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Robert D Feinman

Seeing into the Shadows

Modern imaging systems can capture a wider range of brightnesses than ever before. Modern color negative films can capture upto 12 stops while some digital cameras have similar capabilities. Recent cameras also allow for multiple exposures which can be combined into one full-range image in post processing.

Here is a typical wide range image of the Indian ruins in the Canyon de Chelly, Arizona.

Notice in the center there are some building which are almost white. Holding onto highlight detail here is always a problem. To make things worse immediately to the left there is a cave in deep shade. A wide range image indeed!

Full range
Full Range Image

This is the histogram of the above image. Notice that there is a slight amount of clipping at both ends of the scale. This is a result of adding a simple curves layer using the auto option with clipping set to 0.1% for both the shadows and highlights. This expands the original film scan to use all the values.

The dark clipped area is in the shadows on the rock in the lower left and is not important.

The highlight clipping is in the central building and may be a problem later on. By leaving the curves adjustment as a separate layer we can fix this later.

Histogram
Full Range Histogram

A typical photofinisher will produce an image similar to this. The adjustment sets the black clipping at 5%. This produces the kind of depth of color and contrast that most people are used to.

The overall lowering of the values also eliminated the highlight clipping and makes the colors look richer.

Five Percent Shadow
Five Percent Shadow

After This is the histogram of the image above. Notce that large spike at the left edge which indicates all the values which have been lost in the cave and rock.

Notice also that the clipping of the highlights on the right side has been eliminated.

Most people would find this an acceptable compromise. But we can do more if we wish.

Five Percent Histogram
Five Percent Histogram
This is a mask created by selecting the shadows in the image with the selective color tool and inverting the selection. The large white area is the interior of the cave. As we can see very little of the image will be affected when we make some adjustments using this mask.

Only the clear areas will be fully modified.
Shadow Mask
Shadow Mask
This shows the mask layer with the maks applied in the layers palette. We used another curves layer to boost the brightness of the shadow area.

This allows us to "see" into the shadows. If we were viewing the scene we might have to shade our eyes to see this detail. But in our mind's eye we probably aren't aware of how dark the cave is.
Shadow Mask Layers
Shadow Mask Layers
Here is the result of brightening only the shadows. I used only a slight amount so that the deepest part of the cave is still black, but if you look closely you can now see that there are other ruins withing the cave as well. The same thing is true in the smaller cave to the right.
Open Shadow
Open Shadow
Most people would still find the brightest parts of the image too light. The white building is still washed out. If we wish to print this image having values above 235 or so usually leads to a lack of any texture.
To correct this I modified the original curves 1 layer and lowered the highlight point from 255 to about 240.
In addtion I added a hue/saturation layer and boosted the saturation of just the reds by +8. This makes the rocks look closer to how they appeared when I took the picture.


Saturation Layers
Saturation Layer
Here is the final version. There is still an impression of a high contrast scene, but more detail is preserved than in the standard version.

Here are both side by side for your comparison. Neither is more "correct", but being able to see into the shadows opens up new aesthetic options. With the popularity of high contrast, punchy images these days such choices may seem flat, but maybe we have just been pushed in one direction by the commercial needs to get their images noticed in a visually cluttered world.

You decide.
Increase Saturation
Increase Saturation
Five Percent Shadow
Five Percent Shadow
Increase Saturation
Increase Saturation

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© 2007 Robert D Feinman