Black and White Photography (Part 1)

Back in the 80s, Black and White was often seen as old fashioned and uninteresting. Most developing labs could not even deal with black and white film, and had to send it away to be developed. It became the domain of those with their own darkrooms (ahhhh the good old days).

Since the digital revolution black and white has started to boom again. Black and white is a bit of a misnomer, as an image consists not just of black and white pixels, but many shades of grey in between. But who am I to go against the well established convention so I'll stick to calling it black and white (B&W for short) or monotone.

By removing colour from an image, it focuses the viewer’s attention on form and composition, and helps emphasise qualities in the image such as shape and texture. Although most cameras have a mode to shoot in black and white, it is always better to shoot in colour and convert to monochrome later. You will have more control over the conversion process, and you'll retain the option to keep the colour version as your preferred option.

The skills needed to take good black and white photos are quite different from colour, as it is often the colour that attracts your eye to a particular picture, whereas with black and white, all you have are different levels of brightness. The skill that needs to be learned is to see the world in black and white.

Converting to Black and White

There are many options available to you to convert your colour image into monochrome image. These include:

• Greyscale
• Desaturate the image
• The Channel Mixer
• Use LAB mode
• Luminosity Blending

There may be others depending on what software you use. I (Scott) haven’t had a lot of experience with LAB mode and Luminosity Blending.

Convert to Greyscale
This is the simplest way to create a black and white image from a colour photograph, it also probably produces the closest image to what the camera would have come up with if you used the black and white mode. It is often dismissed as not worth bothering with, because it is so simple. However I think that if you just starting to try monotone photography you should give it a go - you can always hit undo if you don’t like the results.

Note: This option may automatically reduce the image down to a single channel. Many image editing filters and effects require a 3 channel image to work, so you may then need to convert the image back to RGB mode (although it will remain grey as the colours have been removed).

Desaturate
Another simple method that will produce quite a different monotone image from that of the “Convert to Grayscale” option. Sometimes it can look better. It does have the advantage that it leaves the image as an RGB image, and therefore you can apply all the usual effects and filters.

The Channel Mixer
The channel mixer is probably one of the most used conversion methods. The chip in your camera is a colour device, with three primary colours that come from the sensor. A black and white image contains just one channel of information, there must be some element of “weighting” involved (i.e. how much of the red, the green and the blue should be used to make up the shade of grey).

Back at the dawn of photography when black and white was the only option, photographers used coloured filters (in front of the lens) to either increase or reduce the a particular colour (a red filter on a blue cloudy sky would exaggerate the contrast in this area in the black and white image). All that is happening is that the red filter is allowing red light through and blocking other colours. Colours that get blocked appear darker ; in this case blue is getting blocked, being at almost the total opposite of the spectrum to red and therefore very dark. This way you have more control over the conversion process, as the channel mixer acts a little like these filters.

Depending on your software you will see at least three sliders labelled red, green and blue. There will probably be a check box labelled monochrome which needs to be selected if you want the output to be a greyscale image. The values of the colours should add up to 100% if you want the resulting image to have the same average brightness as the original.

Setting the red value to 100% and green and blue values to 0% will show a bright area corresponding to the areas of red in the image. If you want to mimic the luminosity received by the human eye, you should set the values to about 30% (red), 59% (green) and 11% (blue)

Hue-Saturation Adjustment Layer
This is a very flexible way of converting your image to black and is it keeps the original colour image (on the background layer) in tact while allowing you to work with the black and white image. But requires a more in depth knowledge of the software you are working with. The effect can be very similar to the Desaturate option above, but using a Hue-Saturation Adjustment Layer offers you a similar level of control to the channel mixer. In fact, if you use two Hue-Saturation adjustment layers, you will have even more control.
Try this...

1. Create two hue-saturation adjustment layers.
2. On the uppermost one, set the blending mode to 'colour' and the saturation to -100.
3. You can now adjust the hue slider on the lower one to select the colour filter you want to emulate, and the saturation slider in this layer to control the amount of effect the filter has.

It is worth having a playing around with and see what effects you can get.

Use LAB mode
LAB mode is just one of many colour spaces that available in Photoshop (and other packages). LAB mode is able to represent the largest range of colours possible in an image. Like RGB, it is a 3-channel colour mode. However, whereas RGB mode uses the amount of each of three primary colours, LAB uses a lightness channel and two colour channels. Therefore if you convert your image to LAB mode, and then click on the Lightness channel in the Channels Palette, you will see the black and white image. To delete the 2 colour channels now, simply change the mode to greyscale and the colour information is removed from the image. Although LAB colour is based on the human perception of colour, black and white images created in this way often appear too light to too dark. There is a technique called luminosity blending which can correct for this.

Luminosity Blending
This is one of the more complex methods of converting a colour image to black and white. It involves putting the photograph onto a layer above a plain white layer, and then changing the blend mode from 'Normal' to 'Luminosity' (called Luminance in Paint Shop Pro).
Here's a step by step approach for Photoshop users:

1. Promote the background layer with your photo on to a normal layer by renaming it or double-clicking on the word 'Background' in the layers palette.
2. Insert a pure white layer beneath the picture layer (any colour other than white, grey or black will add a tint to the picture)
3. Set the blend mode of the picture layer to Luminosity.