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Grayscale Image Converter

Turn a photo black and white with proper luminance weighting.

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Quick Tool Overview

The Grayscale Image Converter uses Rec. 709 luminance weighting rather than a flat average of the channels, which is why skies stay dark and foliage stays light instead of both turning to mud. A channel mixer then lets you push the weighting deliberately, the way a coloured filter did on black and white film.

What it does
Converts a colour photo to black and white
You give it
Any colour image
You get back
A weighted grayscale conversion
Best for
Portraits, documents and print work
Image Tools Free, unlimited use No sign-up Runs in your browser

About the Grayscale Image Converter

Averaging the red, green and blue channels is the naive way to make a photograph grey, and it is wrong: the eye is far more sensitive to green than to blue, so an average turns blue skies into mud and green foliage into grey soup.

The default here uses Rec. 709 luminance weighting, which matches how a monitor and an eye actually work. Beyond that, a channel mixer lets you push the weighting deliberately — heavier red to lighten skin and darken skies, heavier blue for a cold, high-contrast look. That is what a colour filter did on black and white film, and it is still the difference between a flat conversion and a good one.

Key features of the Grayscale Image Converter

Correct luminance weighting

Red 21%, green 72%, blue 7% — the proportions the eye actually uses, not an unweighted average.

Channel mixer

Push red up to lighten skin and darken sky, or blue up for a cold, hard result — the film filter effect, as sliders.

Classic presets

Luminance, red filter, blue filter and high contrast cover the looks people actually want.

Contrast control

Black and white lives or dies on contrast, so it is on the same page rather than a separate step.

Smaller files too

A single channel of variety compresses better, particularly in PNG — a useful side effect.

How to use the Grayscale Image Converter

  1. 1

    Load the photo

    Any colour image. The default conversion appears immediately.

  2. 2

    Try the presets

    Luminance is the neutral choice; red filter, blue filter and high contrast are the classics.

  3. 3

    Mix the channels

    Push red up to lighten skin and darken sky, or blue up for a colder, harder result.

  4. 4

    Adjust and download

    Fine-tune the contrast, then save the black and white version.

Frequently asked questions

Because the eye weights them very differently — roughly 21 percent red, 72 percent green and 7 percent blue. An unweighted average makes blues far too light and greens far too dark.

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