While some subjects look best in full, glorious colour, others can work better when rendered into black and white. Even though dedicated monochrome cameras exist, it’s easy to convert a colour image into monochrome and the end result can be as satisfying. Better still, you also have a colour original to return to.
This illustration shows how monochrome conversion can change the character of an image.
Cameras that allow you to capture raw and JPEG images simultaneously with the black and white mode enabled provide the best of both worlds: a quick monochrome shot and a colour raw file that can be converted later and will act as your archive file.
Greyscale conversion
The simplest way to turn colour originals into B&W is via Greyscale conversion. this is the process used when you select the monochrome mode in a digital camera. Unfortunately, you lose a lot of image data in the process.
Colour images combine three different colour channels: red, green and blue (TGB). Each channel can record 256 shades per colour, which when combined produces more than 16 million possible colour combinations (256 x 256 x 256).
In contrast, a greyscale image is made up of just 256 shades of grey, ranging from pure black to pure white. to obtain a greyscale image, all the colour information is discarded and the brightness data in the three channels is combined into a single channel that records black, white and intermediate grey tones.
The Greyscale conversion tool is usually found in the Image>Mode sub-menu.
An important factor to bear in mind when using this conversion method is that there is no way to restore colours if you don’t like the result you’ve obtained. Consequently, this method should only be used on copies of original image files.
Another conversion method ““ which doesn’t discard colour information and is just as quick ““ is to move the saturation slider all the way to the left. If you don’t like the end result, moving the saturation slider back to the centre of its range will restore normal colours.
Moving the saturation slider all the way to the left suppresses colours in the image.
Both these methods are relatively crude. Sometimes they’re successful; at other times not and they provide little or no control over how the primary colours combine to balance the brightness”¨and contrast differences between the image tones.
Channel mixing
Greater control over the reproduction of image tones is provided by separately adjusting each of the three colour channels ““ red, green and blue ““ that make up the image. Sophisticated editors provide B&W conversion modes with sliders for adjusting individual colour channels and fine-tuning the balance”¨of the image tones. Some also include pre-sets that make it easy to replicate popular effects.
Selecting the Black & White mode in Photoshop.
The Black & White mode in Photoshop includes sliders for adjusting the red, green and blue colour channels as well as sliders for complementary yellow, magenta and cyan adjustments. Hue and saturation sliders allow the intensity of colours to be adjusted, while a dropdown Preset menu contains presets for various filters.
Working with an adjustment layer
The Layers dropdown menu in Photoshop contains a black and white adjustment layer, which is accessed by clicking on Layer>New Adjustment Layer>Black & White. This opens a palette panel that contains similar sliders to the Black & White conversion mode.
Selecting the Black & White adjustment layer in Photoshop opens a palette with colour adjustment sliders and a dropdown menu of presets.
As in the Black & White mode,Ӭ sliding a control to the left darkens the nominated colour while sliding to the right brightens it. The preset adjustments from the drop-down box mimic the effect of traditional coloured filters with black and white film and can provide a good starting point for further adjustments.
Toning
When black and white conversion doesn’t quite deliver the end result you want”¨you may wish to try toning. The most common examples of toning are sepia, which can be anything from yellow to deep brown; and blue, which can vary between cyan and violet. However, there’s nothing to stop you from experimenting with other tones if they suit your image.
oning adds emotional value to monochrome photos. Warm sepia tones usually create a nostalgic impression. They can be flattering for portraits of people as well as other subjects like landscapes and architectural shots. Blue tones convey a cold, desolate feel and are ideal for subjects like winter landscapes.
Toning should generally be subtle; not strong or garish. It’s best to start with”¨a photo you’ve already converted to black and white using a non-destructive method that keeps it in the RGB mode.
Checking the Tint box (circled in red) lets you adjust the Hue slider to select the colour for the toned image. The Saturation slider controls the intensity of the colour in the tone.
The Curves tool can be usedӬas an adjustment layer to tone B&W images by making adjustments within the individual colour channels.
Select Layer > New Adjustment Layer > Curves and click on OK to create a new layer and bring up the Curves palette.
To create this rather strongly cyan toned result we selected the red channel in the Curves palette, clicked on the central point on the diagonal and moved it slightly down and to the right. (Moving it to the left would have produced a red tone).
You can also apply different tonesӬ to highlights and shadows in a single image using a technique known as split toning. Split toning works best with high-contrast images.
Select Layer > New Adjustment Layer > Colour Balance and click on ‘OK’ to open the colour balance dialog box.”¨Set the Tone Balance to Shadows and move the Cyan/Red slider to -30 and the Yellow/Blue slider to +30. Then set the ‘Tone Balance’ to Highlights and move the Cyan/Red slider to +40 and the Yellow/Blue slider to -30.
This illustration shows the original B&W image in the lower left corner, with the shadows and Highlights Tone Balance above it. The split toning end result is in the lower right corner.
Photoshop and Lightroom make it easy to use split toning to produce duotones (with two colours), tritones (three colours) and quadtones (four colours). You can achieve similar results with almost any editor that supports Layers, although it’s less straightforward and requires a fair amount of experimentation. Regardless of the method used, only 8-bit greyscale images (JPEGs) can be converted to duotones.
The Duotone dialog box is opened by selecting Image > Mode > Duotone, which provides a dialog box with presets, a selection box for choosing the type of duotone and four boxes for selecting colours. Make sure the Preview box is checked to obtain a live preview of changes as they are made.
The Type box lets you choose between Monotone, Duotone, Tritone, or Quadtone, while clicking on each colour box opens the colour picker, which allows you to select a colour. Adjusting the position of the colour picker enables you to change the lightness and intensity of the selected hue.
The best results are obtained by starting with the darkest tone first (hence the default black selection in the top box). Then work progressively down, leaving the lightest colour for the lowest box. Further adjustments can be made by clicking in the curve box next to the colour ink box. this opens a Curves dialog box that lets you adjust the duotone curve for the selected colour.
Creating a tritone image in Photoshop, using the colour options and Curve adjustments dialog boxes. The end result is shown below the screen grab.
Experiment with the settings so that the tones suit your photo and click on OK when you’re happy with the end result.
Shoot with monochrome in mind
When taking photographs for conversion into B&W, focus on differences between tones in the subject and look for shapes and patterns that can be enhanced by discarding the colours in the scene. If you start with the image in colour, it’s easy to manipulate brightness and contrast with separate adjustments to the colour channels in the image when converting it into monochrome.
The results are similar to those obtained with colour filters with B&W film. To darken a particular colour, use a filter colour that is complementary to that colour; to lighten a colour use the same coloured filter.
This set of images shows the effects created by different colour filters. Clockwise from top left: yellow filter, red filter, green filter, blue filter, infrared filter, original colour image.
Useful links
www.bit.ly/convert-to-monochrome
www.bit.ly/convert-to-grayscale
Excerpt from Photo Editing Pocket Guide
