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Since the reds are from direct specular light and the blues are from indirect diffuse light, the intensity of the reds (naturally occurring) is greater than the blues. For the piece, I had to push the blues harder than the reds to get them closer together.
I left the WB, as shot @ daylight, 5500K and worked mostly from saturation. I'll likely experiment with some WB masking and a few other methods to try and get the vividness to the colors, with possibly a little less "overcooked" effect.
My goal for this piece is to clearly illustrate (hence the saturated colors) the concept of how our ambient lighting is not really a single WB temp as we are inclined to think. But rather act as two separate sources of lighting ... a cool, indirect, diffuse overhead sky (which acts as a cyan-blue fill light) and a warm, direct, specular sun (which acts like a yellow-red key light).
When the two of these sources are most "aligned" (say at midday), they balance/blend with each other in such a way to yield the perception of a more nearly homogenous temperature, yet the shadows (i.e. fill only) still are cooler in the absence of the warmer key light (i.e. direct sun). As the day progresses ... the angle of light being received from the overhead sky remains global / omnipresent. Meanwhile, the angle of the light from the direct sun continues to change.
The more "misaligned" these two become ... the greater the distinction / separation that occurs regarding the color temps ... i.e. the blue shadows become stronger when a subject is WB corrected for the warmer key light, or the subject is warmer when the cooler shadows/cast are globally neutralized.
I realize this isn't rocket science or anything "new under the sun" ... but I find it important relative to understanding why we have difficulty getting good WB and eliminating color casts at varying times of the day. For some subjects, this isn't much of an issue. But for those subjects that are both highly reflective, and are dimensionally reflective (waterfalls, faces, wedding dresses, cars, snow covered mountain tops) such that they can reflect from perpendicular angles ... the "separation" of the warm and cool becomes more readily noticeable.
As with any lighting temp(s) ... it is a matter of choice, preference, control ... as to whether you want to harness and enhance those colors/tones, or you want to correct/neutralize them. But, imo, it is important to understand their existence before you can understand how to better utilize them to achieve your goals.
Ben's recent post of the classic Teton shot shows a similar capture of the two separate light sources in play. The cedars are receiving the warm sidelighting that dominates over the influence of the blue tones from the sky, while the lake is reflecting the cool tones of the overhead sky in the absences of reflecting the warm key light. In this regard, the two reflected light source orientations are perpendicular to each other ... yielding the most distinct separation possible. Also, we can see the evidence of the gradient in the lake colors as the AI=AR changes (similar to the tracks).
Meanwhile, the angle of the Tetons are reflecting somewhere between the two extremes and is reflective of a more homogenous / "white" (blended warm & cool) light that exists where both sources overlap.
In a similar manner, the donation box from Scott, shows the difference in the reflective surfaces as the top surface renders a purplish colored rust, while the front face renders a "normal" colored rust. The top surface is being influenced by the blue overhead fill, whereas the front surface is reflecting much less (AI=AR) of the overhead sky. Of course, if we were to walk up to the box and look at it ... we wouldn't see the purplish tones as readily, thanks to our sensory adaptation.
The thing I most like at the RR Track piece is where the tracks are "white". The track of course is a constant, continuous "color" ... IF and only IF it is reflecting a continuous "color" light source. For me, this clearly illustrates both the separation of the two light sources, as well as shows the effect of where the warm & cool light sources combine to create a "white" light.
So ... what's the point to all this
Well, in the land of the "micro-nit" ... I find that having things like blue highlights or a green cast in a woman's hair to be less than flattering. Wonderful warm, glowing skin tones from our "golden hour" sidelighting are nice. But with that reduction in power from the key light, comes an increase in impact from the fill (blue overhead). So ... when you are trying to figure out how to fix one, without killing the other, understanding that it as though you have lit your subject with a red key light and a blue fill light can help you determine how to proceed to achieve your goals of correction or enhancement ... whichever they be ... likely needing to be selective in nature, rather than a global WB adjustment.
There, I said it ... and hopefully, the piece shows it.
Edited on Sep 07, 2012 at 01:28 PM · View previous versions