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The image files can be recorded as the 8-bit or 16 bit TIFF files (8 or 16 bits per pixel) and
the pixel shift can be helpful in adjusting gain for the 8-bit files.
The 16-bit TIFF files can not be properly handled by many image viewer programs (notably
the one that is shipped by Microsoft with Windows). You could download the free image
viewer program, IrfanView from
www.IrfanView.com
; it can read and display the images
and their hidden TIFF flags. (Though it can not truly display the 16 bit pixels directly but
converts them to the 8-bit representation for display). Programs like Adobe Photoshop can
handle true16 bit images.
Selecting lossless image compression can halve the size of the image files and disk usage
but could complicate or prevent operation of many image processing programs.
The most important options during the image download refer to the image quality
enhancement by the removal of the fixed-pattern noise (FPN). The silicon area image
sensors by design are sensitive to micro-variations in the semiconductor manufacturing
process. These variations cause small differences in sensitivity of each pixel sensor.
Collecting images of these imperfections (FPN) and subtracting the FPN from captured
images will eliminate such variations. The FPN elimination helps especially with low-light
and low-contrast images that often occur with an insufficient lighting or too high capture
frame rate.
The FPN elimination is a two-stage process:
FPN Preparation
1. Set desired capture parameters.
2. Put lens cap on the lens to prevent light from getting in the camera.
3. Erase camera memory and trigger acquisition of the so-called “darkfield” images.
4. After capture stops, start image download in the directory where images will be
stored later and click on the
FPN compute
checkbox.
5. The camera will download 126 frames and will create an image file FPN_.....tif that
contains the FPN estimate.
FPN Image Use
1. Capture images as usual
2. Specify the same directory for the image download click on the
FPN Subtract
button.
3. If the application doesn’t remember you doing the
FPN preparation,
it will ask you
to select an appropriate FPN file, like in the
Figure 16
below.
