Sunday, 28 November 2010

Exercise 13: Managing colour

For this exercise I needed to find 2 or 3 images that had a significant colour cast and to correct it, taking care to retain a reasonable colour and colours that would be expected ie a grey surface would remain grey. I needed to make sure that at least one of these images contained a known grey surface ie concrete, steel, aluminium , asphalt, thick clouds and shadows on white.

As I had shot these images in JPEG+RAW I could experiment with adjusting colour cast with both. The first thing I noticed was that the colour cast was more obvious with the original jpegs.

The first image I chose has a yellow cast, although admittedly it isn't that strong a cast but enough that the skin tones are rather sallow and the blue sky appears a rather washed out murky colour. This was also an ideal image to choose as it has several surfaces that I could select as my grey point.

Original Jpeg file

Original raw file
When working with the JPEG image the white balance control was not available so I chose to use the grey dropper available through the Curves window. The steel handrail gave the best results when using the dropper but even so this made the image shift a little too far.

I then used different techniques, different layers, changing the opacity and experimenting with the targeted adjustment tool, to obtain a satisfactory result.

Adjusted Jpeg
Working with the RAW file gave me access to finer control of the white balance. I experimented with the presets but found none really matched the result I was looking for so I adjusted the white balance slider using a Custom setting. I then altered the hue and saturation very slightly.

Adjusted RAW file
 Looking at the end results they are pretty close together and any differences could be due to over correction with one of the tools/techniques used. I am happier with the RAW conversion as the white buildings in the background do not appear to be as stark a white. I still need to become more conversant with the adjustment tool in RAW to fine tune any local adjustments. I still prefer to do this via layers in Photoshop.

The second image has a distinctive blue cast. Once gain the colour cast is more obvious in the JPEG file.

Original Jpeg file

Original RAW file
Once again I used the grey dropper tool and layer adjustments/ targeted adjustment tool to correct the image. The image appeared to be ok on my screen but now it has been uploaded I think it could have been brightened a little more as the snow now looks rather grey.

Adjusted Jpeg

Again I chose to adjust the whte balance slider and alter the hue. The difficulty I experienced with this image in RAW was keeping the colour of the bears correct, I tried to do local adjustments in RAW but they were not very successful. In practise I would have then opened the image in Photoshop and completed the adjustment with layers, however as this task was about the comparison of managing colour with either RAW or JPEG I left it as it was.

Adjusted RAW

In conclusion I would still choose to do my main colour cast/white balance adjustments in RAW, once the techniques of all the tools have been mastered it gives more fine-tuned, subtle results than working with jpegs. Having said that at the moment I obtain better results when mixing both RAW, converting to a TIF and doing fine-tuning with layers and layer masks.

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