High Precision SFRplus Target for GL-30E and GLX-30 Lightboxes
-TJ Donegan - Reviewed.com
This transmissive (backlit) SFRplus test chart can be used with the Imatest SFRplus module to measure MTF, lateral chromatic aberration, distortion, and tonal response among other imaging quality factors. The SFRplus module features fully automated region-of-interest detection. The SFRplus chart offers significant advantages over commonly used charts including the ability to produce a map of sharpness over the sensor surface, better measurement accuracy due to the lower contrast, and full support for automated testing.
This target has an active area of 73.8 CM x 42.5 CM (29" x 16.75") with a Bar-To-Bar Height of 385 mm. Please note there is a small gap between the sheets of film when placed on to the lightbox, as is visible in the product image. This gap will not impact measured values or function of the chart in any capacity, it is purely cosmetic.
Megapixel suitability is based on analysis of Modulation Transfer Function (MTF) obtained from a chart image captured using a 1:1 magnification lens (Canon 65mm f/2.8 1-5x macro) and a 6.5µm pixel size sensor (Canon EOS 6D). In order to consider performance throughout the cameras range of expected sharpness, MTF90 (the spatial frequency where MTF is 90%) is weighted at 0.5, MTF70 is weighted at 0.35, and MTF50 is weighted at 0.15. Conversion to megapixels is based on the Imatest Chart Quality Index (CQI) calculation which determines sensor height suitability using the equation 2 * MTFxx (cycles per object mm) * vertical chart height (mm), where xx is 90, 70 or 50. Megapixel suitability calculations assume that (1) the lens is of high quality, (2) that the chart fills the vertical field of view (vFoV) of the camera system, and (3) that the sensor aspect ratio is 3:2. For 16:9 aspect ratio sensors (with pillarboxed framing, if applicable), multiply the megapixel suitability by 1.185. For 4:3 aspect ratio sensors (with left/right sides of chart cropped), multiply megapixel suitability by 0.889. Charts can be suitable for significantly higher megapixel counts if the minimum resolvable feature size of the lens is larger than the pixel size or the chart fills less than the full sensor vertical field of view.