Black & White Digital Photography

(Monochrome)

Black & White photography is about capturing images with an absence of colour, for it relies solely on the variation in tonal range present in an image to distinguish objects from one another. In essence, the use of monochrome images allows a simplicity of purpose to be portrayed in a graphical way, and enables powerful images to be created. The absence of colour with which to analyze and grade what we see forces us to look in more detail at what is depicted. It makes us think more about what we are viewing which our brains normally carry out in an automatic way according to what we perceive to be normal and correct. It is the original way photography evolved, using film with a single layer of emulsion, and is often referred to as monochrome. Colour photography, using three layers of emulsion, is by comparison a much more recent development, although it is now considered the normal way of producing photographs as it replicates scenes and objects as our eyes see them, in colour.

Today in digital imaging, and particularly in association with software image editing programs, the term greyscale is used since the tonal values of B&W are aligned along a grey tonal scale from black to white. Here is a greyscale wedge generated in Photoshop. It consists of 41 steps and each step is the equivalent to a 1/3rd Ev exposure step difference between pure black and pure white. The popular Jpeg file format is an 8bit file format which means that 256 tonal steps ( 2^8 = 256) can be used to depict the tonal range in an image from black to white. So just over six different tonal levels are available to depict the range in each 1/3rd Ev step.

41 step wedge tonal greyscale - 1/3rd Ev steps

As it relies on the tonal values in the scene to be captured, the contrast between the tones becomes important. Low contrast images with a great many tonal levels can be used to depict high levels of detail. High contrast images, and the highest is where there is just two tones, pure black and pure white - (often referred to as line photography or line drawing as this can also be accomplished by hand - e.g. pen and ink drawings) - give a starkness of comprehension that is compelling to the observer.

How many of these tonal steps can be captured in any particular image varies depending on the lighting conditions prevailing at the time of taking the shot in just the same way as it does with colour images and is referred to as the dynamic range. Please see  Image Exposure  and  Dynamic Range Assessment  In low contrast lighting most tones will be observed. In high contrast scenes i.e. when it is very bright, tones at either one end of the scale or the other, or sometimes both, can be lost. This has resulted in the development of the well known techniques of burning and dodging. Bringing lost tonal values, captured by the film negative but not reflected in a 'straight' print (one of a fixed exposure value), into the viewable tonal range by varying the exposure over the print. In other words giving some areas more or less exposure than others. This is not just the preserve of B&W of course, the same techniques can and are just as easily used with colour print images, but are perhaps more historically associated with B&W. Although not as widespread in it's use as in film capture times, as a wider range of image manipulation options are available to the digital image worker, nevertheless these techniques are still practiced.

Working in Black & White

B&W has often been undertaken by amateur photographers with home darkrooms in film photography times because of the comparative ease and low cost with which developing and printing could be accomplished. Colour developing and printing, whilst also undertaken at home by many, especially before the advent of digital imaging, is nonetheless a much more complicated and expensive business. There's many a schoolboy whose first experience of B&W photographic developing and printing was undertaken in the smallest dark space available, the cupboard under the stairs.

Although with the advent of colour photography B&W fell by the wayside for some years, especially when the cost of colour fell as it became more popular, in more recent times it has re-emerged as the medium of choice by those looking for a more graphic image reproduction since it relies on tone and not colour. And this is especially true of the present day advertising trends. However the reality for users of film is that even if you develop and print B&W yourself at home, the costs have reversed and are higher than that for colour, since the demand is now small by comparison. All present day consumer Developing and Printing - D&P - using mini-labs is geared up, as you might expect, to colour reproduction. Only the more specialist labs now undertake Black & White, at a cost.

Today, with the advent of digital photography, inkjet printers, and the computer manipulation and management of digital images, much has changed. Working in colour is now standard, the accepted norm, especially since it is, in comparison to colour film photography, so easy to do. But B&W is still popular, and rightly so, and whilst there are those that mourn the passing of the days of the B&W darkroom work undertaken by the masses in favour of digital means, the truth is that working in B&W has now gained another new lease of life because it can be no more costly to work in B&W using digital imaging than in colour. And a compelling reason why so many have switched. Cost and ease of use.

Taking Black & White images

Unlike that of using a film camera, where if you wanted to shoot in monochrome you used B&W film, with the advent of digital there are three ways of producing monochrome shots using a digital camera. The first is to take it as a monochrome image. The second is to take it as a colour image and convert it in-camera to monochrome. And the third is to take it as a colour image and convert it to monochrome afterwards in an image editing program. Each method has both advantages and disadvantages, and we'll discuss and detail what they are, but perhaps more importantly the method you chose to use might well revolve around the digital camera you have. For many digital cameras only produce colour image files, there is no monochrome mode or in-camera digital filter conversion. These are options that have generally arrived in more recent years with the newer digital cameras as makers discover the desires of digital camera buyers to shoot in monochrome with the renewed popularity of B&W photography. 

