acknowledgements for ansi/nist-itl 1-2011 - NIST Visual Image ...

ANSI/NIST-ITL 1-2011 - UPDATE 2013 DRAFT VERSIONexamined, the maximum difference between the means of any two of the RGB componentsshall not exceed 10.E.3.5ExposureWhen capturing images using digital cameras, the exposure should be such that the image is asbright as possible without introducing any clipping of the highlights. With most digitalcameras, this can easily be checked by examining the histogram 197 associated with the image.Most modern digital cameras have sophisticated metering systems that should ensure that aproperly exposed image is always captured once the camera and lights have been correctly setup.E.3.6No saturationFor each patch of skin on the person’s face, the gradations in textures shall be clearly visible. Inthis sense, there shall be no saturation (over or under exposure) on the face.E.3.7No unnatural color or “red-eye”Unnaturally colored lighting (e.g. yellow, red) is not allowed. Care shall be taken to correct the“white balance” of image capture devices. The lighting shall produce a face image with naturallooking skin tones when viewed in typical examination environments. “Red-eye” is notacceptable.E.3.8No color or grayscale enhancementA process that overexposes or underexposes a part or all of a color or grayscale image forpurposes such as beauty enhancement or artistic pleasure is not allowed. The full spectrumshall be represented on the face image where appropriate. Teeth and whites of eyes shall beclearly light or white (when appropriate) and dark hair or features (when appropriate) shall beclearly dark.E.3.9Distortion and angle of viewUnnatural radial distortion of the camera lens, resulting in a diagonal angle of view ofapproximately 20 to 28 degrees, shall not be allowed. Fish eye effect, a type of distortion wherecentral objects of the image erroneously appear closer than those at the edge, typically resultingin what appear to be unusually large noses in the image, is not allowed. While some distortionis usually present during portrait photography, that distortion should not be noticeable byhuman examination. For a typical photo capture system with a subject 1.5 to 2.5 meters fromthe camera, the focal length of the camera lens should be that of a medium telephoto lens. For35 mm photography, this means that the focal length should be between 90 mm and 130 mm.For other negative formats/sensors, the recommended focal length is 2 to 3 times the diagonalof the negative/sensor.197http://www.photographyreview.com/histogramguidecrx.aspxMay, 2013 DRAFT VERSION UPDATE 2013 Page 473