Luminous Landscape Forum

Raw & Post Processing, Printing => Digital Image Processing => Topic started by: lumines on June 02, 2013, 09:31:18 pm

Title: Colour cast (eg Gimp)
Post by: lumines on June 02, 2013, 09:31:18 pm

Camera lens; large speck like dust; gives a slight center color cast on raw images.
(cast is hard to detect or not so obvious; noticeable in the resulting images)

Best ways in removal; so as to restore back original color?

Shoot against a black or dark background at all focal lengths to determine size and color of speck cast?
Then apply counter numerical filters or certain tools in removing the cast then somehow adjusting the area colors back to original?
Or another alternative method?

Title: Re: Colour cast (eg Gimp)
Post by: tho_mas on June 03, 2013, 02:34:14 am

here's how to shoot a "white reference" ("lens cast calibration" / "LCC"): http://support.phaseone.com/KBFiles/2118/1/LCCWin.pdf

and here is how to remove color cast in Photoshop (should be similar in applictions featuring layer modes):
http://www.luminous-landscape.com/forum/index.php?PHPSESSID=3a6d659c788f06c5f1a697daf7f3dd5d&topic=33683.msg276114#msg276114

Title: Re: Colour cast (eg Gimp)
Post by: Bart_van_der_Wolf on June 03, 2013, 03:21:29 am

Quote from: lumines on June 02, 2013, 09:31:18 pm

Camera lens; large speck like dust; gives a slight center color cast on raw images.
(cast is hard to detect or not so obvious; noticeable in the resulting images)

Best ways in removal; so as to restore back original color?

Hi,

As indicated, an LCC (Lens Cast Calibration) shot will allow to address the issue with the best quality.
When you shoot Raw files, you can also use RawTherapee (http://rawtherapee.com/) to do it automatically for one or many files with the "Flat field" functionality.

Cheers,
Bart








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