dodgy filters or normal - colour separation in histogram

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Lawrence
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my new tripod arrived last week so went for a quick play yesterday, plonked it on a hill top and tried all sorts of things (unfortunately I didn't try to check the ISO, still had it on 800 so noisey mess on everything :bonk:)

got the pics home and I notice that SOME but not all shots have a very pronounced separation of red green and blue peaks at the right hand of the histogram corresponding to the sky.

Is this normal or is it indication of a problem such as:
- bad lens coating
- dodgy skylight 1B filter (25 years old some of mine, all were cheapish), (or is 1B just the wrong choice)
- unwanted colour in the graduated ND filter (Kood filter)
- operator stupidity :nuts:

anybody seen this before? :thinking:

I'll now have to go out & do some tests to isolate it but some pointers could be helpful :shrug:
 
sample :

separation.jpg
 
OK I just quickly picked one, I know the foreground is a mess, composition is appalling etc etc, but I've already played with levels in most of the decent ones
 
It really depends on the colour, they'll only be lined up if the colour is a perfect shade of grey. If you took a picture of something red then the blue and green channels wouldn't show very much at all.

As to why some shots showed this and others didn't - were they all of the exactly the same thing with all the same settings, esp. white balance?
 
From that example, I wouldn't worry. Looking at the shot, it looks like the sky has much more red in it than blue, which would explain the colour separation on the histogram. Like pxl8 says, they would only match perfectly if it were all grey.
 
thanks for your comments,

I've been busy fiddling with the shots trying to work it out.

all were done with auto white balance

most of the shots included bright sun shining through clouds (and possibly a rain patch) in the distance, and that is where the red tint is strongest

I can get the shots to produce a neutral sky colour near the sun by pippetting the clouds in the bright area as my white balance, the darker overhead clouds then get a bluish tinge (thus proving its not an issue with lens or filters) and the dark foreground ground loses its red.

I therefore conclude that I've got a conflict in white balance generated by the sun being relatively low through cloud and throwing a lot of red into the mix locally in that portion of the sky. AWB is throwing a wappy as it doesnt have a clear neutral reference area and different bits of the shot are singing different songs (metaphorically).

Does this sound plausable?
 
Auto WB is most likely the cause, it works in a general way but rarely nails it and will vary from shot to shot.
 
I think I was pushing my luck (again), I managed to drag this shot into something close to respectable by twiddling the knobs, I can't remember if this one had the ND grad filter, I suspect not (2nd shot of the day)

This shot though shows where it was going wrong, look at the left side through the tree, compared to the rest of the landscape

After this shot I repositioned and was zooming in on the brightly lit area that is shown on the left of this shot behind the tree. It was only a play session and I wanted to see if I could even out ground exposure with getting pretty clouds so after this I began shooting tight in to the bright area as there was some nice bands of sunlight and dramatic edge lit clouds.

However I reckon this shot demonstrates the colour balance variations in the area and this is after I played with the levels to even it out a lot:

IMG_1602a.jpg
 
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