Given that digital cameras actually shoot in color, what’s the best way to convert these color images into black and white? If you set your camera to one of its black and white photo styles and shoot only JPEGs and not RAW files, then the camera itself will do the conversion and you are left with a black and white only image – though you may have some control over the contrast, clarity and even color filter settings. If you do as I do, though, and shoot RAW files, then when you process them on the computer you can choose the conversion method.
I’ll run through two older methods first that you probably wouldn’t use today, just to tick them off the list, as they were once popular approaches.
- Articles in this black and white series
- Why photograph in black and white?
- How to shoot in black and white
- What are the best cameras for black and white photography?
- Converting color photographs to black and white: what’s the best method to use?
1. Convert to grayscale
Photo editors work with images using the RGB color model. This consists of three color channels – red, green and blue. In the old days, the simplest approach to swap to black and white was to change the image to grayscale mode, where there’s only one grayscale channel. This might have been effective and easy to grasp, but does not give you any control over how colors translate into shades of gray. Grayscale mode is rarely used in photography today because it doesn’t support any color information at all, so you can’t apply toning effects to black and white images, for example. Yes, Photoshop did have a Duotone mode which could do this, but the modern approach is to stick with RGB color. Besides, many photo editors don’t even support grayscale mode any more anyway.
2. Desaturate
An alternative method, which keeps the image in the regular RGB color mode, is simply to reduce the saturation to zero. It works. What’s more, if you play some fancy tricks with the white balance beforehand, it’s possible to change the way colors translate into different shades of gray. But this is still not the best way to work because it’s using tools that aren’t really designed for the job and don’t give you the same degree of control that you get from those that are.
3. Channel Mixer
For a long time this was the preferred route for Photoshop users. The Channel Mixer tool isn’t designed specifically for black and white conversions, but it does a good job. It essentially enables you to mix the strength of the red, green and blue color channels in making the black and white images. It is a lot like using color filters on the camera lens, but with all the flexibility of careful software adjustments after the shot was taken. You do have to know what you are doing and if you reduced the strength of one channel to darken that color you have to increase the strength of the others to maintain the overall exposure, but that wasn’t too hard to figure out.
Even so, the Channel Mixer is still a somewhat crude and technical approach. These days, the best photo editors have black and white conversion tools that are designed specifically for these tonal conversions with much subtler color range selections and no exposure compensation needed, so let’s take a look at those.
4. BW mode/Color Mixer controls
Lightroom has a BW mode with sliders for mixing the strengths of different color ranges, while other programs have color mixer controls that do the same thing. These are a little like Photoshop’s Channel Mixer but with many more colors and not just red, green and blue. You can, for example, reduce the strength of blues to make blue skies come out darker in black and white, or increase the strength of greens and yellows to lighten foliage. You can save your favorite color mixes as presets, or the software may already come with a selection of pre-configured ‘filter’ settings, such as red, yellow or orange filter effects in different strengths.
There is a certain amount of finesse needed here. If you apply a strong adjustment to one particular color it’s wise to apply a smaller adjustment to neighboring color ranges so that the effect isn’t too sudden.
It’s also wise to be cautious about big adjustments generally. This comes back to the way sensors record different colors using a color filter array over the sensor’s photosites. With any color filter array, each photosite is sensitive to just one color – red, green or blue. And with the most common ‘bayer’ sensor layout, you get a repeating grid of two ‘green’ photosites, one ‘red’ and one ‘blue’.
The reason for the extra green photosites is that the human eye is most sensitive to image detail in this part of the color spectrum, apparently. In any event, the upshot is that only half the sensor’s photosites are sensitive to green and only one in four are sensitive to red or blue. The camera, or your RAW processing software, will then need to ‘demosaic’ this color information to guess at, or interpolate, full color information for each photosite based on what those around it record.
Now in color photography this doesn’t matter very much because all the color channels blend very successfully and you would never know that any process like this is taking place.
You won’t notice when you convert images to black and white either, UNLESS you use very strong color mixer adjustments that lean very heavily on the red, green or blue color channels. In isolation, these colour channels can look quite noisy under magnification, sometimes with noticeable edge effects around object outlines.
This tends to be most noticeable if you try to replicate the effect of a strong red filter. When you do this digitally, it relies very heavily on the red color channel and suppresses the rest. Remember, only one photosite in four on the sensor is sensitive to red, so your image ends up being interpolated from a very limited set of data.
This only happens if you push your black and white filter adjustments very hard, and some programs are much better at managing this than others. It’s an unavoidable effect from the design of digital camera sensors, so there’s nothing to be done about it except to be vigilant when making strong color mixer/filter adjustments during your black and white conversions.
5. BW presets
Now the black and white conversion methods we’ve looked at so far are quite hands-on manual processes, but you don’t have to get that deep into the technicalities these days because many programs now offer one-click black and white presets.
These will typically apply different color mixing/filter effects anyway, and will often apply contrast, clarity and other adjustments too as part of a distinct black and white ‘look. You shouldn’t dismiss presets as an easy way out for cheaters! The presets bundled with photo-editing applications will typically have been developed by skilled designers and photographers. Lightroom, for example, has some excellent black and white presets right out of the box, as does ON1 Photo RAW. Here’s one I designed myself, which includes a movable mask for ‘relighting’ your images.
The other advantage of presets is that they combine a bunch of adjustments using the software’s own adjustment panels and you can check to see how these have been modified and learn how the effect has been achieved. You’re not dodging the work, you’re actually learning something.
6. B&W LUTs and profiles
Presets are not the only one-click black and white tool. The video world has long uses LUTs (lookup tables) for color conversions and creative color grading, and these have now found their way into photo editing tools. Not all programs support LUTs, but may offer something similar. Lightroom, for example, has a large range of ‘profiles’ which do a similar thing. This is a third-party black and white Lightroom profile from lutify.me.
The difference between LUTs/profiles and presets is that LUTs and profiles are essentially a pre-processing step outside of and before any editing with the software’s regular tools. You don’t have to use them at all, but if you do they change the appearance of the image without involving the regular editing tools – which you can then apply on top of the LUT/profile effect anyway.
LUTs and profiles are a very interesting and effective tool for black and white photographers. Essentially, all the tonal and color filtering options and sometimes even toning or split toning effects are incorporated into the LUT. You don’t have any control over the LUT’s tonal transformations, but LUTs can nevertheless provide a perfect ‘look’ or starting point for your black and white images.
In my opinion, presets, LUTs and profiles are excellent for black and white photography because they can show you a whole range of image treatments you might never have thought of yourself. It’s very easy to get stuck in a rut with your image-editing, and seeing other treatments and ideas can really open your eyes to the different creative styles you could adopt.
Which conversion method is best?
This depends on which method gives you the results you like best, and which one makes the most sense to you both on a technical level and as part of your everyday workflow. I would probably rule out grayscale conversion, desaturation and Photoshop’s Channel Mixer as being rather unsubtle and outdated, but B&W conversion modes, presets and profiles are all great methods.
