Chroma Decimation in Digital Video Signals

Chris Bore wrote:
> It is suggested that natural scenes tend in fact to show less
> high-frequency variation in color than they do in luminance. 'Natural'
> being hard to define but still being a very small subset of all
> possible images that one could imagine.
> 
> Similarly, 'natural' images tend to show more horizontal and vertical
> lines than they do slopes, although this is not a very robust
> suggestion.

In the eye, at least, this depends on how one cocks ones head.

> And natural scenes tend to show more neutral colors than they do
> extremes.

http://users.rcn.com/jyavins/woodpecker1.jpg looks pretty natural to me.

> The logic for the human eye's having lower color than luminance
> resolution is then turned back-to-front: the eye evolved that way
> because nature is in fact that way.

Maybe. And maybe it was a worthwhile tradeoff for other reasons.

> Many images can be thought of, found in nature, and produced, that
> contradict these suggestions - but often, such images turn out to look
> 'striking' - that is, they stand out just because they do look less
> natural.

True! (like woodpeckers and orioles).

   ...

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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>> Similarly, 'natural' images tend to show more horizontal and vertical
>> lines than they do slopes, although this is not a very robust
>> suggestion.

>In the eye, at least, this depends on how one cocks ones head.

Yes, and I swear that if I look at a scene with horizontal lines,
holding my head at a slant, then I can see those lines less well. :-)

>> And natural scenes tend to show more neutral colors than they do
>> extremes.

>http://users.rcn.com/jyavins/woodpecker1.jpg looks pretty natural to me.

I should have said 'neutral tones' rather than 'colors'.
But woodpeckers do look striking, don't they?
Maybe that's because they are less natural than other natural things?

I guess here we can get onto the difference between using neutral tones
(Leonardo da Vinci) and using highly saturated tones (some of
Michelangelo's works). And those two (Leonardo and Michelangelo) almost
came to blows over this same issue. :-) It's not a new debate.