SPOT 4.1 Basic and Advanced Software Manual for SPOT Insight ...

Ch. 5 – Preparing to Take a PicturePost-ProcessingThe final aspect of defining an image setup is to determine the post-processing adjustments (corrections)that you want the SPOT camera/software to make. Each option is described in the sections that follow.Some options are available only for the Insight Color camera or only for the Insight B/W (monochrome)camera - this is indicated parenthetically next to the heading.Black Level Subtract (12 BPP) (Insight B/W)The amplifier in the SPOT camera has been adjusted so that the average black (no light) pixel value isbetween 20 and 25, rather than zero for 12 bit (4,095 full scale) downloads. This offset is called the blacklevel (sometimes referred to as the “pedestal”). Before each picture, the camera samples the black level bytaking a picture with the shutter closed. The software then downloads the pixel values in the first row ofthe CCD chip, averages them, and stores this value as the black level. When capturing 8-bit monochrome,24-bit RGB and 36-bit RGB images, the software automatically subtracts the black level from all pixelvalues so that black pixels are 0 (black) rather than 20-25 (dark gray), and colors are representedaccurately.When capturing 12-bit monochrome images, you can turn off the automatic Black Level Subtract. This is auseful option in cases where you need high accuracy brightness measurements. For example, you maywant to adjust the black level of an image on a pixel-by-pixel basis by subtracting a second picture, takenwith no light (a “dark frame”), from the original image. When high accuracy measurements are needed, theautomatic Black Level Subtract is a problematic because the Black Level is an average of a sampling ofblack pixel values. Some values are higher, and some values are lower than the average. Subtracting thisaverage value from a black pixel value that is lower than average would normally result in a negative value.But, since there are no negative values, the result is arbitrarily set to zero and the actual value is lost. Thisdiminishes the accuracy of measurements.Correct Color Technology (Color; 3-Shot)The Correct Color option utilizes camera dependent color correction profiles that optimize the matching ofcolors between your microscope specimen, the live image you view on the screen of your monitor, and theimage you capture with your SPOT camera. This is done by transforming the raw camera color dataallowing it to be adjusted to display the closest approximation of the same color on your monitor.Correct Color Technology has been developed based on color profiling specifications develop by the ICC(International Color Consortium®).106 User Guide to the SPOT Insight Camera