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Black & White Inkjet Printing Comes of Age

In a print article on pages 14-15 of the Year End 2005 issue of the ASMP Bulletin, fine artist and master of inkjet printing John Paul Caponigro, explains why black-and-white inkjet printing has finally come of age. In the companion piece featured here Caponigro presents a tutorial on digitally converting a color file to black-and-white for optimal tonal control.

Converting color to black and white - part I

Using digital methods to convert color to black and white will give you unparalleled control over the tonal structure of images.

All RGB images are composed of three black and white channels. If an image is neutral, the three channels will be identical. Similarly, if an image contains subdued color there will be little variation between channels. In contrast, if an image contains a significant variety of hue and saturation there will be dramatic differences in the tonal structure of an image. You can use the differences in the tonal structure of the separate channels to control conversions from color to black and white by mixing the channels.

Among the many ways of converting color to black and white by mixing channels, two methods stand out above the rest: using the Channel Mixer and turning channels into layers. Using the channel mixer is the simpler of the two methods.

Simply create a Channel Mixer adjustment layer and check Monochrome. (You cannot mix Grayscale images as they contain only one channel.)

The default settings are 100 percent of the Red channel. You can use any percentage of the three channels. There is no ideal mix of channels. Every image is different, and there's plenty of room for interpretation. Given the same image two different people might convert the same image differently.

When choosing what percentage of the three channels to use, it helps to see the separate channels side-by-side. In order to do so, simply duplicate the file to be converted and select Split Channels from the submenu in the Channels palette. (An image must be flattened in order to access this feature.) This will break the channels of an RGB document into separate Grayscale documents. Arranging these documents side-by-side will enable you to see the differences between the channels and help you select your preferred mix of channels when you return to the original RGB document.

An important guideline to use when mixing channels is to make the combined total percentage of the three channels 100 percent. Higher percentages may clip highlights and/or reduce the density of blacks. Lower percentages may clip shadows and/or reduce the brightness of whites. If you do choose to use a combined percentage higher or lower than 100 percent, use the Histogram palette as a guide to avoid clipping.

When making a conversion, err on the side of reduced contrast to avoid clipping. Don’t try to establish optimum contrast in the midtones during the conversion. This is best done after conversion using Curves. Instead, during the conversion, focus on establishing the fundamental light and dark relationships an image will contain after conversion.

Avoid the Constant slider. Using it will reduce the dynamic range of your image and may clip values in an image.

Changing the colors in an image will change the results of a black and white conversion. After you've used the Channel Mixer, try using a Hue/Saturation adjustment layer (placed below the Channel Mixer adjustment layer or before the black and white conversion) to change the hue and/or saturation contained in an image. In addition to changing all colors in an image (Master) you can also target single ranges of color (Red, Yellow, Green, Cyan, Blue, Magenta) from the pull down menu in the Hue/Saturation dialog box. With this addition, you can refine the tonal structure of an image even further. When making very  Pronounced color corrections with Hue/Saturation, be careful to avoid introducing posterization.

You can also make different black and white conversions to different areas of an image if you select them before using the Channel Mixer. Simply select one area, then make a conversion for that area using a Channel Mixer adjustment layer. Then select the rest of the image and make a different conversion using another Channel Mixer adjustment layer. You can do this for as many areas as you like; each will require a separate selection and a separate Channel Mixer adjustment layer.

Once you have converted an image to black and white you can refine (lighten, darken, add or subtract contrast) the new tonal structure of an image globally using Curves or locally using a layer set to Soft Light for dodging and burning.

You'll find the power and precision of this method so compelling that you will change not only your image enhancement methods, you will also begin to see new possibilities when making exposures. In addition to seeing the luminosity structure of an image, you will also see that its structure is variable when significant hue and saturation are present. Simply put, a saturated hue can be either light or dark. And, with these techniques, you can make these possibilities work for you.

Author of Adobe Photoshop Master Class John Paul Caponigro is an internationally respected fine artist and a passionate lecturer and workshop instructor whose clients include Adobe, Apple, Canon and Epson. Find part II of this article at adobe.com. Visit johnpaulcaponigro.com for more information. Sign up for free e-news by e-mailing subscribe@johnpaulcaponigro.com.

Captions:

A full color RGB image.

The Red channel.

The Green channel.

The Blue channel.

The full color RGB image converted to black and white.

The layer stack for the final black and white image.