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Slide holding for Scanning - Ohnar and Other Options

Started May 21, 2021 | Questions thread
OP Halina3000 Junior Member • Posts: 32
Re: blade test... and bleed, ghosting, halo or whatever it is called

Bernard Delley wrote:

so you managed to install mtf_mapper and did get results. I assume these numbers were read directly from the mtf_mapper output.

I pre-process the raw file and crop to my chosen region of interest, either center or further out portion of edge. I call the resulting file pix.ppm

linux options (in version 5.15) to produce full MTF output file: edge_sfr_values.txt

mtf_mapper pix.ppm . -q -b --bayer green

Thanks.

I tried to use it on the Canon raw files but that produced an error. Instead I turned off most of the optional modules in Darktable (but kept white balance on) and then exported as a PNG with the original image size.

I used the MTF Mapper GUI and opened each image with manual edge finding. I'm not sure if I did right or wrong but trying it on crops of the etch fret image produced very different numbers. It occurred to me that cropping and scaling could affect the answer so not being sure of exactly how it works I decided to do neither for the time being.

I was also unsure about wether the accuracy of my manual edge marking would affect the result - the width of the marked line seems pretty narrow especially when compared to the width of the more blurry images of the edge.

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