Black and white photo

Not just an on/off switch: adjustable intensity

Most converters only offer "color" or "black and white." Here the slider blends the two versions pixel by pixel: at 60–80% you get the desaturated, cinematic look where colors are barely hinted at, while at 100% you get pure grayscale. It's the same principle as the saturation control in photo-editing software, with nothing to install.

How the gray is calculated

Each pixel isn't simply averaged: the conversion uses perceived luminance (roughly 21% red, 72% green, 7% blue), the standard that mirrors how sensitive the human eye is to each color. That's why skies don't go flat and faces keep their natural contrast. The download is produced at the photo's original resolution, with no resizing.

Why grey is not the average of the three colours

If you took the arithmetic mean of red, green and blue, a bright red and a bright green would give the same grey, and the photo would lose all structure. The eye, however, does not see the three colours with equal strength: it is very sensitive to green, less to red, hardly at all to blue. The conversion therefore uses perceived luminance, weighting red about 21%, green 72% and blue 7%.

It is why in a black and white photo a blue sky goes almost black and a green meadow stays light. And it is also why black and white portraits work: skin is rich in red and green, and keeps its modelling.

When a photo gains from losing colour

When colour distracts instead of telling the story: an interesting subject in front of a yellow billboard, a scene where the colours are dull or muddled, a photo taken under lights of different temperatures that no white balance rescues. In black and white the photograph goes back to being made of light, shadow and shape.

And when there is plenty of contrast: backlight, hard shadows, geometry, texture. The photographs that lose out, instead, are those where the subject stands out from the background only by colour: a red flower in a green meadow, in black and white, becomes a grey patch inside another grey patch.

The adjustable intensity, and what it is for

Between full colour and pure black and white there is a useful band almost nobody uses. Around sixty to eighty per cent you get a desaturated photo, in which the colours stay barely hinted at: it is the look of reportage photography and of much modern design, and it works well when colour serves as context but must not lead.

A low value, on the other hand, is not a mistake: taking away ten or twenty per cent of saturation softens photos taken with recent phones, which tend to overdo colour. Often that is all it takes for an image to stop looking artificial.

What this conversion does not do

It does not simulate the coloured filters of film photography, which were the real black and white tool: a red filter darkens the sky and lifts the clouds off it, a yellow one softens, a green one lightens foliage. In digital the equivalent comes from mixing the channels with different weights, which is what editing software does with the channel mixer.

And it does not add contrast: a flat colour photo stays flat in black and white, indeed looks flatter, because there is no colour to separate the areas. Black and white photographs that work almost always have deep blacks and clean whites, that is a stronger curve than the one they started with.

Nearby tools

For the palette of a colour photo there is Dominant colours from a photo, to blur a background Blur part of a photo and to write on it Write on a photo. For dimensions and size Resize photo and Compress image.