Bridge Reflection

GeminiNeil

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16 Sep 2010 - 9:24 PM

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very tranquil....

DRicherby (Critique Team)

3

17 Sep 2010 - 4:24 PM

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Actually, the bridge is more or less straight — only about half a degree off true, which isn't usually enough to be noticeable, in my experience. Most of the reason that the top hasn't rendered as a horizontal line in the image is that it's in very slight receding perspective. We're not looking quite straight at the bridge but, rather, looking slightly from the right (which is why you can see parts of the insides of the arches, too).

Overall, I think this is a very nice shot, with good colours in the foliage and nice reflections off the calm water. I might try to crop a bit off the bottom to remove the bright reflection of the sky, as bright regions at the edge of the frame often attract attention and pull the eye out of the picture.

One thing to watch out for is the exposure of the sky. In this shot, the sky is actually over-exposed, which has caused it to become rather green. The problem is over-exposure in the blue channel, which has caused the red and green to become more dominant.

Suppose, for ease of explanation, that the true colour of the sky is one part red to one part green to two parts blue. Colours in images are represented as red, green and blue values that must be in the range of 0–255. So, a dark shade of this colour might be represented with red, green and blue values of, say, 30:30:60; a bright version might come out as 120:120:240; note that both of these are in the 'correct' ratio of 1:1:2. The sky here is so bright that the red and green components have been recorded at about 200. This means that the correct rendition of the colour would be 200:200:400 but this is not possible: the sensor cannot record a blue value of 400 because it's too high. All it sees is the maximum allowed value of 255. This means that it records the colour as 200:200:255, which is not in the right ratio any more — instead of 1:1:2, we have something like 1:1:1.3. The result is that the colour recorded by the sensor doesn't have enough blue in it, so appears much less blue than it ought to.

How to avoid this? Set up your camera so it shows separate histograms for the red, green and blue channels, if it can do that. When shooting an image like this, check to see if any of the channels has bunched up to the right of the histogram. If just one or two channels have, there's a good chance that you have this sort of colour distortion somewhere in the image.

I hope that wasn't too technical. If it was, I can try to simplify it a bit, if you want.