GPU accelerated image processing: many image opertions are lightning fast thanks to OpenCL support (runtime detection and enabling). Take advantage of the real power of raw: All darktable core functions operate on 4x32-bit floating point pixel buffers, enabling SSE instructions for speedups. Non-destructive editing throughout the complete workflow, your original images are never modified. Ideally you would put two lights at 45 degree angles from the checkerboard grid, but really you just need it to be bright enough for the camera and the same for each shot. It’s also important to keep the lighting constant and consistent. And if you’re going to shoot JPGs, do not use digital zoom at all ever! The DNG RAW files won’t include your digital zoom level on phones like the Lumia 1020, but if you’re shooting something as JPGs, just remember not to zoom because that will be cropping the image to a different part of where the lens is capturing data and therefore your lens correction profile won’t be correcting the correct parts of the image. You could do this with JPGs or TIFs too, but if you’re interested in lens correction profiles, you’re probably already shooting in RAW format and the RAW data will give you extra flexibility anyway. Don’t forget to set the file format to the camera’s RAW format. It’s most important that you set the ISO level to its lowest number. Set the camera to manual control so that everything stays consistent because you’re going to be taking at least 9 shots. 
I made my frame a little smaller still, but the overlap seemed to be plenty.
You want to place it close enough so that the grid pattern fills between 25 – 50% of the frame. Mount the camera on a tripod that’s just about even with the same plane as your checkerboard print. Don’t print it on glossy paper or put it behind glass since that could cause reflections that will interfere with the checkerboard pattern. It has to be flat in order to work properly. Simply print it out and either mount it to some stiff card board or tape it to a wall. I chose to use the “Landscape Letter – 8.50 In x 11.00 In (Square Print Dimension 54 Pts, Version 9 x 13)” chart. First, you need to photograph some checkerboard prints.
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