Calibration

My Filmscanner (CanoScan FS2710) can produces at highest resolution of 2720dpi an image with the dimensions 2592x3888 px. I usualy scan the negatives/slides with full resolution and reduce the image to half. That leaves me six images of 1296x1944 px with some junk from the film holder at the image border.

Abb. 1: Uncropped scans, each 1296x1944

Abb. 2: Cropped to 1260x1890 pixel

Abb. 3: Converted to pshere with guides