{"id":282,"date":"2013-01-18T17:15:15","date_gmt":"2013-01-18T16:15:15","guid":{"rendered":"https:\/\/www.skeptic.de\/blog.multi\/kiwi4\/?p=282"},"modified":"2023-09-23T19:59:17","modified_gmt":"2023-09-23T19:59:17","slug":"purple-picture-processor","status":"publish","type":"post","link":"https:\/\/leetraynor.com\/blog.multi\/kiwi4\/?p=282","title":{"rendered":"Purple Picture Processor"},"content":{"rendered":"
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Dersch\u2019s A and B vs. Zoom<\/p><\/div>\n

It seems like we\u2019ll be waiting some time for the camera that takes the view you saw and makes it into a picture on its own. On the way to this goal a number of problems turned up that were solved on the computer. Low dynamic range<\/strong> (high contrast) was improved by bracketing and enfusing; barrelling<\/strong> (radial distortion) by determining the Dersch coefficients (left) and applying a counter-distortion; and chromatic aberration <\/strong>by measuring sets of aberrations (below right) and remapping the colour channels so that they now matched each other. What we might also like to do is process RAW images, save copies of the originals, both as JPG and in a sturdier format such as PNG. And while we\u2019re moving the formats around, taking care that the EXIF data gets transferred too, perhaps a little extra data could be included. Then some postprocessing like Advanced Tone Mapping. And finally, thumbnailing and sharpening so that the images can be experimented with. Oh dear, it seems like Christmas is rather early this year. <\/p>\n

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Chromatic Aberration vs. Aperture<\/p><\/div>\n

Enter the Purple Picture Processor<\/strong> – all my own handiwork. Since these tasks have to be done in a set order, the secret was in establishing that order. This took a bit of huffing and puffing, and, like tramping, a couple of wrong turns and starting back from the last known working values, but in the end it worked out fine and has proven itself on the road, during the Alpine Crossing of 2012. After all, when do you want to process all of those photos? Even the simple stuff will ruin an evening, and I seem to recall that the repeat-exposure brackets from White Island (almost 800 photos in all) took days to run through aligning and enfusing. There\u2019s one place I\u2019d rather be after a day photographing, and it\u2019s not in front of the computer.<\/p>\n

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Chromatic Aberration vs. Zoom<\/p><\/div>\n

I won\u2019t go into the technical details here, but suffice to say that it is not a very complicated, or even long, program (the complete code weighs in at just over 500 lines, including a new-fangled status reporter that indicates what the computer is up to at any time). When the test of tests has been passed, I\u2019ll take the technically interested on a tour of PPP\u2019s insides.<\/p>\n

This is what automation is for, and it opens up wide vistas, in every sense of the word. It\u2019s been a long journey from a inexpensive point&shoot camera to an instrument capable of seeing as well as, or better than, the eye. The learning curve was steep at times.<\/p>\n

But now seeing the world with new eyes, it\u2019s getting time to photograph the South Island anew\u2026
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