However before we look at all the options available and the best methods to use, it might be best first to take a brief look at a subject that has a relevance to monochrome tonal image quality, the use of lens filters.

Using coloured filters in monochrome shots

It might be strange to some that B&W photography can involve the use of coloured filters, but the fact is it does, if you choose to do it. Taking a monochrome shot through a coloured filter alters the tonal values in a way that chemical darkroom work cannot replicate. It changes the relationship the tonal values each colour produces has to others in the scene depending on the colour of the filter used. The main filter colours employed are, Yellow, Green, Blue, Red, and Orange.

• Yellow ; absorbs UV & blue:  Most Yellow B&W filters are weak in strength and don't absorb all the blue. They are essential to give any contrast between clouds and sky. They tend to darken a blue sky, accentuate clouds, and they also lighten foliage.

• Green ; absorbs UV & blue & red:  This lightens foliage and slightly darkens sky to a stronger level than yellow. It also makes red objects and skin tones darker. So it's ideal for predominantly green landscapes and adds a healthy tanned look to outdoor portraits. 

• Yellow-Green ; absorbs UV & blue & red. Theoretically perfect rendition of landscapes, correcting foliage and sky. Useful when people are also visible in the image.

• Blue ; absorbs yellow, green & red:  This lightens blue subjects and increases haze in landscapes. But it is good indoors for portraits taken under tungsten lights.

• Red ; absorbs UV & blue & green:  It darkens blue skies and water, increases contrast, deepens shadows, cuts haze, and lightens red objects. It's the filter with the strongest effect. It exaggerates cloudscapes and dark blue skies can become virtually black. is excellent for cutting haze in distant shots and good for rendering detail in brickwork. Anything green however comes out very dark. 

• Orange ; This has mainly the same effects as red, but to a lesser degree. It tends to absorb more blue than green, so is recommended for UK skies. Cuts through haze and increases contrast. Subdues freckles on faces, but can render foliage too dark. 

As you can see each colour has particular effects, some of which mean that careful use must be made of each type.

Generally the most used filters are Yellow, Green, Orange and Red. Blue is rarely used, and only for specific shots. We have a combination Yellow/Green filter, an Orange, and a Red. 

** We must point out that many digital cameras have integral software filters ( Red, Blue, Green, Yellow, Orange) that can be used when taking a shot in monochrome mode. These are just as good as using 'real' filters, better in many ways as no light loss occurs as no filter factor is involved. (see next chapter)

**** The use of coloured filters with monochrome shots can only be undertaken if the camera involved has a monochrome capture mode. If it hasn't you can't use them. All that will result is an image with a weird colour cast.

Using other filters

There are three other filters that can be used with Black & White digital photography, and in many cases they are not thought of or normally considered because they are not associated with monochrome. These are the Polarizer, The Neutral Density - ND - and the Grey Graduated.

The Polarizing filter is not concerned with colour, but rather the angle of the rays of light entering a lens. So it's useful for removing reflections off shiny subjects and increasing saturation. It' also used to remove the light reflection from skies and gives increased contrast making skies look bluer and clouds stand out. The ND is used to increase general exposure values for longer shutter speeds and again this is not about colour but tonal values. The Graduated filter, the neutral grey grad type, are again not concerned with colour, but rather to balance exposure and tonal values. The main use of a grey grad is to even out large differences in exposure values, say when there is a very bright sky in comparison to the ground. A grey grad can be used to filter out some of the light from the sky, allowing the ground tonal values to register whilst still keeping tonal detail in the sky.

An important point to note here is that virtually any lens filter used on a camera has an effect on the levels of light entering the lens. They stop a certain amount of light. This is called their filter factor. Please refer to our page on  Filters  for more details about all types of lens filters. And those most useful for use with digital cameras.

Producing Black & White Digital shots.

The Monochrome shot.

Being able to take an image in monochrome using a digital camera has the advantage that at the taking stage you can see the result on the LCD screen. If your camera allows you to do this it's an option you can consider. Another advantage is that you have the option to use the coloured filters that have for so long been used in monochrome work to change the tonal values of a recorded image. The immediacy means that you can soon see if the image 'works' in monochrome rather than colour, if the use of a filter of one colour or another makes a difference, and by how much. Some cameras have monochrome modes that allow the shot to be taken as if a coloured filter had been used on the front of the lens. This has some real advantages if you want to do this because no actual filters are involved. There is no additional cost involved, there's no filters to buy, so it doesn't matter what the filter size is on the front of the lens used. And there is no increase in exposure needed.

