Options tab

This tab lets you specify options that affect a scan. It includes setting the scan resolution, controlling the focus and exposure, setting the number of scan passes, reducing the scan size, filtering the image data, changing the dpi of the final image, and watermarking the image.

Resolution

Use this option to select the scan resolution. The reason that the resolution only has four choices is that most scanners use a CCD that spaces the color sensor rows 8 pixels apart, so only these scan resolutions cause the pixels to line up (otherwise you can get color fringing).

The actual dpi of the scan is stored in the file header of the output files.

Auto focus

Set this option to enable a focus before doing a preview or scan (or both).

Focus

Set this option to a value between -1 and 1 to manually change the device focus. The nominal value for most scanners is 0.

Auto exposure

Set this option to automatically compute the optimal exposure before doing scan.

If you turn off the "Crop|Auto crop" and "Options|Auto exposure" options, then the "Scan|Device" command won't first do a preview scan. This can save time when batch scanning.

RGB/Infrared exposure

On scanners that are able to vary the exposure time, this option lets you multiply the exposure time by a user-specified value. This is sometimes useful when scanning very dark slides with bright highlights when you want to get more detail from the dark parts of the slides.

There's seldom any reason to increase the exposure time more than the amount computed by the auto exposure option. If the CCD is over-exposed when scanning color negative film, then the orange mask color value gets messed up and the dark parts of the image (the bright parts of the negative) will lose detail.

Number of passes

On most types of scanners, this option causes the film to be scanned multiple times, and the average of these scans to be stored. This can significantly reduce the noise in scans. There are few visible benefits to scanning more than 16 passes, but you can set the number of passes to any number up to 256.

On the Nikon LS-2000 and the Minolta Dimage film scanners, this option causes each scan line to be read N times before advancing to the next scan line. On other scanners, the whole image is read N times.

Note that the PhotoSmart scanner doesn't align multiple scans very well because of the way it uses rubber rollers to move the film or slides. For this reason, this option isn't useful on the PhotoSmart.

Other scanners (such as the Polaroid SprintScan 4000) sometimes have registration problems of a few pixels between each scan pass. A future version of VueScan will automatically register these multiple scan passes.

Filter

Use this option to set the types of filtering you want to do to each image. The sharpen filter applies a 3x3 sharpening filter, and the clean, scrub, and scour filters apply progressively larger nonlinear filters to remove dust spots. If you're processing an image from the Nikon LS-30, LS-2000, or Minolta Scan Elite that contains a separate infrared channel, this data is used as part of the image cleaning.

Size reduction

You can usually improve image quality by scanning at high resolution and then using this option to reduce the size of the crop tif file. For instance, reducing by a factor of 3 will reduce the height and width of the output files to 1/3 of the value from the raw scan, and the file will be 1/9 as large. Each pixel in the output file will be the average of every 3x3 group of raw pixels, which will significantly reduce the image noise.

Get dpi from/Dpi or width

These options let you specify how to compute the dots per inch (dpi) of the cropped images. The dpi can be the same as the scanned image, can be explicitly set, or can be computed so that the width of the cropped image can be a specified number of inches, cm, or mm.

Watermark

You can optionally add a watermark (grid of lines) to output files by selecting this option. The unregistered version of VueScan always applies the watermark, but this can be turned on and off in the registered version.