Wednesday, May 23, 2007
The Ultimate Black & White
New technology and techniques are giving rise to the ability to create the best black-and-white images ever
Taking The Local
Five different methods of converting from color to black-and-white have been outlined so far. Each has its strengths and may produce an optimal result for some images. However, each of the methods have one significant limitation—they're all global conversions from color to black-and-white; none of the above methods are capable of addressing the local needs of an image. For the ultimate control over a conversion, you need the ability to apply local adjustments to the conversion process.
This next method may seem a bit complex, but the basic setup and process easily can be automated by creating an action to produce the basic layered results. To demonstrate this approach, I'll switch to a different image—one that will be used for the second part of the article, outputting black-and-white.
This procedure starts with a standard RGB color image (Figure 12). The first step is to duplicate the color image and then immediately convert the duplicate to a grayscale image.
You'll end up with both a color and grayscale version of your image open at the same time. The next step is the most critical to understand—you'll need to copy the color channel from the color image and paste it as a layer in the grayscale document. This concept of using a color channel as a grayscale layer is the basis of this method (Figures 13a and 13b).
The color document is the active image window. Target the individual color channel—in this case, the blue channel—select all and then copy (Figure 14).
Next, click on the grayscale document to make it active and simply paste. This will paste the image data from the original color file's individual color channel into the grayscale document (Figure 15).
Go back to the color document, activate the green channel, then activate the grayscale document and paste. You'll end up with three separate channels pasted as layers in the grayscale document.
Ideally, you should rename the layers in the grayscale document to represent the channels from which the layers originated. If you were to adjust the layer opacities of the individual grayscale layers, you could arrive at your own special blend of the base color-to-grayscale conversion (Photoshop's default), plus the red, green and blue channels derived from the original color image. This would still only be a global conversion relying on layer opacities. To further employ this method, you must use layer masks to locally adjust the individual opacities of the red, green and blue layers.
By holding down the Alt/Option key and selecting the Add Layer Mask command, you easily can add a Hide All layer mask to each of the grayscale layers.
By targeting the individual layer mask for each layer, you can paint in your own custom localized blend of red, green and blue layers to achieve an optimal black-and-white conversion.
In this result, the individual layers have had layer masks applied and adjusted to produce an optimized color-to-grayscale conversion, and the result has only relied on the different native color channel information of the original color file—no image adjustments, such as levels or curves, have been applied (Figure 16).
Why do I keep the color image open even after producing the layered black-and-white image file? Well, once the image has been reduced to grayscale, one powerful tool for making selections based on color—Color Range—has been rendered relatively ineffective.
By keeping the color image open, I can use Color Range to make a specific color-based selection and drag the active selection from the color image into the black-and-white image (hint, since the images are exactly the same pixel dimensions, once you start to drag the selection over, hold down the Shift key to register the selection in the exact spot in the grayscale image) (Figure 17).
Here the Color Range selection has been dragged into place on the grayscale image, the blue channel layer mask has been targeted, and the area of the purple flower is being painted in (Figure 18).