Life after Photoshop

5 ways to convert colour images to black and white

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Black and white conversion

With just a couple of exceptions, all digital cameras capture in colour, so if you want black and white images, you have two choices. You can use the camera’s monochrome mode, which will simply convert the image in-camera, or you can carry out the conversion on a computer.

This gives more control and better results, but there are several methods to choose from.

1. Convert to greyscale

Black and white conversion
Converting to greyscale is a quick and easy solution but doesn’t give any control over how colours convert to greyscale tones.

If you’re using a regular photo-editor like Photoshop or Elements this looks like the simplest route as it translates colours into shades of grey in a single step. However, you’ve got no control over how the software translates colours into shades of grey – a very important tool for creating tonal contrast in black and white. Second, this is a file format with a single greyscale channel, so you can’t then add colour toning effects, e.g. sepia toning.

2. Desaturate the image

Black and white conversion
Desaturating images is another quick solution but still doesn’t give you any tonal control.

You convert colour images to black and white without swapping to greyscale mode simply by reducing the image saturation to zero. That’s fine, except that this also offers no control over how colours are translated into shades of grey.

3. Channel/colour mixing

Black and white conversion
Channel/colour mixing lets you replicate the effect of traditional black and white filters.

The more sophisticated way to create monochromatic images is by adjusting the strength of each colour as it’s converted to a greyscale tone. By increasing or reducing the strength of each colour in the mix, you can make it come out darker or lighter in the black and white image.

You can only take this so far, though. Camera sensors use a mathematically interpolated ‘mosaic’ of red, green and blue photosites and by giving too much weight to specific colour ranges you soon start to exaggerate noise, edge effects and other digital processing artefacts.

4. Profiles and LUTs

Black and white conversion
Profiles and LUTs give you bespoke black and white ‘looks’. These are from Lutify.me, applied in Adobe Camera Raw.

These are a comparatively recent development. Essentially, they ’remap’ the original image’s colours on to new values and can come in both colour and black and white versions. Black and white profiles and LUTs convert colour values into shades of grey, just like the previous methods, but the ‘remapping’ as been carefully crafted for specific ‘looks’.

5. Gradient Maps

Black and white conversion
Gradient maps offer a degree of tonal control and the ability to apply toning effects.

This is a type of adjustment layer found in Photoshop and other programs which ‘maps’ a gradient you choose on to the brightness values in the picture. It’s not designed specifically for black and white but is very effective when you use a black-white gradient. You can even add a colour stop between the white and black end points to create toning effects.

Conversions are just the start

Black and white conversion
Using the right conversion process is a great start in black and white, but you’ll still need local adjustments and other tweaks (this is DxO Optics Pro 2) to make them really stand out.

Successful black and white imagery depends on more than choosing the right conversion method. Black and white images also benefit from skilled dodging and burning to intensify some areas and lighten others. Toning effects can add depth and atmosphere to a black and white image, and you can recreate the appearance of traditional film and darkroom processes with borders, textures and light effects.

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