When should I use the Black Level feature on my TIS camera?

The Black Level setting controls the analog black level of the sensor and directly influences the generation of the raw pixel data. It shifts the sensor's output values up or down before the image data is processed further.

What Black Level setting should I use?

As a general rule, the Black Level should be set as low as possible for your application.

For color cameras, a Black Level of 0 is required for accurate color reproduction when using a Color Correction Matrix (CCM) and Gamma correction.

Why might I want to increase the Black Level?

Setting the Black Level very low has an important trade-off when analyzing images captured under very low-light conditions.

Even when no light is reaching the sensor, the sensor output is not a single constant value. Instead, the pixel values typically form a distribution around the sensor's black level due to sensor noise and other variations.

If the Black Level is set to 0, part of this distribution may extend below zero. These negative values cannot be represented in the raw pixel data and are therefore clipped at the lower limit.

As a result, part of the information contained in the dark-signal distribution is lost.

If your application requires accurate analysis of the distribution of pixel values in very dark images, slightly increasing the Black Level can preserve more of this information and prevent the lower part of the distribution from being clipped.

How can I see the effect?

The effect can be clearly observed in the image histogram.

With a very low Black Level, the dark pixel distribution may be clipped at the lower limit. Increasing the Black Level shifts the distribution away from this limit, allowing the full distribution to be captured and analyzed.

Therefore:

• For general image acquisition and color processing: Keep the Black Level as low as possible. For color cameras using Color Correction Matrix and Gamma correction, set it to 0.

• For analyzing very dark images or pixel-value distributions: Consider increasing the Black Level slightly to avoid clipping the lower part of the sensor's output distribution.

Note: Increasing the Black Level does not increase the sensor's sensitivity or create additional image information. It changes the position of the sensor's analog output distribution relative to the available digital range.