Interpreting the Camera Histogram for brightfield microscopy

See also Camera histogram

  • If the live image on your microscope-connected computer screen does not match what you see by looking through the microscope eyepieces, you may need to adjust the white balance.
  • If the live image matches the image in your eyepieces, examine the gray part of the camera histogram to assess the quality of the image.

Examples:

Ideal

This is an ideal histogram for most types of brightfield data. The histogram, and therefore the dynamic range, is distributed over nearly the entire range of the camera.

 

Low dynamic range

Try increasing the exposure time and or the illumination until the histogram fills at least 2/3 of the histogram window.

 

You can move the white point slider to the left to improve display of the live-camera image on screen, however, most of the potential dynamic range is lost and the signal-to-noise ratio is lower.

 

 

 

 

 

 

Background-image histogram

This shows an ideal histogram for a brightfield background image.

  • Try to obtain a histogram as narrow and as far to the right as possible.
  • If you need to modify the exposure, do so before starting the slide scan.
    • Control the exposure to avoid a saturated image.
    • Do not to modify the exposure after the acquisition; this would result in removing signal instead of solely background noise.

Background image with dust/artifacts

The small hump adjacent to the narrow peak indicates the presence of dust or other artifacts in the background image.

 

 

Oversaturation

If the image is completely saturated, the histogram appears cut off on the right. Enable Clip Detect if you suspect oversaturation; pixels that are at the maximum will show most of the image as red.

  • To correct this, decrease the light level and/or exposure time until the signal fills nearly the entire range of the camera.

 

 

Inadequate light

This histogram suggests that the light source is not sufficient for the camera.

To correct this, examine an image through the microscope eyepieces.

  • Try increasing the light level.
  • Open the shutters in the light path.
  • Switch the light path on the microscope to send light to the camera.
  • Increase the exposure time and check that the gain is set the default value for the camera.