standardized photography and color determination

JK
Posted By
Jasper_Keltsch
Mar 13, 2009
Views
516
Replies
4
Status
Closed
hello,

in a study i would like to capture standardized photos of an object that is observed if it’s changing its color.

an example is the yellowing of a paper. to detect this, i need an apparature that guarantees same capturing conditions as light and "film-focus distance".
does someone have experiences with this problem?

second problem is how to determinate the colors correctly and, if necessary, change colors of the following photos digitally to the colors of the first photo.

here i’ve thought of using a test-picture in background that can give me a "mark" how my camera has changed natural colors. will it be possible to customize the color of the test-picture (beside the object) digitally and thus achieve the exact/same color of my object?

with many thanks in advance,

Jasper

P.S.:

am using Windows XP SP3
Pentium 4 3,0 GHz
2 GB RAM DDR2
Photoshop CS4
Canon Eos 450D – Makro Objective with ring-flash

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GH
Gernot_Hoffmann
Mar 13, 2009
Jasper,

reproduction is one of the rare applications for
camera calibration:

<http://www.fho-emden.de/~hoffmann/camcal17122006.pdf>

In the moment I don’t know how to solve the second
task automatically:
‘change colors of the following photos digitally
to the colors of the first photo’.

Best regards –Gernot Hoffmann
RL
Richard Lynch
Mar 16, 2009
Unless I misunderstand what you are trying to do, this should be pretty easy. Use a graduated graycard as a standard. If you pick up something as simple as a paint chit from a hardware store that is supposed to be flat gray, you can measure and make any corrections to standardize in the image even if lighting conditions vary. Of course setting a colorimeter to the chit will be most accurate, and correction can be made easily with curves so they should be nearly dead on (at least for the check points). Standardizing the grays will standardize the rest of the color in the image.

I include discussion about this in several of my books (though not the layers books). But it seems probably easier, more accurate and cheaper than calibrating a camera. But then it may be I am not terribly familiar with camera calibration and how that might affect outcome.

I hope that helps!

Richard Lynch
JK
Jasper_Keltsch
Mar 19, 2009
Thank you for your helpful answers. at the moment im am trying to construct the box and will post it if and how it works.
Mar 19, 2009
Not dead sure, but…

For a thing like this, perhaps it would be better to use any standard calibration target, as it includes more patches of color and they are a referenced standard that have their digital counterparts and can be previously (and repeatedly) measured withe a precision device like a spectrophotometre.

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