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Converting color images into black and white

This site (https://northlight-images.co.uk)has had lots of articles related to digital black and white photography for nearly 20 years. Back then the word digital was important, since it was new and a lot of film users (Keith included) were switching over to it.

Now, photography is digital and film a niche. Keith has written this updated guide to digital B&W to look at what has changed and just as importantly what hasn’t. [2004 version]

There is so much more you can do than just ‘remove’ the colour from a photo.

Digital black and white photography​

B&W photography goes back to the very origins of photography and for many years it was photography.

I’ve been interested in black and white ever since printing my first photos in a darkroom at school in the 70’s. My first brush with digital was through scanning, editing and printing my B&W films. Professional photography was kickstarted for me when I got a full frame 11MP Canon 1Ds in late 2003. Since then, it’s been a subject I devote a lot of time to, experimenting and improving my skills. Much of that is documented on this site.
keith_and_pictures

Personally, black and white is perhaps more about showing the structure of a scene. It’s where shadows can become objects in themselves.

For all its beauty though we very rarely get asked for B&W in any of our commercial or architectural work.

The print I’m holding (in ~2005) is one of my first experiments in making large B&W prints. It’s from scanned film, from a visit to Canada in 1992.

The picture on the wall, of aspen tree trunks, is from the 11MP 1Ds, taken in 2004.

However, that’s just my own B&W work. If you’re looking for inspiration search out some of the works of past great photographers. Almost anything you see can be done today with a modern camera and appropriate editing. Well, that and a lot of basic photography skills…

In this article I’m concentrating on the step of making a B&W image from a colour one, since that’s what digital cameras produce.

The fundamentals​

Whilst I generally use the phrase ‘Black and White’ for such photography, I know some prefer ‘monochrome’. I don’t much like toned or tinted images, so my images on screen range from black to white. On paper, they range from the blackest black the printer/ink/paper can manage through to the white of the paper.

The tonal range in the scene you are photographing (light to dark) is likely to be greater than you can capture in a single image and display on a screen. The tonal range of your screen is much greater than you can reasonably print. The actual range in a print depends on the paper type, being wider for glossy papers than matte art papers.

Fortunately, this is way down the line from what I’m looking at here, which is the initial steps in going from colour to black and white.

Two simple approaches​

At this point I should mention two approaches which circumvent some of the complexities in making choices about your B&W image.

The first is just to set your camera to black and white. It will produce B&W images by doing its own conversion from colour, There may be options for ‘film type’ simulation, as well as contrast/tonality settings. This is great for getting a feel for shooting in B&W. You get feedback from the screen and can quickly see how different lighting for colour and B&W changes images.

A very rough guide is that for landscapes, colour shots often look better with the sun behind you, whilst B&W looks better with it off to the side (or even in front). It’s about shadows…

If your camera supports simultaneous recording of RAW and JPEG files, then the JPEG will be in B&W, whilst the RAW file still contains the colour info. Why is this useful? Well, you can use some of the conversion techniques I’ll mention in a bit to produce your own version of the B&W image – tuned to how you want it.

The second easy way…​

Shoot with film, scan it and edit the digital files for printing. I almost hesitate to call this easy any more, since for many photographers, mastering the use of film will need a lot of work. It’s also nowhere near as cheap as it once was and the cost (time and money) per image make it something I’ve no wish to return to. You could go the whole way and print in a darkroom, but my darkroom is long gone.

Canon 5Ds and Olympus OM-2n 50mm

One of my last film cameras. An Olympus OM2 with 50mm f/1.2 lens, compared to my 50MP Canon 5Ds with a 50mm f/1.4 lens. The Olympus lens is one I still use on my EOS RP [review].
Anyway, back to digital images…

Three channels to one​

For B&W film, the emulsion (light sensitive part) usually consists of small crystals that change when exposed to light. The film is developed/processed and these crystals lead to what we see as a negative. In early plates and films, the emulsion was strongly sensitive to blue light, much less to red. This sensitivity led to a particular way in which different colours were rendered in the greyscale image of the negative.

Later films had a more even response to colours, giving a different look.

The digital sensors of our cameras have pixels that detect light – usually split into three types with stronger sensitivities to red, green and blue light. One way of thinking of this is that your camera records three monochrome images, each primarily of one range of colour.

If you’ve edited images then these three images will be familiar as the red, green and blue channels – which we combine to give what is visible to us as a full colour image. I’ll show some examples of just what this means with the aid of a photo I took in Wyoming in 2004

Splitting the channels​

I’ve taken the colour image and included a standard X-Rite ColorChecker card in it.

wyoming-with-CC

No, I didn’t have one with me in 2004. The ColorChecker Passport is usually in my camera bag these days.
First up, here’s just the blue channel from the colour image.

blue-wyoming-with-CC

There’s lots of blue light in the sky and not much from the orange rocks or green grass.

This is a view you’d get with a strongly blue sensitive film.

Next up, just the green channel – a more balanced look.

green-wyoming-with-CC

This is closer to the look with a panchromatic film, such as started to become more popular in the early 20th century.

Lastly, the red channel.

red-wyoming-with-CC

This is less of a difference to the green channel, but note how the orange rocks now look much brighter.

Of course, if your camera sensor is modified for infra-red response, the colour differences become even more extreme. I’ve looked at an infra-red modified camera a while ago.
This single channel approach is the simplest way of getting a B&W image, but suffers from losing over half your sensor data with a typical camera design. You can get camera with modified ‘monochrome’ sensors, but they tend to be on the pricy side, and you are stuck with B&W.

