Posted by
John Clark-2 on
Feb 17, 2016; 9:57pm
URL: http://imagej.273.s1.nabble.com/Color-Correction-for-Underwater-Photos-tp5015660p5015667.html
Only on rare occasions tune into ImageJ issues, as I’m not working in image processing any more…
But… there is in ordinary camera work, either stills or motion pictures, where one shoots some color chart with a certain lighting condition, in order to generate a LUT for ‘correcting’ due to color casts of light.
Photoshop is abysmal for this. For some reason ‘still’ photographers don’t seem to typically do this… they tend to select a ‘lighting’ option on their camera Sun, Tungsten, Florescent, Cloudy… etc. and leave it at that.
If there is any residual cast, they ‘correct’ on the fly using photshop or these days Lightroom widgetry.
In the motion picture world there is a better understanding of this, but even so, creating a custom LUT is sort of a pain. The only tool I’ve found where it is ‘dead simple’, is the Davinci Resolve package from Blackmagic Designs.
The ‘pro’ package is expensive… but fortunately they have a ‘free’ version which has this correction capability.
You could load ‘stills’ in as video clips, use the LUT tool to analyze your chart and it would then develop the custom values required… provided you used one of several industry standard charts.
I use a chart called “Spyder Color Checkr”, but there is support for another chart called X-rite, from X-rite Photo.
Here is a table of ‘chart colors’ to ‘R,G,B’ values:
http://xritephoto.com/ph_product_overview.aspx?ID=824&Action=Support&SupportID=5159One would have to manually place a window over a color swatch, adjust gain, hue, saturation, to achieve that color… like wise for several others… Having never done this by hand, I don’t know how tedious or ‘circular’ this
would be, but at some point one should be able to ‘dial out’ the bluish cast of the scattered light at some depth.
John Clark.
On Feb 17, 2016, at 8:19 AM, klesneski <
[hidden email]> wrote:
> Hi everyone,
> I am doing some analyses of tissue color of corals that I took with an
> underwater camera. I am trying to see if there are differences in tissue
> color among colonies. My idea is to use the color histograms of the selected
> colonies. In each image, I have a color standard card, placed next to the
> coral colony. One of the reasons why we include this card is because red
> light is attenuated with depth, so objects and images appear more blue the
> deeper you are, and the coral colonies are all at different depths. We know
> the RBG values of the color on the card. I am wondering if anyone has
> experience or advice on how I could use this color standard card in ImageJ
> to perform a sort of correction before using color histograms?
> Many thanks,
> KL
>
>
>
>
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