ABSTRACT

When analyzing a digital system the accepted method for obtaining input data is to use the ISO 14524 target. The ISO has established a standard (ISO 12232) that outlines the required

method for making an exposure when the resulting data will be used in a sensitometric study. The illumination should be either CIE illuminant D55 or tungsten illumination having a color temperature of 3,050 K. The ambient temperature of the area where the exposure is made should be (23 2)º C with a relative humidity of (50 20)%. The camera white balance should be adjusted so that the signal levels for the RGB are equal. That is, when the exposure is made, the white patch in the target should have equal values for the red, green, and blue digital counts. The IR blocking fi lter should be in place. In most cameras, this cannot be removed. The shutter speed shall not exceed 1/30 second. If possible, no compression will be done to the image prior to saving it on the camera memory card. All other camera setting options should be set to the manufacturer’s default settings. Finally, when making the exposure, the digital count values for the lightest patch on the target shall be as close to the maximum digital count available for the camera without clipping occurring.