User`s guide

VueScan User's Guide
33
Imagine taking a picture of a typical outdoor scene with a bright blue sky with fluffy clouds along
with a person standing in the shade under a tree. Further, imagine taking this picture with both
slide film and negative film.
When taking this picture with slide film, the photographer has to set the exposure to either
capture the details of the sky and clouds, or set the exposure to capture the details of the
person standing in the shade under the tree. Once the picture is taken of one of the two
intensity ranges, there's no way to get back the other intensity range after developing the film.
However, when taking this picture with an automatic camera using negative film, the camera will
usually set the exposure so that both the details in the clouds and in the shadows are captured.
The decision of whether to capture the intensity range of the clouds or the person in the
shadows is made by the photographer when using slide film, but it's usually made by a
computer in the film minilab when printing the negative. Most minilabs will print this type of
scene with details in the shadows and the sky clipped to white without any cloud or sky detail.
One way to solve this problem is to manipulate the brightness of the image using the Color |
Brightness (p. 75) or Color | White point (%) (p. 74)option to manipulate the negative image so
that both the bright and dark parts of the image show detail when scanned.
Scanning Black/White Negative Film
If you're scanning black/white negative film, first check to see if the film looks gray or orange to
the naked eye. If it looks gray, set Input | Media (p. 50) to "B/W negative" and if it looks orange,
set it to "Color negative". Then go to the Color tab (p. 71)and choose a Black/White film type. If
you can't find a film type that exactly matches the film you're using, experiment with the Kodak
T-Max settings.
On most scanners, setting Input | Media (p. 50) to "Color negative" will increase the green
exposure time by 2.5x and the blue exposure time by 3.5x. This results in adjusting for the
green and blue absorption by the orange mask of the film. If the film doesn't have an orange
mask, then using "Color negative" will result in a raw scan file that looks very cyan.
Maximizing Image Quality
After you've decided on the resolution of your finished image (or alternatively the pixel
dimensions of your finished image), how do you maximize the image quality? There's one thing
you can do which involves longer scanning times, but capturing more raw data for each pixel in
the finished image.
The basic idea is scanning each pixel more than once and averaging the pixels. Each doubling
of the number of pixels increases the effective number of useful bits of data by one. For
instance, if you have a 10-bit scanner like the Nikon LS-30 and you read the CCD 4 times at
each pixel position, you get effectively 12 bits of useful image data.
There are several ways of achieving multiple image samples. The first is single-pass
multi-scanning. Some scanners are capable of reading each pixel position multiple times before
advancing the scan head to a new position. The second technique is multi-pass multi-scanning,
which most scanners are capable of (however, some can't accurately reposition each scan
pass, so this may not always work well).