Monday, April 28, 2008
DPP Solutions: Proper Contrast In Black-And-White
Using your digital tools gives you a level of control that Ansel Adams would have readily embraced
Contrast is critical to a properly printed black-and-white image. There's no color to define and structure a photograph. It all must be done in the monochrome tonalities from black to white.
Contrast is no simple thing. Ansel Adams spends a lot of time talking about it in his classic book, The Print. Early in the book, he makes a statement that's quite appropriate to today's digital photographer, “Some photographers stress extreme black and white effects with very strong print contrasts … [while] others work for a softer effect … their power lies in the ‘seeing' and the balance of values.”
Adams goes on to say that some photographers use contrast for contrast's sake, regardless of the needs of the subject or scene. His point is simply that contrast shouldn't be an arbitrary tool, but that there's an optimum contrast that comes from the vision of the photographer connected to the needs of the image.
Levels And Blacks And Whites
The blacks of a photo (all of the areas of black in an image) have a strong effect on contrast, as do the whites. In most photos, even a small bit of black plus white provides a visual reference for the viewer's eye to establish contrast in a photograph.
My preference is to set blacks and whites using Levels with a threshold screen. Photoshop does have auto features, as well as black and white eyedroppers to set black and white points. This makes the selection of blacks and whites rather heavy-handed, I believe, and doesn't make the photographer look at what's really happening to blacks. While whites are fairly limited in adjustment range, blacks have a large, subjective range that can really change the look of a photograph.
Press Alt/Option while moving the black and white sliders under the histogram in Levels. This gives you threshold screens that show when and where pure black and pure white appear. Usually, it's best to adjust until the whites just appear, unless you're after a special effect with white areas that are devoid of details. Blacks, on the other hand, can handle quite a range. The more black you have in a photo, the stronger the contrast and the effect. Strong adjustments require 16-bit files in order to limit tonal tearing and stair-stepping.
A strong black set this way will mean a dark image. You need to bring out the dark and middle tones so the photo gains some life. Otherwise, it'll look pretty muddy and dark. Curves is the best tool for that.
4. In this image, the first photo has had its contrast changed purely by burning-in areas.
5. Burning-in a photo for contrast starts with a Brightness/Contrast adjustment layer.
With Curves (or the Tone Curve in Camera Raw and Lightroom), you can smoothly and effectively brighten an image so that the blacks are retained, yet the tones that have detail are revealed. This is one place where I find the parametric curve of Camera Raw and Lightroom helpful. This new representation of a curve uses sliders with parameters that photographers know: highlights, lights, darks and shadows.
You can easily change brightness by moving the appropriate slider. One trick that I find useful is to move shadows darker (to the left), darks lighter (to the right), then lights darker and highlights lighter. This gives more contrast in the dark areas and more contrast in the light areas, without making overall contrast too harsh.
In Photoshop, you simply have the traditional point curve. You click and drag on the bottom to make dark areas lighter (move the curve up) or darker (down), and the top to make light areas lighter or darker. Click one point and make the dark areas darker, then another point to make the light areas lighter, and you get a curve that gains some steepness. The steeper the curve, the stronger the contrast.
You can play around with Curves quite a lot to change contrast, but not simply by changing the steepness of the curve. You also have to decide where that steepness occurs: In the bottom area where the dark tones are? Across the main length of the curve to affect all tones? Or mainly in the areas with light tones?
Also, do the dark areas stay the same with a point locked to the midline, while the contrast comes from change to the bright areas? Or does the white area need to be locked to the midline, while the dark areas vary? Each gives a distinctly different look to the image even if the curves have identical shapes.