What to Look For?

The performance of a digital camera can be evaluated using the following four parameters:

  • e-/ADU 
    The sensors found in cameras used for vision applications have pixels that convert incoming photons into electrons. Gain on a CCD /CMOS camera represents the conversion factor from electrons (e-) into digital counts, or Analog-Digital Units (ADUs). Gain is expressed as the number of electrons that get converted into a digital number, or electrons per ADU (e-/ADU).
  • Read Noise 
    Read Noise is the most important reference for measuring a digital camera's performance. Lower read noise usually means better signal-to-noise Ratio (SNR) and better image quality. Read Noise is created within the camera electronics during the readout process as the electrons are subjected to the analog-to-digital conversion, amplification, and processing steps that enable an image to be produced.
  • Full Well 
    The electrons are held in each pixel and are converted into electrical charge, which can be measured to show the amount of light that has fallen on each pixel. The maximum electrical charge possible is termed “full well capacity”. Under the same conditions, such as noise and A/D converter quality, the greater the full well capacity a sensor has, the wider the sensor's dynamic range. As there is a limit to the depth to which pixels can be made, the full well capacity is often proportional to the frontal area of the light-gathering element of the pixel.
  • Dynamic Range 
    It is the ratio between the maximum output signal level and the noise floor at minimum signal amplification (noise floor, which is the RMS (root mean square) noise level in a black image). The noise floor of the camera contains sensor readout noise, camera processing noise, and the dark current shot noise. The dynamic range represents the camera’s ability to display/reproduce the brightest and darkest portions of the image and the number of variations between them. This is technically an intra-scene dynamic range. Within one image, there may be a portion that is completely black and completely saturated.