to Image) or by the film's color response. This image is gamma corrected. Manual Both the black and white points are used to stretch the image's intensity range. However, the relative ratios of red, green, and blue are specificed manually. Neutral Both the black and white points are used to stretch the image's intensity range. However, the relative ratios of red, green, and blue are kept constant. Tungsten Both the black and white points are adjusted to compensate for an image lit by tungsten light (i.e. a normal incandescent light bulb). This removes the reddish cast from indoor pictures taken without a flash. Fluorescent Both the black and white points are adjusted to compensate for an image lit by fluorescent light. This removes the greenish cast from indoor pictures lit by fluorescent lights or lit by flash. Night Both the black and white points are adjusted to compensate for an image taken at night. The white balance is determined from the darkest 10% of the image, which often produces the best results when images have bright fluorescent or incandescent lights that are greenish or yellowish. Auto levels This is a simple mapping of the darkest color to 0.00 intensity and the brightest color to 0.95 intensity. White balance VueScan analyzes the image and adjusts it to make neutral colors appear more neutral. Landscape VueScan analyzes the image and adjusts it to make neutral colors appear more neutral, sky blue colors appear more lifelike and green foliage colors more lifelike. Portrait VueScan analyzes the image and adjusts it to make neutral colors appear more neutral and skin tones appear more lifelike. 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. The default black point is 0. Setting a higher value will cause tones close to black to become pure black, which can improve contrast. Setting the black point too high will cause shadow detail to be lost. Black point red/green/blue This option lets you set the black point manually. Note that these values are in linear space, not gamma corrected space, so the only practical way to use these values is to use the "Input|Lock image color" option. White point (%) The white 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 white point at the maximum intensity (0%), or to choose the white point such that some percentage of the pixels in the image are above the white point. The default white point is 1% (that is, the brightest 1% of pixels are all converted to pure white). Setting a higher value will cause tones close to white to become pure white. This can improve contrast and overall intensity of the image. Setting the white point too high will cause details in areas of highlights (e.g. the gray puffs of a cloud) to be lost, making the image look flat. White point red/green/blue This option lets you set the white point manually. Note that these values are in linear space, not gamma corrected space, so the only practical way to use these values is to use the "Input|Lock image color" option. Brightness Use this option to increase or decrease the overall image brightness. VueScan's brightness is effectively a multiplier of the gamma of the color space. Brightness red/green/blue Use these options to increase or decrease the red/green/blue image brightness. Note that this is a gamma multiplier, where 1.0 is the default setting. Your problem may be that one of these setting may be inappropriately set so as to result in unintended consequences with respect to your manual preview histogram establishment of setpoints and their impact on the scan histogram or output display which is presented. Vuescan contains a number of controls which relate to and influence the operation of other controls; the setting of some may very well influence what happens when you set your setpoints. If this does not help; I hope it at least stimulates some new and additional thooghts and ideas on the subject. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of James Gaa Sent: Friday, September 19, 2003 12:22 AM To: [EMAIL PROTECTED] Subject: [filmscanners] 2 vuescan questions I have two questions about using vuescan. 1. Some people in the recent discussion on 8 vs. 16 bits have mentioned the histograms in vuescan. In my experience, the preview histogram is not very useful for what I would have thought was a primary use: setting the whitepoint and blackpoint. For example, if I adjust these points so that the histogram stretches almost all the way across the graph, I find that the scan image has black in it, as indicated by turning on the switches to show black and white areas. In short, the preview histogram looks right, but the scan doesn't; and I haven't found empirically a way of reliably fudging the blackpoint adjustment. The default blackpoint is zero, I believe (I'm not at the machine that has Vuescan); but using it seems to leave a lot of "space" on the left, at least according to the histogram. This occurs on slides that are properly exposed, both visually and according to the histogram (i.e., no unintended areas of black or blown-out highlights. Am I doing something wrong? Should I just go with the defaults? 2. I occasionally scan slides (using a Nikon IV-D) that have a good deal of orange and colors close to it, expecially orangey rust. I haven't found a way of setting the options in Vuescan to produce a scan that matches the slide closely. The problem seems to exist only when there are large areas of such color. Any suggestions? Jim Gaa ---------------------------------------------------------------------------- ------------ Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body
