There are at many ways to convert an image from color to black and white. Here's a roundup and evaluation of the top seven plus a set of considerations to help you choose the best one for your needs.
Desaturate or use the Saturation slider to make all the channels the same without control over the mix. Desaturaton is useful for near neutral images, otherwise it produces compressed tonal structure.
2 Convert Mode To Grayscale
Grayscale conversions eliminate all channels but one. The default mix is 59% Green, 29% Red, 11% Blue. This can be customized by targeting a single channel before conversion, to get 100% of any channel in any color space, including Lab. Quick and direct, this method eliminates future flexibility; its limited use is to create Grayscale images for reproduction but it's not the best way to make a conversion from color to black and white.
3 Channel Mixer
The Channel Mixer set to Monochrome allows you to customize the mix of channels and can be used as an adjustment layer, which allows you to change the mix at any time in the future.
In the vernacular the phrase “black and white” can be used to describe definitive answers, while the use of the phrase “gray areas” often means an area defies easy definition making it difficult to draw hard and fast lines.
While there is a general consensus as to what constitutes the colors black, white and gray, opinions vary significantly when it comes to identifying absolute blacks, whites, and grays.
Which of these colors is absolutely neutral? Which are warmer than neutral? Which are cooler than neutral? All of them are nearly neutral when compared to fully saturated colors. More importantly, which colors do you prefer? Which colors would most enhance the images you are producing?
It‘s helpful to sensitize yourself to these many possibilities and to identify your personal preferences.
mid key full scale
mid key high contrast
Most successful artists define a consistent palette for their life’s work, for periods during their careers, or for individual bodies of work. It’s one of the primary things that creates an easily recognizable signature style. This is as true for black and white photographers as it is color photographers.
You can precisely describe black and white palettes by identifying the overall lightness or key (high – light, medium, low – dark) and the amount of contrast (high, medium, low, none) held in three ranges of tones – shadows (zones 0-3), midtones (zones 4-7), and highlights (zones 8-10). Put more broadly, the dominant range of tone is identified first and then each range of tone can be described as expanded or compressed; a range of tone that does not exist in an image could be described as fully compressed.
The division between color and black and white in photography has been overemphasized based on the limitations of 20th century processes. 21st century processes are significantly different and beg a reconsideration of this division. Today, when we make black and white images we typically capture, process, and print with color.
When people use the term black and white they generally mean neutral (without saturation or bias towards one or more hues). Typically the use of the phrase “black and white” also encompasses warm and cold toned monochromatic images, cross-toned duochromatic images, and in some cases subtly tinted polychromatic images. The guiding principle behind these related but varied palettes is an emphasis on luminosity values, along with a restrained use of hue and very low levels of saturation.
Color to black and white conversions are radical transformations of an image. They establish the tonal foundations of a neutral image, creating tonal relationships by determining which areas of an image become light and which are dark. While this process can generate some localized effects (all blues become darker or lighter), this is quite different than selectively lightening and darkening an image to accentuate existing tonal relationships (only select blue areas become darker or lighter). Selectively enhance a tonal structure after conversion, rather than before. Selective enhancement may yield dramatic results.
Here are two ways.