What are the attributes to consider when selecting a camera and its performance?

We first need to start with some of the basic attributes of the camera such resolution, frame rate, color vs monochrome and interface.  From there, depending on the application, we may look at more advanced attributes such as dynamic range, sensitivity, dark noise and signal to noise ratios.

The basic attributes are easy to understand, but the advanced attributes can be confusing and the data is not easily accessible.  The more advanced information can be found on EMVA 1288 reports from the camera manufacturers when available.  This is a standard which helps provide an apples to apples comparison on key camera sensor attributes.

Allied Vision has done a great job to help understand the attributes by defining the terms and putting them in a graphical format as seen below.  

The following is a graphic to help understand the
terminology along with the definitions  (Courtesy of Allied Vision!)

Definitions are as follows: 

  • Absolute Sensitivity Threshold:  The smallest detectable amount of light.  Expressed in number of electrons.  The point where signal equals temporal dark noise.  This is important to understanding low light performance!
  • Photon Shot Noise:  Signal noise equal to the square root of the incoming photons.  Due to the randomly distributed particle nature of light.
  • Temporal Dark Noise:  Noise when no light is hitting the sensor, also known as read noise.  Due to electric dark current, quantization noise, and other noise sources depending on the specific construction of the sensor and the camera electronics.  
  • Saturation Capacity:  The maximum number of electrons each pixel can hold before reaching non-linear response. 
  • Dynamic Range:  Ratio of maximum signal (saturation capacity) to the minimum signal (temporal dark noise)
  • Signal to Noise at Saturation:  Ratio of the maximum signal (saturation capacity) to noise (photon shot noise).  At saturation, temporal dark noise is insignificant compared to photon shot noise and can be ignored.  

The EMVA 1288 information is available for most cameras upon request.  Contact us to discuss and obtain this information.   

Need help on some of the basics in your camera selection?  We have many helpful blog ports ranging from Calculating camera resolutions to understanding interfaces.  

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