Strong black and white

Learning goal

You will be able to turn a color photo into a strong black and white, not just by deleting the color, but by choosing one by one the gray each color will fall to. You will explain why setting saturation to zero often gives a flat result through the luminance trap, in which different colors fall to the same gray when they have the same brightness. You will see how the color sliders and the channel mixer, which blends the three color channels in different proportions, work in black-and-white conversion, and how channel weight changes the gray values and the overall brightness. You will notice the edge tearing that appears at color boundaries when you push the sliders, build contrast after conversion with the tone curve and dodge and burn, and optionally give a warm or cool mood with toning. You will check on different skin tones how the choice of channel changes skin's texture and lightness.

The question

The album's inside booklet will be printed without color. The drummer opens the courtyard frame and pulls saturation down to zero. The result isn't the strong black and white they expected; it is a pale, flat, muddy heap of gray. The tile color of the wall and the blue of the afternoon have dropped to almost the same gray tone, and the boundary between them has disappeared. The faces, too, have merged with the concrete wall behind.

When they open the program's black-and-white panel they see eight separate color sliders. When they pull blue down, the sky darkens and separates from the bricks; when they pull orange up, the faces brighten. But when they pull blue too far, this time a strange, bright strip appears along the line where the brick wall touches the sky. How do you make a good black-and-white photo? What is the difference between deleting color and turning color into gray?

Context

You saw earlier how to think in black and white: that when color is removed from a scene, light, shadow, shape and texture remain; how colored filters managed the grays in the film era; and how the color sliders take over this job in editing (Lesson 11.7). This lesson builds on that foundation and deepens the editing side: the logic behind the color sliders, the channel mixer, the limits of conversion, and the contrast and tone work that comes after conversion.

A strong black and white is not a colorless copy of a color photo; it is rebuilding with gray tones the distinctions the colors carried. In the color photo, what separated two objects was their colors; in black and white, only different gray values can build the same distinction. That is why converting to black and white means rethinking the photo.

Simple explanation

Why isn't deleting color enough?

Setting saturation to zero, or turning a photo into a ready-made gray tone, converts each color to gray only according to its own brightness. The luminance trap is two areas whose colors are very different from each other but whose brightness is close falling to the same gray in this conversion, and the distinction between them being lost. A tile-colored wall and a blue sky separate sharply from each other in a color photo, because the eye sees the color difference. But if their brightness is close, when the color is deleted two areas of the same tone remain and the photo goes flat.

The way out of this trap is to decide yourself how each color will turn into gray. The color sliders in the black-and-white panel do exactly this: each slider decides how light a gray the areas of that color will fall to. This is the black-and-white counterpart of the luminance sliders you saw in the HSL lesson; the only difference is that here the color itself doesn't show in the result.

How does the channel mixer work?

A channel mixer is a tool that creates the black-and-white image by blending the photo's three color channels in different proportions. Each channel of a color photo is like a separate black-and-white image showing how much light there is in that color. In the red channel, red and orange objects look light and the blue sky dark; in the blue channel, the opposite. The channel mixer produces a single black-and-white image by mixing these three images in the proportions you want.

Channel weight is the percentage at which a channel takes part in this mix. Raising the red channel's weight gives a result similar to the red filter of the film era: the sky darkens, skin and red objects lighten. Raising the blue channel's weight, on the other hand, lightens the sky and makes fog and haze more pronounced. When the total weight of the three channels is kept at about one hundred percent, the photo's overall brightness is preserved; when the total goes above one hundred percent the photo brightens, and when it drops below, it darkens. The color sliders are often easier to use; the channel mixer, on the other hand, shows the logic of the film-era filters more directly.

Where do the sliders break down?

Edge tearing is the bright or dark strips, halos and noise that appear at the boundaries where two different colors touch each other, when a color slider or a channel weight is pushed too hard. When you pull the blue slider down too far, the sky darkens, but at the boundary between the sky and a tree, a building or a brick wall, a thin halo or a tear appears because the colors don't separate completely. The same pushing also increases banding and noise in wide areas such as the sky. Not taking the sliders to the extremes, darkening an area that needs pushing separately with a mask, and checking the result by enlarging the edges prevent this problem. The problem isn't specific to the sky; the same tearing can appear at every boundary where a red sign touches green leaves or an orange garment touches a blue wall, which is why once the conversion is done, going over the photo once along the color boundaries is a good habit.

What do you do after conversion?

The color sliders decide where the grays sit relative to each other; the photo's real strength, on the other hand, is built after conversion. With the tone curve you make sure the blacks are really black and the whites really white, and place contrast in the midtones where you want it. With dodge and burn you bring forward again a face or an object that stood out through color difference in the color photo but got lost in black and white. Doing all this work with adjustment layers that preserve the original color photo lets you go back to color whenever you want.

Toning is giving a black-and-white photo a single, light color across the whole of it; a warm brown tone reminiscent of old prints or a cool bluish tone are the best known. With the split toning from the color grading lesson, it is also possible to paint the dark and bright tones in two separate colors. Toning is an aesthetic choice; kept light it adds a warmth or a coolness to the photo, kept strong it hides the photo behind a color filter.

