So most of us have a DSLR camera that captures images in colour but how do achieve the best Black and white photo conversion. What works best to capture the perfect black and white photograph - filters, the camera B & W mode or photo editing software. Professional photographer Karl Taylor reveals all!

To understand black & white photography you first need to understand a little bit about colour. As you are probably already aware, the primary colours of light are red, green and blue. In equal mixture, primary colours form white light. Secondary colours are cyan, magenta and yellow. These are opposite to the primary colours and each theoretically cancel out their opposite colour.

Recording in black & white provides a representation of a given colour, but instead of the colour being visible in the image, only the brightness or tonal value of the colour remains as a shade of grey or black or white. The range of tones that can be achieved in a black & white image is anything from black through various increasing tones of grey right up to pure white. The maximum purity of the white achievable depends on the base white of the paper that you are printing on.

Part of the art of black and white photography is to understand how the tonal value of colours in a scene will reproduce as a shade of grey or if they will appear as black or white. You may expect each colour to record as a different shade but some colours will reproduce as very similar shades even though the colours look completely different to the eye. Filters placed in front of a camera lens either enhance or reduce the coloured light passing through it and can further affect reproduction. Additionally the material you are recording the image onto and printing onto can also influence the final black & white image.

When using film, professional photographers are aware that each type of black and white film gives a different response to certain colours. Most reproduce a slightly different version of black and white and photographers have their personal favourites. More serious black and white photographers would also place colour filters in front of the lens to increase the contrast and change the tonal range of their image. The common colour filters applied for black & white film photography are deep red, an orange, a green or a yellow filter. But let's face it, film is going the way of the Dodo and the computer has replaced the darkroom, so what are our options?

In today's digital age we are now capturing images using sensors that only record in colour, if we want black and white we convert the image on a computer later. The level of success with this method largely depends on the conversion techniques you apply and your understanding of the colours in the scene. There are a variety of techniques that you can apply and each can yield a different result. It is worth noting however that although we are shooting on colour cameras it is still possible to influence the effect of the final black and white conversion at the capture stage by using filters.

Admittedly, having tested the technique of different colour filters on RGB capture, I would say the results vary in degree of success and in most cases with the right knowledge you can adjust an RGB colour image very precisely using good black and white conversion methods in your software. However I have had interesting results using a green filter on a colour digital camera and would also highly recommend using a polarising filter for most of your black and white landscape photography. Polarising filters increase the richness of colour and contrast in your image, which in turn means that your software has richer colour information to play with when making a black & white conversion.

But lets learn a bit about colour first.

Each opposite colour would cancel the other out - for example Red is the opposite colour of Cyan and Blue is the opposite colour of Yellow. Combining two of the primary colours forms the secondary colours. For example combining Red and Green light would create yellow. Combining Blue and Green light would create Cyan and combining Blue and Red would create Magenta. If you were to combine opposite colours you would create Black. If you combined all 3 primary colours you would create white light. If you combined all 3 secondary colours with subtractive mixing using optical filters you would create black.

As an experiment of black & white conversions, I photographed a series of test images using an RGB colour digital camera (with a CMOS sensor) but I also shot the scene with colour filters applied. The filters I used were the traditional colour filters used for black and white film and not designed for RGB capture, but I decided it would be an interesting exercise regardless.

1. A straight colour image with no filter

2. A straight colour image, with a Polarising filter

3. An Orange filter attached to the front of the lens

4. A Red filter

5. A Green filter

6. A Blue filter.

Each image was then loaded into Photoshop and converted to greyscale mode (the most simplistic method of creating a black & white image). I then decided to convert the original colour image (with no filters) using the black and white adjustment layer (a more versatile method of conversion) but this time manually adjusting the tonal range using the Photoshop colour sliders in the black and white conversion palette. In each case I was able to eventually achieve a very similar result to the standard greyscale conversions taken with the colour filters, therefore proving that using colour filters during RGB capture is rather futile.

It was, however, more difficult to achieve as good a result as the image taken using the polarising filter and I would also add that a straight black & white conversion from an RGB image with the green filter applied gave a more appealing starting point in this test. Further experimentation on different scenes at different times of day would be required to reveal any overall benefit.

Some digital SLRs have a monochrome mode where you can preview the image on the LCD screen in black & white. This capture mode is not a true black and white capture only a conversion preview of the colour file, but still useful for checking results when trying different filters for black and white.

In practical terms most of us will be shooting normal colour files in order to capture a good colour image and then wanting to make the best conversion possible. So let's take a look at some of the techniques you could use in Photoshop CS4 to make good black and white conversions from a standard colour image.

The first and most obvious is to use a black and white adjustment layer, this will provide you a colour palette whereby you can adjust the brightness value of a given colour in your scene and reproduce it as a different shade of grey. By using the colour selector slider you can physically place your mouse on your image and slide it to see the effect on a given colour. When using this technique I like to make a separate copy of the colour image and keep it open on my desktop in another window as a reference to where certain colours are in the scene. By using an adjustment layer instead of an actual action you can flick the layer on and off to check your results.

Often you will find as you adjust your image colour values certain parts of the picture look better in black and white at one setting while other parts look better at another setting. If this is the case I create a new black and white layer for each of my favourite parts of the image and name the layer accordingly then rub through the layers afterwards to reveal the best part of each one.

The Channel Mixer adjustment layer can also be used for creating black and white images by checking the monochrome box and mixing the channels at various percentages to yield different results. In the tab at the top of the palette is a useful drop down menu that applies a similar effect to using the colour filters on black and white film that I mentioned earlier. Again creating new layers with different percentages and then blending the required areas can achieve more personalised results.

Another interesting technique that I learnt from a fellow photographer is to apply two Hue and Saturation layers to your image, set the top layer to the layer blend mode colour and set the saturation to "-100". On the bottom layer you can then adjust the hue slider to recreate the effect of a multitude of colour filters in conjunction with the saturation slider. Again saving new flattened layers from your favourite results and blending them later.

With the new Camera Raw palette in CS4 (accessed through Bridge) you will find a greyscale conversion tab that offers a very versatile control panel with an additional tab for creating split tone images (sepia effects etc.) On the greyscale conversion palette there are more colour sliders than the black & white adjustment option in Photoshop (don't ask me why?) these extra sliders give you slightly more versatility in your conversion but you are unable to work on layered files and are restricted to working with a flattened tiff, jpeg or RAW file.

Other tips you might find useful with practise are to create a gradient map on top of your black and white conversion allowing you to map a specific tonal range over the whole image by pre-selecting which tone you want to go where - this can be useful for adding a boost of contrast to parts of your image by history brushing away areas you don't require or if you applied this is an adjustment layer you could apply a mask to select the areas you wish to retain and remove.

To fully understand this process I advise you read about layer masks and gradient mapping in Photoshop and related manuals.

For a final contrast boost to your black and white conversions I find the Unsharp Mask filter at a setting of about 20/50 (for a 22MegaPixel Image) very effective, then use the edit > fade slider to adjust the image to suit. A setting of 15 percent and 20 pixels would be more appropriate on a 12MP camera.

Finally and most importantly don't forget that all of the above is totally irrelevant if the image you have captured doesn't work. I don't believe a bad colour image will be miraculously saved by converting it to black and white! Black and white photography is still photography and capturing a creative image is still key.