The downside is that once you have taken it, you can't alter it much. You can take different versions of course, with and without filters, but if you are taking a scene that involves movement of any kind then you are rather restricted, in just the same way that you would be if you had used a film camera loaded with B&W film. Although you still have an advantage, a big one, in that you can review what you have taken and delete and re-take them if you need to and are able to do so, the subject matter being either fixed or stationary.

One other advantage of shooting in monochrome is that image files take up less space on a memory card than colour shots. This is because there is only tonal information. Colour images contain both colour and tonal information.

The colour shot converted in-camera.

There are many digital cameras that don't have a monochrome mode, most DSLR's don't. Others don't have a dedicated shooting mode but allow the user to 'convert' the image to monochrome in the camera after taking the shot. With certain cameras that work like this you can also mimic the use of coloured filters in the conversion from colour to monochrome. It's usually the case that when conversion takes place in-camera the original file is left untouched and another file is generated for the monochrome version. 

In a sense this is okay. The colour original is safe and can be used as such, or converted again later. But it reduces the available space on a memory card for no good reason. Another downside is that when you do convert like this you are relying on the processing in the camera and the image on the rear screen to produce a decent monochrome shot, just as you do if you take it in monochrome in the first place. If you have to take the image in colour then you might just as well leave it like that and convert it later in an image editor.

The colour shot converted later.

If you have a camera that only takes colour shots then you have no choice but to shoot in colour and convert later. But this is not as restrictive as you might at first think. Indeed whatever type of camera you have, and whether it has a monochrome mode or not this is actually the best all round option. The shot is in colour. You can try converting it to monochrome and if it doesn't work you have lost nothing. And because you are using digital imaging you have the option, with some image editors, of replicating the effects of using any coloured filter. So the choices you have are in reality much wider than with any other option.

Using filters

Whatever mode you shoot in, colour or monochrome, please note that the UV, Polarizer, ND, and Grey Grad types should be used at the image taking stage. The mode used, colour or monochrome, is immaterial to the effect they have, which cannot be replicated afterwards. You can generate a graduated filter in image editing software, and it will do exactly what the real filter does. But this only works with what tonal values exist in the image file being altered. If sky detail has not been captured for example, this won't restore it. And there is no way of replicating the effects of a polarizing filter, UV or ND digitally at all.

Converting colour images to monochrome in image editing software

There are a number of ways of converting colour images to monochrome, and some work better than others. We'll go through all the options that are available in turn. One problem you may encounter is that the image editing software program you use may not have the tools and options that allow you to choose which way to convert an image to monochrome. We will deal with that, and what you can do in certain programs to overcome this.

The Greyscale mode

Virtually all the image editors we have ever come across seem to offer this option, even simple image album software that just has very basic tools such as crop, rotate, lighten, darken, red eye removal etc. It's a quick and easy one click solution. The only problem is that once done there are limited adjustments to the image you can make. This is because it removes all the colour information, the three colour channels, RGB, and replaces them with just one tonal channel from the information they contain. Not all the information from all the channels is used. Usually the most is derived from the Green, anywhere between 60-70%.The Red contributes 25-30%, and the remainder, about 5-8% on average, from the Blue. There is no hard and fast rule, the mixture used is just what those compiling the software thinks looks right in their opinion.

Once converted in this way the changes that can be made are contrast and brightness values, individually or in the levels or curves tools. And altering the tonal values using dodging and burning. For some this is enough, and to be honest there is quite a bit you can do, but it is limited to subtle changes. If you have taken a monochrome shot in the first place, with or without the use of filters, then this is all you can do anyway.

The Hue/Saturation mode

This is similar to, but not the same as, using the plain Greyscale mode. Here you open the image and just de-saturate it, using the hue/saturation command tool, pulling the saturation slider to zero, 0. This has the effect of removing the colour from all channels, and produces, normally, a darker image with more noise, because most noise comes from the red and blue channels. This is not seen at small image sizes but becomes apparent at larger one's. And is particularly noticeable if any large red or blue areas are present. Which is why, as a rule, most information is taken from the green channel for monochrome image reproduction.

Our view is that in many ways, this produces worse results than the plain greyscale conversion, because of the noise from the red/blue channels, although there are those who prefer it. It is simply a matter of choice.

The Channel mixer mode

If your image editor has this option then it is without doubt the best way of producing a monochrome image. Basically this is a variable greyscale mode, where you the user decide what amounts of information from each channel is used. When this is used all three channels, RGB, are available, and the percentage taken from each can be altered to suit, with endless permutations thus possible. You can just use the green channel, the red channel, or the blue channel, or whatever mix you like. One channel, two channels, or all three, and the percentage of each used. 

