Vignette and distorsion correction (for older cams) - Feature Requests - CHDK Forum
« previous next »
Pages: [1]   Go Down

Vignette and distorsion correction (for older cams)

  • 1 Replies
  • 4050 Views
*

Offline toinech

  • ***
  • 105
Vignette and distorsion correction (for older cams)
« on: 20 / January / 2012, 19:43:07 »
Advertisements
Some newer cams apply vignette {and distorsion correction}.
Not sure which one does?
Is it possible to do such correction (at least vignette which seems to be the low hanging fruit here) with older cameras?
Or it is too much processing.
Procedure seems to be simple:
1. Aperture, Focal length => vignette profile (most likely an attenuation factor based on radius)
   Vignette profile is camera dependent - possibly tables or math functions that interpolates the actual vignette of the lens
2. Radius is function of x, y and some reference point x0, y0 (most likely center of the sensor)
3. Multiply the pixel value brighness by reverse of attenuation.

Toine
Logged
*

Offline reyalp

  • ******
  • 14128
Re: Vignette and distorsion correction (for older cams)
« Reply #1 on: 20 / January / 2012, 20:33:04 »
Vignette seems like it should be possible, though probably slow. reverse_bytes in optimized assembler takes a significant fraction of a second. If you can figure out how to program the image processing of Digic, that might be a different story.

You could also do this with a flat frame but this would be even slower. I suppose applying flats could be a menu operation like sum, average and subtract.

I'm not really sure of the value, I would expect most people concerned with this to have an extensive workflow on their PC. Assuming you use raw/dng there would be no quality advantage to doing it on the camera.

Distortion correction seems like it would be harder.
Logged
Don't forget what the H stands for.
Pages: [1]   Go Up
« previous next »
 

Related Topics


SimplePortal © 2008-2014, SimplePortal