RawCA


Version: 0.2
Size:
272KB
Requirements:
No special requirements
Seller:
Wu Yongzheng
Price:
Free
System:
Windows XP/2000/98/NT
Rating:
4.5
License:
GPL

Description - RawCA



RawCA calculates lens` CA from a camera raw file. It works by searching for the largest correlation coefficient of different channels while scaling (stretch/shrink) the channels. RawCA uses raw files instead of jpeg files because CA can be reduced/eliminated by the demosaicing Process which is part of the raw-to-jpeg conversion. Another purpose of this project is to build a database of different lens` CA. GeneRally speaking, CA is a property of a lens, thus CA only depends on lens. However, since the distortion of different color channel is not a linear scaling (It can be a complicated function), and the way I measure CA is a linear ratio, sensor size also affect CA. Consider an image which has Little CA at the center area but strong CA at the corner, cropping the image (reduce sensor size) reduces the CA. Note that only sensor size (millimeter) affects CA, not resolution (mega pixel). As long as the sensor size is the same, resolution doesn`t affect CA, because my measure of CA is a ratio (E.g. the red channel is 0.01% smaller than the blue channel.) instead of number of Pixels (E.g. the red is 2 pixels smaller than the blue at the corner.). I know some lens benchmarks use number of pixels, but I don`t. For exmaple, the same lens can have different CA on a full Frame camera and an APS-C camera, but the same CA on 8MP and 12MP APS-C cameras.



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