03 June 2010

Adjusting colours when scanning film

Most digital cameras have AWB (Auto White Balance). This ensures our pictures are neutral, meaning no visible colour casts. And in digital, we can always use the camera white balance presets or dial the temperature manually in tricky lighting conditions.

Well, in film, it is a different story. Most films are rated for daylight use, around 5000K (the temperature rating), so colour cast is always there, nothing can be done except to put a warming or cooling filter on the lens. However if you are scanning your films, you can adjust the colours accurately in Photoshop using the curve tool.

I use a Plustek 7600Ai film scanner for my scanning needs and although it comes with presets for negative films, colour casts are inevitable. I used to tweak it in the scanner, but adjust each pictures individually took to much time, I need a better solution. I tried the Auto Adjust function in Windows Photo Gallery, which was alright, but the colours seem dull.

Recently, I found out that I can use Curves in Photoshop, you can use the presets, the auto function or the white, grey or black balance dropper tool which adjusts the colours of the whole image based on the selected point that resembles closest to the colour white, grey or black.

Here's a comparison between the colour balance dropper tool and the Auto function.

It is difficult to set the colour balance using the dropper tool, because they gray is often not the middle gray. As seen in this picture the gray in real life it is slightly warmer, so it makes the overall picture slightly cooler. Of course you can tweak the colour balance from here to get the best results but this requires a lot of time, finesse and experience of the trained eye...

The Auto function adjusts the colours that feels just right, just by looking at the green we know that this is a much more balanced picture and it is easy to achieve, just click on the Auto tab in the Curves tool and there you have it...


francescbb@hotmail.es said...

Great blog!! Congratulations!!!


Frank, Barcelona

S.C. Boey said...

A very big thank you... =)

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