There is more than one way to remove colour
Discarding colour is a choice about which of several answers you want, and the mode is that choice.
- Luminance weights the channels for how bright the eye finds each — green counts for far more than blue, red sits in between. This matches how a monochrome photograph looks and is the right default for photographs, every time.
- Average treats all three channels equally. Simpler, flatter, and it loses the tonal separation that makes a black and white image read.
- Lightness takes the midpoint between the brightest and darkest channel, giving a softer, lower-contrast result.
- Threshold abandons grey entirely and pushes every pixel to black or white against a cut-off.
The [msm_tool slug="black-and-white"] applies brightness and contrast after the conversion, which is the correct order — adjusting a colour image and then discarding the colour throws the adjustment away.
Why luminance and average differ so much
A pure red and a pure blue have identical average values — both are one channel at full and two at zero. Under an average conversion they become the same grey.
To the eye they are nothing alike: red is considerably brighter than blue. Luminance weighting reflects that, so red converts to a light grey and blue to a dark one, and the two stay distinguishable.
This is why an average conversion of a colourful image looks muddy and undifferentiated. Objects that were obviously separate merge into one tone.
Monochrome needs more contrast than colour
Colour does a great deal of work separating objects that have similar brightness. Remove it and those objects merge.
That is why a straight conversion almost always looks flat, and why the fix is contrast rather than a different conversion mode. Expect to raise it further than feels right on the colour original — a good black and white image typically has a fuller tonal range than its colour counterpart, with genuine blacks and genuine whites rather than a band of greys.
Threshold is for line art
Every pixel becomes one of two values. That destroys photographs and is exactly right for logos, signatures, scanned drawings and anything being prepared for a stencil, a laser cutter or a single-colour print.
Adjust the cut-off until the strokes hold together without the background breaking up. On a scan with uneven lighting there may be no single value that works across the whole page — at that point the answer is to fix the lighting in the scan rather than to keep moving the threshold.
Sepia is a look, not a restoration
It converts to grey and then tints warm, which makes a modern photograph resemble an old one.
It does nothing for an actually old photograph. Those usually need contrast and dust removal; adding more brown to a faded print makes it worse. Sepia is a stylistic choice on new work, not a repair for old work.
What black and white is good for
- Unifying inconsistent photographs — different cameras, lighting and days stop mattering when colour is removed.
- Emphasising form and texture, which colour often competes with.
- Portraits, where skin tone variation and background colour distract from expression.
- Printing on a single-colour press, where the conversion is happening anyway and you may as well control it.
Keep the original
The colour information is discarded and cannot be recovered from the result. Always work from a copy — not least because a black and white treatment that looks right today frequently wants revisiting.