Methods used with SFRplus chart, Light box exposures and Imatest Master

Tests conducted with the SFRplus chart were photographed with illumination from two modeling lamps each at 45 degrees angle. The images were taken as raw files with an Olympus OM-D E-M5 camera at ISO 200. Raw files were converted to high resolution tifs with Adobe Raw Converter. Tif's were analyzed with Imatest Master. Images were analyzed with a 13 region of interest pattern. MTF50 values were summarized as a weighted mean (center - 1.0; part-way - 0.75; corner - 0.25). Central, midzonal and corner MTF50 values were determined as well as distortion and chromatic aberrations with Imatest Master. For each autofocus lens, two exposures were taken at each f/stop and the highest value was used. For the manual focus lens, four photograph series were taken with refocus for each series, and the best value was used in the chart.

Alignment of Camera to Chart: The test chart is on a fixed glass window perpendicular to the floor which is a 12 inch tile floor with grout seams perpendicular to the wall. The tripod and camera are set up next to the window surface to adjust height. Spirit levels mounted to the flash shoe on the camera are used to level the camera. The camera and tripod are pulled back along the tile floor to the working distance using tile grout lines as a reference. Minor alignments are made in the grid reference view finder to align the chart.

Photographs were also taken at infinity of an evenly illuminated white box with aperture wide open than at each full stop until f/8. Light drop off was measured with Imatest. Examples of Imatest results are below.