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Blue-atmospheric haze

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  #1  
Old 10-14-2003, 07:32 AM
flight1 flight1 is offline
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Blue-atmospheric haze

How can I correct the blue-atmospheric haze seen in many of the photos I took of the Grand Canyon on a recent trip there?
Thanks for any help you can give me. Tom
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  #2  
Old 10-14-2003, 09:48 AM
Stephen M Stephen M is offline
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Tom, the problem is the human eye auto adapts and neutralises the white/black/grey points in the image - while the camera faithfully records the scene, blue haze and all.

The solution, simply setting endponts and neutral tones - in this case the highlights and neutrals were pretty good...it's the shadows that are the problem, with the blue channel being the major issue.

This correction was done with the simple levels/curves eyedropper tools in Photoshop.

I chose a dark area of the cliff in the foreground as the shadow point.

Some sharpening was also applied.

More can always be done, this is pretty quick if you have a lot of images to process, but not an automated (fully) process.

Some very good links on colour correction and the theory behind the moves (image evaluation etc) can be found here:

http://members.ozemail.com.au/~binar...V_links.html#C

See attachment below for the correction example.


Hope this helps,

Stephen Marsh.
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File Type: jpg yavapi-2-quickfix.jpg (89.3 KB, 80 views)
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Old 10-14-2003, 12:40 PM
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KenB KenB is offline
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I used a curves adjustment layer set to luminosity mode and adjusted the individual color channels seperately Then I bumped the red value up slightly with a hue/saturation adjustment layer.



Ken
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Old 10-14-2003, 01:43 PM
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catia catia is offline
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Ken,

I am confused. I don't know how to set luminosity mode for curves. Did you mean you used color balance with preserve luminosity selected?

Thanks,
Catia
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Old 10-14-2003, 02:21 PM
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KenB KenB is offline
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Quote:
Originally posted by catia
Ken,

I am confused. I don't know how to set luminosity mode for curves. Did you mean you used color balance with preserve luminosity selected?

Thanks,
Catia

The way I do it is use a curves adjustment layer, ok the curves adjustment without making any adjustments and on the curves layer set the mode to luminosity, then double click on the curves layer to go back inand make your adjustments. Doing this, the colors won't shift. Hope I explained this well enough.


Ken
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Old 10-14-2003, 04:38 PM
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jch71566 jch71566 is offline
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Wow, what a challenge!

I came to the same conclusion as Stephen that the shadows suffered the most here. I tried several fixes with histograms and levels, with some good success. However, I tried one experiment that really popped in my eyes:

Layers (from the bottom):
1) Original Image
2) Copy of original's Blue Channel, colorized to Blue/Cyan (Hue=210 from 360), Opacity~30%, Blend=Difference
3) Adjustment: Levels to taste

This was a happy accident. I indended to subtract out pure blue, but miscalculated the hue. When I went back and did it pure blue, the results were poor. Getting rid of the green seems to help.

Thanks,
Jeff
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File Type: jpg nobluecanyon.jpg (28.1 KB, 63 views)
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  #7  
Old 10-14-2003, 06:25 PM
Stephen M Stephen M is offline
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The human eye sees the shadows as a deep _neutral_ so that is what we should probably correct for. The camera sees the shadows as blue. We need equal values in the R, G and B channels somewhere in the shadow section. This can be done by hand or the eyedroppers - it does not really matter.

If an image should have white/neutral/black points and it does not - chances are it can look a lot better by forcing these key target zones to be true...the rest of the image often snaps into place (to some degree).

But without removing blue (adding yellow) from the entire tonal range of the image - it will still suffer, as this is the major problem (lack of range/contrast and impossible colours for key memory points on the image).


Stephen Marsh.
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  #8  
Old 10-15-2003, 08:11 PM
flight1 flight1 is offline
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Thanks for the help, guys. Your results are great but I'm interested in the fact that there are differences in the color casts in the different images. The Grand Canyon and the whole area from Monument valley to Bryce Canyon is composed of that reddish rock. It sometimes seems imposible that the rock could be that color, especially at sunrise or sunset. Tom
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  #9  
Old 10-15-2003, 09:44 PM
mead mead is offline
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I have tried this on mt. pics and it works well.
Unsharp mask
amt. 30 radius 60 threshold 1

Learned this at dpreview forums. I think Isabel posted it.

Other settings to try USM Amt. 50 Radius 100 threshold 2

Just have to play with the settings for different pics.
This is at USM 30 60 1

hope that helps
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File Type: jpg grandcanyon30-60-1.jpg (95.9 KB, 47 views)
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  #10  
Old 10-15-2003, 09:49 PM
mead mead is offline
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and this one with the USM at 50 100 2
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