Wednesday, August 1, 2007
As Simple As Black And White
Shoot in B&W or convert in Photoshop? That is the question...There are many ways to convert a color digital image to monochrome after it has been shot and downloaded. Regardless which postprocessing path you choose to follow, the overall best practice is to shoot RAW format. Doing so will allow more complete control, including exposure compensation and tone curve manipulation. Best of all, all color data remains available.
Whether the image file is RAW, JPEG or TIF, one simple, straightforward way to convert from color to black-and-white is to change the Mode setting in Photoshop to Grayscale (from the menu bar, Image > Mode > Grayscale). You'll be asked if you want to discard color information, and if you click "Yes" that’s exactly what happens. Immediately save the file using a different name to avoid accidentally overwriting the original image and thereby losing the color data forever.
There can be up to 256 shades of gray in an 8-bit image. Each pixel has a brightness value ranging from 0 (black) to 255 (white). The shades (gray levels) of the converted pixels represent the luminosity of the original pixels.
Converting to grayscale provides very limited creative control; however, you can use Photoshop’s Channel Mixer command (Image > Adjustments > Channel Mixer) to mix information from the color channels to create a custom grayscale by specifying the percentage contribution from each color channel.
Another easy way is to use the Desaturate command (Image > Adjustments > Desaturate) to convert a color image to grayscale values without changing the color mode of the image. Photoshop assigns equal red, green and blue values to each pixel in an RGB image without changing the lightness value. One advantage of this method is that you can use the History brush to selectively restore color to portions of the image to combine spot color with monochrome for creative effects.
If you’ve ever experimented with Kodalith Ortho film to create high-contrast back-and-white images, you’ll appreciate the effect produced by the Photoshop Threshold command (Image > Adjustments > Threshold). The Threshold command converts color (or grayscale) images to high-contrast images that are devoid of grays. You can specify a particular level as a threshold. All pixels lighter than the threshold are converted to white and all pixels darker are converted to black.
There are many Photoshop plug-in filters that provide a wide variety of options. Unlike the basic Mode command in Photoshop, plug-in filters include tools that enable you to convert color images to monochrome with extensive control over the outcome. Two of the best are Color Efex Pro from Nik Software and Exposure from Alien Skin.
For maximum control and the most options, try Nik Color Efex Pro. Version 2.0 includes three black-and-white conversion filters, each with its own characteristics. Controls differ from filter to filter, but all allow you to adjust the outcome with incredible precision and choose between Basic or Advanced manipulation. The B/W Conversion filter utilizes a Spectrum slider that allows you to target a particular color range and manipulate how it’s rendered. The B/W Conversion: Dynamic Contrast filter includes a Contrast Enhancer slider that’s used as the name implies. The B/W Conversion: Tonal Enhancer filter has a drop-down Contrast Method menu with three options that provide three separate starting points for contrast enhancement. Color Efex also includes conversion filters that are task-specific: Old Photo, Infrared Black & White, Paper Toner and Duplex Monochrome all allow you to quickly achieve predictable effects without surrendering control over the outcome.
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