Digital SLR Camera Online Target Resolution Calculator

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Helps surveillance photographers determine the optimum lens for current model Nikon and Canon dSLR cameras

A new online calculator is now available to help surveillance photographers select the best combination of lens and digital SLR camera model. Because the calculator includes array and pixel size data for the detectors found in current model Nikon and Canon dSLR cameras, the tool can calculate the projected pixel size at a certain range and the pixel and lens fields-of-view for a camera and lens combination. In addition, for a given object size, the calculator estimates the maximum distance for detecting, recognizing and identifying objects of interest. With this calculator, photographers now can estimate the desired range performance or determine what lens focal length is required for the camera that is being used to achieve the range objectives necessary. The effectiveness of the calculator is further described in a comprehensive white paper entitled: “Digital SLR Cameras – What’s new for Military Photography” located at

This dSLR Camera Range Calculator enables the user to easily make estimates regarding maximum range performance when using various camera platforms. It is important to note that these estimates assume that range performance is based solely on image quality yielding a method of estimation that’s simple to implement. The estimates are based on the object size, distance, camera objective lens and camera detector parameters. Object brightness, reflectivity, atmospheric conditions and other factors are not considered. In this regard, the object size and focal length of the objective lens are variables to be entered by the user.

The calculations used in this tool are based on the “Johnson Criteria” which were developed many years ago by John Johnson, a scientist at the US Army Night Vision Lab (Night Vision Electronic Sensors Directorate). Johnson was working to develop methods of predicting detection, recognition, and identification ranges and worked with volunteer observers to identify scale model targets under various conditions. His experiments produced the first empirical data on perceptual thresholds. The so called Johnson Criteria has been the basis for many models that predict performance of sensor systems under different environmental and operational conditions.

To view and use this tool, visit

Company Background
Headquartered in Fairfield, New Jersey, Electrophysics, also known as Sofradir EC, Inc., is a member of the Sofradir Group of companies since December 2008. The company develops and manufactures advanced night vision systems for photography and videography as well as thermal imaging, near infrared systems for use in a host of imaging applications.

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