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Converting a File to Monochrome

Ironically it is far better to convert a RGB file (ideally a Raw file) to black and white than it is to use the monochrome facility on your camera, as in this way you are retaining the full image quality. The simplest method for converting an RGB file to black and white is either to desaturate the image or to convert it to Grayscale. Neither of these produce satisfactory results; I would suggest that you opt for one of the following methods instead.

Start image 1. Often the most difficult task is identifying a file that will make a good monochrome. The strong tonal contrast, the obvious graphic qualities and a general lack of colour would suggest that this should translate well as a black-and-white image.

Method 1: Convert to Lab Color. An interesting, and quite a popular method that many Photoshop users prefer, is to use Lab Color; this should be available on most versions of Photoshop. Open the Channels palette for reference. To convert your file, go to Image > Mode > Lab Color. This has the effect of separating monochrome from colour, which should be visible in the Channels palette.

To remove the colour information, select the Lightness Channel, but then convert the image to Grayscale. This method offers advantages over simply converting the image to Grayscale as it retains good shadow detail and exceptionally smooth midtones.

Method 2: use the Black and White command. All Photoshop versions from CS3 onwards feature the Black and White command. To access it, make an Adjustment Layer and select Black and White. This dialog offers six sliders; Reds, Yellows, Greens, Cyans, Blues and Magentas; these allow you to fine-tune the tonal values of your converted black-and-white image. So, for example, if you want to lighten or darken a blue sky, use the Cyans and Blues sliders. The principle is very similar to Channel Mixer except that the Black and White command adjusts the actual colours in the image. Put simply, when using the Red slider in Channel Mixer, all the colours are adjusted to a greater or lesser degree. However, when using the red slider in the Black and White command, Photoshop is able to identify only those parts that are red and responds accordingly. This command also has a useful range of Default settings that you may wish to experiment with; they replicate the effects of a red, yellow, green or blue filter, which can prove particularly useful.

Finished image 1. The high contrast, coupled with the strong interplay of light and dark, help to make this a successful black-and-white image.

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If you randomly select and desaturate an image you might be disappointed; what works well in colour will not necessarily work as a monochrome. Use the camera’s monochrome option, and if you like what you see, retake the image in RGB, but convert the image in Photoshop. If you are shooting Raw, setting the camera to Black and White allows you to see the image in mono but still retain it in RGB.

Method 3: Use the Channel Mixer. If your version of Photoshop does not include the Black and White command, a good alternative is to use the Channel Mixer. This also retains the image in RGB.

Step 1. Go to Image > Adjustments > Channel Mixer. If your version has Channel Mixer as an Adjustment Layer, it is preferable to use that instead as the changes can be made non-destructively. Select the Monochrome box and the image will immediately default to black and white. By moving the three colour sliders, you are able to adjust the tonal values of each of the colour channels. Rather than move the sliders randomly, think carefully how each of the channels can alter the tonal values of the image. The blue slider, for example, will greatly alter the tonal values in a sky picture.

Step 2. It is important that the total percentage of all three channels adds up to 100%. Less than that and you compromise shadow detail; more than that and highlights can appear burnt out.

Step 3. To fine-tune this technique, try using Color Mixer in conjunction with Hue/Saturation. With your Background Layer active, make a second Adjustment Layer by selecting Hue/Saturation, so that the Hue/Saturation layer is below the Channel Mixer layer. By scrolling Master, the six colour channels will appear. Select each of the channels you wish to alter and use the Hue slider to tweak the respective tonal values. Do not expect to see huge differences, as this is an exercise in fine-tuning. Occasionally it also helps to use the Saturation slider as well, although excessive use of either of the sliders can cause parts of the image to posterize.

Start image 2. While this image clearly exhibits strong tones, the colour makes only a limited impact, and therefore should make an excellent image to be converted to black and white.

Method 4: Using the Raw Converter. If you shoot Raw (and the reasons for doing so are numerous), then you do have the option of converting your image in the Raw Converter. Once again the great advantage of using this method is that it is entirely non-destructive. Each Raw Converter is slightly different dependent on the make of camera, but look for the option that offers HSL/Grayscale. With this option open, you will be presented with eight colour sliders that allow you to fine-tune the tonal values with considerable precision. Make sure that the Convert to Grayscale box is ticked.

Method 5: using external software. Finally, an increasing number of monochrome enthusiasts are using software other than Photoshop to make their conversions, particularly Nik Software Silver Efex Pro (www.niksoftware.com). This software boasts unique algorithms offering an impressive tonal range. In addition to a very effective conversion facility, it has a number of interesting presets that allow you to mimic specific black-and-white films, although I sense you need to have been a darkroom enthusiast to truly appreciate the value of this.

Finished image 2. The contrast between the model’s flesh tones with her dark clothing and the dark background becomes much more apparent when this is presented as a black and white.

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Another solution is to go to the Saturation sliders and set all to zero, then move the Luminance slider until you achieve the effect you are after.