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Why do whites sometimes show a strong bluish cast if photographed in the shadow? More importantly, how to avoid this or remove it in PP?
I had a Common Murre today in MFD distance of the 400F5.6 but tossed them all because the whites had a very strong blue cast. The thought that one might be able to remove this in PP occurred to late...
Thanks in advance. JR
Can't give you 'why' it happens, but as far as trying to stop it
in the future, two words...white balance.
If your're shooting in the shade and your camera has the feature, change your white
balance to cloudy (or the equivalent) and see how that looks.
Now, if you're surroundings keep changing (ie one second shade, one second in sun and
this goes back and forth), I keep my default WB and just change it in post processing
(I use Bibble Pro) so I'm not constantly changing WB (not to mention my mind is more
on the controls vs the birds).
Doug
In shadowed areas, there is no direct sunlight. Light comes from the blue sky, sunlight reflected off of clouds, light reflected from objects in the scene (e.g. trees, grass), and perhaps light transmitted through trees. If the white comes out blue, it is because the main contribution is is light from the blue sky. In complex situations like that, I think it is best to shoot raw and choose the white balance in post processing. If it is obvious that blue sky is the main contributor and you shoot jpeg, choose the shadow white balance.
Roger
Thanks for taking the time to comment. I should have mentioned that I was changing the WB to cloudy or shade or AWB. It was definitely better with cloudy or shade than with daylight but the images still had a strong blue cast.
Then, I am not convinced that the explanation is correct that it is indirect light from the blue sky. First, our eyes obviously don't see the blueish cast. Second, if I am in a forest the whites suddenly don't look greenish, right?
Thx, JR
Well, actually, in a forest whites can look greenish. We had these same issues with film and used color correction filters.Quote:
Originally Posted by John Rain
Our eyes+brain are remarkably good at auto white balance when we see something familiar, and it varies with time (e.g. work in a room with red lights and after a while the red doesn't seem as red). Tungsten light is very red compared to sunlight, and while our eyes+brain adapt well, film or digital will show how far off the color really is.
Personally, I don't like AWB as it is easily fooled. Example: sunsets turn bland.
Roger
Actually, I've noticed that snow in shadow often really does look bluish, sometimes very blue. I know that most people seem to want to remove that blue cast, (or the green one that occurs among high vegetation) but sometimes I wonder why???? After all, that is what it looked like under that condition. Anyone want to address this question? (-:
Anita,
Coarse-grained snow is inherently blue due to absorption of red by water molecules. The absorption is weak so the effect is best seen in when the ice grains are large or the ice is packed together. An additional effect is when very small dust particles are embedded in the ice which increases scattering of blue light (much like why the sky is blue; called Rayleigh scattering). The red absorption by water molecules also explaines why lakes and oceans are blue (excluding when they are green when there is a lot of chlorophyll in the water).
Roger
Thanks for the explanation of why there are blue casts, or green as the case may be. I didnt know the scientific reasons. However, what I was really asking is why we, as photographers, often want to remove that blue-cast in the snow from our photographs? That's how it looked as we photographed it (at least, I see the blue shadows in snow) so if my photograph also captures it, what is wrong with that? We seem to want to remove blue cast in snow, green cast in pictures full of green vegetation; but not necessarily the pink, red, golden casts of sunrises/sunsets. Why, exactly?? :confused:
Perception. If there is a white horse completely in shade with a very blue sky, we see the horse as white if our view does not include white un full sun.. Sunsets, however are usually much redder than a blue cast of a white horse in shade. If the horse is half in shade and half in sun we usually perceive the luminance difference and not so much the blue shade. While most people would never notice the blueish cast. However, if you look close, you can probably perceive the color difference. Sometimes one is faced with a scene that is a combination of sun and shade. This image, for example,
http://www.clarkvision.com/galleries...798_aL4-1.html
has snow in sun and shade, and the snow in shade appears very blue (especially the 30x40 inch enlargements). I did notice the blue snow when I took the picture, but it did not appear as blue as in the picture. Again, perception told my brain that snow is white and made me see the snow in shade biased to white. It was only the contrast of the snow in shadow next to the snow in sun that made the color difference noticeable, but what made seeing that difference harder was the intensity difference.
Roger
The pictures of the Common Murre I took last weekend looked like the snow in the deep shadow in your picture. As if you had put a new blue jeans into a load of white socks and ran it on the hot cycle... That's definetely not how the scene looked like to my eyes and I am still puzzled by the claim that this is solely a perception problem...
But more importantly, how do you fix this in PP - jpg or Raw? As indicated simply switching to different in-camera WB presets didn't solve the problem. Detailed PP instructions would be much appreciated. Thanks, JR
John, I'm not as expert on this as many of the people here are, but one thing I've done successfully sometimes is, select (with magic wand or lasso tool) the area you want to remove the color cast from, and then try reducing the offensive color in one of the color adjustment tools (there are several.) I have even in some cases, just gone to the main saturation mechanism and partially or completely reduced the saturation, maybe adjusting lightness/darkness as well, on the selected area.
Yes, this is how I would do it. Although I do not use the brightness/contrast or color balance tools in photoshop. They are additive approximations to a multiplicative process left over from a when computers were slow. I generally use the levels and curves tools. My digital work flow:Quote:
Originally Posted by Anita Rakestraw
http://www.clarkvision.com/photoinfo/digitalworkflow
Roger
