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, cleaning the image data, sharpening
the image data, changing the dpi of the final image, and
watermarking the image.
- Scan 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.
If this option is set to "Auto", the scan will use a resolution that
results in roughly one million pixels.
- Preview resolution
- Use this option to select the preview resolution.
The default value of 1/8 of the optical resolution is reasonable for
most scanners, but you might want to change this when using some
lower-resolution scanners.
If this option is set to "Auto", the preview will use a resolution that
results in roughly one million pixels.
- 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.
- Long exposure pass
- On scanners that are able to increase
the CCD exposure time, this option lets you do an extra scan
pass that's longer than the normal RGB exposure.
VueScan then merges the data from these two passes to get
additional detail from the dark parts of the longer pass.
Pixels that are near saturated pixels on the long pass aren't
merged with the scan. This reduces the problems of CCD
blooming - saturated pixels spilling into nearby pixels.
- Restore colors
- This option is used to restore the red,
green, and blue colors by transforming the colors to make
them more independant. This works best when scanning
at high resolution.
- Clean
- Use this option to remove dust spots and reduce
visible film grain.
If the scan has an infrared channel, the Clean option will
remove dust spots, the Scrub option will remove dust spots
and reduce film grain, and the Scour option will remove
dust spots and reduce more film grain.
If the scan doesn't have an infrared channel, the Clean
option will reduce film grain, the Scrub option will remove
more film grain and some smaller dust spots, and the Scour
option will remove more film grain and larger dust spots.
- Sharpen
- This option enables a 3x3 sharpening filter. It's
applied last, after all the color correction is done.
- 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.
- Release memory
- If this option is set, VueScan will release the
memory buffer for the scan at the end of each scan. This is
useful if you're post-processing images with an image editor and
you need to free some memory.