Just in case the images above didn’t give a feel for the differences, here’s an animated GIF…

mixed conversions Wyoming


Filters are not filters any more​

With film you could use a coloured filter on your lens to modify the colour sensitivity. An orange filter for example would cut blue light and darken skies. This would be great for enhancing clouds, such as this photo from the 1980’s of the beach at Shingle Street on the Suffolk coast.

Shingle Street in Suffolk

However, digital images don’t work the same way. Adding your favourite coloured B&W filters to a digital camera just produces coloured images, which when you convert to B&W just don’t show anything like the strong effects you’d get with film.

These two coloured filters are from a collection I was recently given and tried out on a Canon EOS RP. The orange/green one would be rotated to give more of an effect in the sky for use with film. The one with the hole – still a bit of a mystery to me.

coloured-filters

By all means experiment if you’ve got some laying around, but these ones went back into one of my ‘miscellaneous stuff’ drawers…
All’s not lost though. With a digital image it’s possible to effectively split the red/green/blue image data into lots more coloured channels. These can then have the digital, equivalent of a physical filter applied to them. This means that we can duplicate some of the effects possible with film, along with a host of new ones.

Multiple channels to one​

If I think of my colour image from earlier, I have a number of simple options to convert it to black and white without losing data, as I did with the single channel examples above.

From an ultimate quality point of view it’s much better to work on a Camera RAW file, but I can do this with a JPEG.
  • Simply turn down the colour settings
  • Change the image mode to greyscale
  • Use a built-in greyscale conversion function
The first two blend together the three channels to give a monochrome result, whilst the third effectively blends multiple colour channels.

I’m using Photoshop for my editor, but similar controls will be found in many other photo editing packages. I’ve gone back to the unprocessed original 2004 Canon RAW camera file for this.
The greyscale conversion option usually has multiple sliders.

default-BW

There may be a number of preset options.

filter-options


Here’s the equivalent of a red filter being applied.

Note how the moon is now clearly visible in the darkened sky.

high-contrast-red

Pushing it too far​

The further you push the adjustment, the more chance there is of unwanted things appearing in your image. It’s less likely with a RAW file than a JPEG but at a certain point, things like noise can be troublesome.

The photo was taken with a 2003 camera and with the ‘red filter’ we’re losing a lot of blue light from the sky, and boosting the fainter (and noisier) red channel. That shows up noise and if you look carefully a horizontal stripe of sensor pattern noise nearer the top of this magnified screen shot.

noise-and-banding

This is less of a problem with newer cameras, but still there.

It turns out that there are dozens of methods for converting your images in ways like this. If you’d like to explore more I’ve collected together lots of examples over the years.
An alternative way of doing the conversion is with a specialist plugin for your editing software.

The plugin route​

Plugins add functionality to your image editing package. There are a lot I’ve reviewed over the years, but for black and white, one of my favourites has long been Nik Silver Efex Pro. As well as basic conversions, it has lots of preset looks that are worth experimenting with just to get the hang of the many adjustments and settings it offers.

silver efex pro 2

I’ve detailed reviews, with lots of examples, including the recent 2020 update to the DxO Nik Collection which now contains Silver Efex Pro 2

The best technique?​

There isn’t one. It depends on the source image and what you want to do with it. I always start with a simple basic conversion to greyscale to get a feel for how the image will look. Then I look at how different elements of the scene and their colours. Differences in colour can be emphasised as tonal differences using the colour channel sliders in the basic conversion.

I’m always wary of trying to do too much in one go, so whilst the banding is a problem in some of my 2004 1Ds images, there can still be issues with modern cameras – especially if you’re working on an image to make a big print.

There’s nothing wrong with going for ‘strong’ settings, just watch that they are not causing problems elsewhere.

Some of the plugins give finer control over local and global contrast, but beware of ‘halos’ surrounding some edges.

I’ve cranked it up in this example, but the effect is something that can ruin an image once I spot it (and can’t not see it any more).

light halos


It’s fixable though.

A touch of HDR​

I’ve a strong dislike for the gaudy ‘HDR Look’ that some use to liven up otherwise uninspiring photos, but found that it can have real uses in black and white.

The most common use for myself is floodlit buildings, where the range of illumination is beyond any camera I’ve used. Taking multiple shots allows for detail in bright areas, and in shadowy parts too.

st_mary_de_castro

St Mary de Castro, Leicester
Just remember that HDR software works well without needing to turn the dials up to 11.

When to stop the adjustments​

Over the years I’ve found that some of my best B&W images needed relatively little complexity in their conversion from colour. A slight darkening of blue skies often helps, alongside a modest boost in local contrast to bring out cloud detail.

Some have benefitted from a few masked curve adjustments after the conversion, more often than not to treat land/sea/skies as areas requiring slightly different edits, or to move the balance of a photo more towards some aspect.

This suggests that stronger B&W images come from deciding to take images for B&W use, with the changes in composition and lighting that brings about.

I’ve several worked through examples going from photo to print that include how and why I edited images. Whilst I use Photoshop, the basic principles apply whatever means you handle your photos.
hood canal in black and white

black and white print

staithes fine art print tutorial


Printing your photos​

It’s no coincidence that all three examples above have ended in making prints.

B&W can look great on a screen, but for me, it’s about making a print. I’ve a paper review coming up where I’ll be looking a lot more at this aspect of photography. However, I’d note that with B&W or colour, mastering printing is an excellent way to improve all your photography. These articles cover it in far more detail…
I hope that’s been of help in showing why B&W photography is still a key part of what I do. If you’ve questions or comments, please do just ask (by email or the comments below).