A common way to measure dynamic range is to present the camera with an image of a target that on one half is completely black and on the other half perfectly saturates the sensor. A series of neutral density filters that reduce the target image transmission by 50% are then placed between the target and the camera. The number of filters required to make the dark portion of the target indistinguishable from the light portion indicates the number of bits of dynamic range of the camera.

A second method that can be used to measure dynamic range is to measure the camera's signal to noise ratio as outlined in the following article:

Method for determining signal-to-noise ratio (SNR) or decibel (dB) value for PGR cameras.

Given either of these methods, it is easy to convert to and from decibels and effective number of bits as outlined here:

Method for converting signal-to-noise ratio (SNR) to/from bits of data.

Improving a Camera's Dynamic Range

As a camera's dynamic range is bounded on one side by the sensor's full well depth and on the other by the read noise, there are really very few things that a user can do to improve the camera's true dynamic range.

1. Adjust camera parameters to increase dynamic range (Brightness and Gain). The Brightness setting or black level of the camera is effectively the minimum value that any pixel will return. Minimizing the brightness level maximizes the number of levels of intensity available to the sensor to represent the incoming light and thus helps increase dynamic range. In addition to raising the pixel intensities, increasing the camera's gain raises the read noise level. Thus, using the minimal amount of gain that will still allow the A/D to saturate will help maximize the camera's dynamic range.
   
   
2. Adjusting Gamma to improve perceived dynamic range. PGR cameras that implement gamma functionality will allow the user to apply a non-linear response curve. Although changing the gamma does not change the camera's dynamic range, it does change the way the full range of bits is mapped down to 8bpp. This allows the user to map pixels, either near saturation or with very little signal, non-linearly across the grey levels. This effectively changes the user’s perception of the camera’s dynamic range and allows them to see more details in both the brightest and darkest parts of the image. Experience indicates that this is more effective in the darker portions of the image than in the lighter portions. One thing that a user may notice when adjusting the gamma is a grayish film in the resulting image (i.e. image appears washed out). This is generally a result of the Gamma being set too high.
   
   
3. Adjusting Bits per Pixel to improve perceived dynamic range. Many PGR cameras support video modes that provide greater than 8 bits per pixel. While the video mode is generally labeled as 16 bits per pixel (Y16), these images usually have between 9 and 12 bits of useful data. Although using these higher bit depth images will not improve the actual dynamic range, they do provide more resolution across the entire image. This can be useful in cases where users would like to apply custom 'gamma' algorithms.
   
   
4. Filtering the light hitting the sensor. If the camera is black and white, you can add an IR filter, similar to those shipped with color cameras. Refer to Section 2.4 of the Dragonfly Technical Reference for information about the IR filter included with color versions of the camera. We have also had customers have success with a polarization filter.
   
   
5. Increasing the ambient lighting of the scene. Removing spot lighting and increasing the ambient lighting of the scene will reduce specularities and other saturated portions of the image, allow for the most image detail possible.