Basler A102f User Manual

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Basler A102f User Manual Manual pdf 48 page image

Basic Operation & Standard Features3-26 BASLER A102fDRAFTOnce the conversion to YUV is complete, pixels are transmitted from the camera in the YUV(4:2:2) format as defined in Sections 5.3 and 5.4.3.8.1 White BalanceWhite balance capability has been implemented on the A102fc. With white balancing, correctionfactors are applied to the interpolated RGB values for each pixel. The correction factors can beused to adjust the color balance of the images transmitted from the camera.The white balancing scheme outlined in the IIDC specification dictates that blue and red areadjustable and that green is not. On A102fc cameras, green has a fixed value of 96 (0x60) whichcorresponds to a correction factor of 1.5. You can effectively raise the relative amount of green bylowering the correction factor for blue and red below 1.5. You can effectively lower the relativeamount of green by raising the correction factor for blue and red above 1.5.The Blue Value field of the White Balance control register (see page 4-21) can be used to changethe blue correction factor. The usable range of settings for this field is from 64 (0x40) to 255(0xFF). If the field is set to 96 (0x60), blue will have the same 1.5 correction factor as green. If thefield is set to a lower value, blue will have a lower correction factor and the image will be less blue.If the field is set to a higher value, blue will have a higher correction factor and the image will bemore blue. The default setting for the Blue Value is 151 (0x97).To determine the correction factor for blue, use this formula:The Red Value field of the White Balance control register can be used to change the red correctionfactor. The usable range of settings for the this field is from 64 (0x40) to 255 (0xFF). If the field isset to 96 (0x60), red will have the same 1.5 correction factor as green. If the field is set to a lowervalue, red will have a lower correction factor and the image will be less red. If the field is set to ahigher value, red will have a higher correction factor and the image will be more red. The defaultsetting for the Red Value is 122 (0x7A).To determine the correction factor for red, use this formula:L The values for U and for V normally range from -128 to +127. Because the 1394 Dig-ital Camera specification requires that U values and V values be transmitted with un-signed integers, 128 is added to each U value and to each V value before the valuesare transmitted from the camera. This process allows the values to be transmitted ona scale that ranges from 0 to 255 (see Section 5.4.2).When an A102fc is operating in a YUV (4:2:2) mode, the average number of bits perpixel is 16. This means that the camera will require twice the bandwidth of a cameraoperating in an 8 bit monochrome mode.The A102fc can operate in YUV (4:2:2) color mode as well as several monochrome 8bit modes (see Section 3.13).Blue Correction Factor Blue Value Setting64-------------------------------------------------=Red Correction Factor Red Value Setting64------------------------------------------------=