Because of this it is possible to replicate all the effects that using colour filters when taking B&W shots produces. The only problem is that it takes longer, which is not really of concern if it produces the monochrome image you want, and is only available with certain image editing programs. The full Photoshop has a channel mixer, but Elements and many similar programs that digital camera users prefer don't. Even quite advanced one's such as the latest version of ULead's PhotoImpact we have tried don't have this option. Yet it has advanced options for dealing with HDR images, so you can never tell by their cost or complexity whether programs have a channel mixer or not.

If you are in this position there are a couple of options. One is to download and try the free open source image editing program, The Gimp. This can be found at  www.gimp.org  It has a channel mixer and several other interesting options of use with colour to monochrome conversion, Decompose being one. 

Another is to use Google's free Picasa 2 image organizing and basic editing program, as this has several Black&White modes, and supports variable colour channel mixing. 

Alternatively, if you have a program like Photoshop Elements that has no channel mixer mode, but does have an option to work with layers, then there is another way.  Channel mixing using layers.

Channel Mixing using layers

This is a way of converting colour images to monochrome we have developed that can be used with an image editor that does not have a channel mixer mode. We have not to date seen this described elsewhere. This seems strange considering the number of books that have been written on digital imaging over the last few years, and particularly those not only on Photoshop CS2 and earlier variants, but Elements too. Perhaps it is because Photoshop has the channel mixer. Elements users are just encouraged to move up if they want the advantage. Unless of course someone has also found this technique, but has either not publicized it, or we have just not read about it. 

Anyway we will describe what you need to do. It's not over-complicated once you get the hang of it, but does require undertaking in a methodical manner. So it's not particularly quick. But you get there in the end. And the flexibility you get makes it in our opinion worth the effort. So if you would like to give it a try, read on.

These are the commands to use in Photoshop Elements. For any other image editor you will have to adapt as you see fit. But we believe the basic commands will be similar.

Open image > duplicate. 

Close the original file.

Drag the layers palette out of the palette dock so it doesn't keep disappearing into the palette well.

Double click the image background in layers palette and convert to layer. Re-name this layer Red. 

Duplicate > duplicate layer. Do this twice. Name these layers Green and Blue as you create them.

You now have an image with three active layers, Red, Green and Blue, and no background layer, they can all be adjusted.

Select the Red layer to work on and hide the other two in the layers palette. 

Ctrl+L to bring up the levels dialog. 

In the drop down box select in turn the Green and Blue channels. Remove the colour in each by dragging the slider at the right in the bottom box, the output levels, fully to the left, to zero, 0. So both the output levels are at zero for both these layers. The result will be as you see below. All that remains is the Red channel colour in the Red layer.

Click OK.

Now bring up the hue/saturation menu, Ctrl+U.

With the channel box set to RGB, de-saturate. Move the slider to -100. The layer now becomes just greyscale in tone. But looks very flat, very low contrast. 

Click OK.

Ctrl+L to bring up the Levels dialog again and alter the sliders to give the layer a better contrast level. Don't be tempted to move the sliders right to the edge of where it is indicated the levels actually start. Certainly not for the white end, the highlights. This can burn them out, even though it seems that there is no information there. We generally find you need to move it about half to three quarters of the way along. When your happy click OK.

Repeat this general procedure for the remaining two layers. Removing the colour information from the channels that the layer is not named after. So as we removed the green and blue from the red layer to start with, for the green remove the red and blue, and the blue, the red and green.

Eventually when you have worked through all of this, and it gets quicker the more times that you do it, you will end up with three active layers, Red, Green, and Blue, each de-saturated, but with channel information from each of their respective colour channels, the one's they are named after.

Now you can play to your hearts content. Switching channels 'off', so they are not visible, or choosing opacity from the drop down menu and reducing it. You must keep at least one active layer with 100% opacity if the effects are to be clearly seen. If not, and you can set the percentage as you would in a channel mixer, so it adds up to 100% from all three channels, then you cannot see the results until you flatten the layers and re-apply contrast in levels.

Altering the opacity in the channels sometimes has a huge effect, and sometimes no effect at all. Say you have the red and blue channels active. Changing the opacity of the red channel has no effect, but changing the blue does. The changes and effects that you can obtain this way are varied, and like any monochrome image depend to a large extent on the colours that exist in the image in the first place, just as it would if you were using coloured filters to make changes at the image taking stage.

Here is a colour image, and some monochrome variations we obtained with it using the above technique.