The choice of channel directly changes how skin looks. The red channel lightens skin and softens redness and spots, because in red light these marks separate little from the skin around them. The blue channel, on the other hand, makes spots, pores and irregularities in skin more pronounced. On light skin, a conversion with a high red weight can easily turn the face into a stark white, textureless surface; to preserve detail, you need to lighten orange and red in moderation. On dark skin, on the other hand, darkening orange and red too much drops the face into a detailless black, and lightening them too much pushes the skin toward gray and flatness; the goal is for the skin to stay in its own tonal place and with its texture. If people with different skin tones are in the same frame, a slider can protect one while spoiling the other; then you need to adjust each face separately with a person mask. Black and white is not a tool for erasing or changing the difference between skin tones.

Visual evidence

The drummer converts the factory courtyard photo with a black-and-white adjustment layer, without touching the color master file. At first the sliders are in the middle; the bricks and the sky have dropped to the same gray. They pull the blue slider down by a moderate step; the sky drops to a dark gray and separates from the brick wall. They raise the red slider a little; the bricks lighten and their texture becomes pronounced. When they push the blue slider one more step, a bright strip appears along the line where the wall touches the sky; they undo the step and darken the sky separately with a gradient mask, and the strip disappears.

Then they move to the faces. When they pull the orange slider up, the keyboardist's light skin is almost stark white and textureless; the bassist's dark skin, on the other hand, still merges with the wall. They bring orange to a moderate place and lighten the bassist's face separately by half a stop with a person mask; on the shadow side of their face, the shape of the cheekbone and the texture of their beard can be made out. With a tone curve they settle the blacks and whites into place and add a very light warm toning. The photo is no longer a pale copy of the color photo; the bricks, the sky and the four faces each separate in their own gray.

Common mistakes

Summary

Setting saturation to zero turns each color to gray only according to its own brightness; in the luminance trap, different colors fall to the same gray and the photo goes flat. The black-and-white panel's color sliders and the channel mixer, which blends the three color channels in proportions, let you decide each color's gray separately; channel weights change the gray values and the overall brightness, and if the sliders are pushed, edge tearing appears at color boundaries. After conversion, the photo's strength is built with the tone curve, dodge and burn and optional toning; the choice of channel changes skin's lightness and texture, which is why each skin is checked separately and black and white isn't used to change the difference between skin tones.

Mini assignment

In this assignment you will convert a color photo to black and white in three different ways and compare them; choose a photo with sky, objects of different colors and at least one person in it.

1. First convert the photo only by setting saturation to zero; find two areas that were separate in the color photo but fall to the same gray in black and white.
2. Convert the same photo with the black-and-white panel's color sliders; adjust each color's gray so as to separate the sky, the objects and the face from each other.
3. With a channel mixer, do a red-weighted conversion once and a blue-weighted conversion once; note how the sky and the skin change, and keep the total weight close to one hundred percent.
4. Add a tone curve and a light toning to the best version; check by enlarging the edges of the places where you pushed the sliders whether there is edge tearing.

Check yourself

• Can you predict in advance which colors in a color photo will fall to the same gray in black and white?
• Can you explain the difference between the color sliders and the channel mixer?
• Did you check separately how the black-and-white conversion affects the lightness and texture of each skin in the frame?

Glossary

Mini quiz

1. Why can red bricks and a blue sky fall to the same gray when saturation is set to zero?

• A) Because their brightness is close to each other
• B) Because the bricks reflect the sky
• C) Because the white balance is wrong
• D) Because red and blue are the same color

2. What happens if the total weight of the three channels in the channel mixer goes far above one hundred percent?

• A) The photo darkens
• B) The colors come back
• C) The photo's overall brightness increases
• D) Only the sky changes

3. When you pushed the blue slider very hard in black-and-white conversion, a bright strip appeared at the boundary between the sky and a building. What is this called and what is the fix?

• A) The luminance trap; set saturation to zero
• B) Edge tearing; undo the slider and darken the sky separately with a mask
• C) Banding; change the white balance
• D) Channel weight; raise red

4. In a black-and-white group photo, the orange slider makes a light-skinned person's face stark white while a dark-skinned person's face merges with the wall. Which is the most fitting fix?

• A) Lightening the orange slider even more
• B) Turning the photo back to color
• C) Reducing the contrast of the whole photo
• D) Bringing orange to a moderate place and adjusting the dark-skinned person's face separately with a person mask

Answers

1. A — When color is deleted only brightness remains; areas with close brightness fall to the same gray.
2. C — When the total weight exceeds one hundred percent, extra light is gathered from the channels and the photo brightens.
3. B — A pushed slider creates tearing at the color boundary; adjusting the area separately with a mask prevents it.
4. D — A single slider changes both skin tones together; the mask keeps each face in its own tone.

Summary card

• Setting saturation to zero isn't enough; watch out for the luminance trap.
• Decide each color's gray separately with the color sliders and the channel mixer.
• The total of the channel weights changes the overall brightness.
• Don't push the sliders; look for tearing at color boundaries.
• After conversion: curve, dodge and burn and toning; check each skin separately.

Bridge to the next lesson

When the black-and-white inside pages were done, the band made one last request: in one version of the cover, behind the four members, instead of the concrete wall in the courtyard, the lights of a concert hall where the band has played on stage should show. The drummer had the courtyard photo and a photo of an empty concert hall they had shot on a separate day. Combining the two looked like a mask job, but if the directions the light came from, the colors and the perspective didn't match, the result would turn into a collage. How do several photos combine into one scene? The next lesson tells about masks, matching light direction and honestly labeling a combined image.