Roper Scientific Photometrics color CoolSNAP camera - White Balance for brightfield microscopy.

Technical Note: 246
Reads: 7359
Creation Date: 14/09/2001
Modification Date: 12/02/2004

White Balance is the tool provided by color camera interfaces which allows the camera to be set to produce the correct colors in an image. The process works on the principle that if a white object can be made to look white all other colors will be correct. If the illumination of the sample is not of the correct color temperature the white balancing process may reproduce white at the expense of other hues. Therefore color reproduction will be impossible. See Technical Note 7 for information on setting up the microscope to achieve the illumination conditions necessary.

White Balance is available both in the Video Manager dialog and the Video Controls palette. Firstly set up the microscope for the correct illumination according to Technical Note 7.

White Balance will operate on a region of interest (ROI) drawn on the image, which allows the user to select an object or part of an object which is white or is to appear white in the final image, before clicking the White Balance button. In the absence of an ROI, the whole of the current active document is used so the sample must be moved to present the camera with a white scene such as an area of slide free of cells, before clicking the White Balance button.

Under non-ideal illumination conditions (a color temperature below 3200K) the White Balance procedure may have to disproportionately increase the amount of blue contribution in the image. The blue slider in the Video Controls palette may move to the far right of its range and display a value far higher than can normally be set with this slider. This is a reflection of the enormous amount of correction necessary to still produce white at inappropriate illumination levels.