Relationship between Blemish detect threshold and black level

As unit of blemish detection threshold is percentage, when we transform it from percentage to grey value(LSB), we must consider black level.

JAI’s camera outputs 8LSB(average for the whole image) at 8Bit pixel format due to default black level setting.

*That is also the reason why pixel values are not 0 LSB, even we put lens cap onto the camera.

When blemish detection threshold is 10%, the transforming formula is:

(255-8) * 0.1 + 8 =32.7 LSB

When blemish detection threshold is 20%, the formula is:

(255-8) * 0.2 + 8 =57.4 LSB

If you set Black level to -133, the Black level(average pixel value) will be 0 LSB.

If you set Black level to 255, the Black level will be 24 LSB.