{"course":{"slug":"image-editing","title":"Editing an Image","url":"https://addaly.com/learn/image-editing","level":"beginner","track":"create"},"lesson":{"slug":"black-and-white-properly","title":"Monochrome is a decision about which colours become which greys","url":"https://addaly.com/learn/image-editing/black-and-white-properly","position":36,"of":78,"minutes":9,"answer":"Monochrome conversion is a choice of how each hue maps to a grey, so the six-channel Black and White adjustment reproduces the old coloured lens filters.","keyIdea":"Monochrome conversion is a choice of how each hue maps to a grey, so the six-channel Black and White adjustment reproduces the old coloured lens filters; and a photograph whose subject and background differ in hue but not in lightness cannot be separated by any conversion."},"body":{"format":"markdown","text":"## Desaturate is the one method that throws the decision away\n\nDragging saturation to −100 collapses every colour to a grey determined by its lightness alone. Two objects of different colours but similar lightness become the same grey, and the picture goes flat. That flatness is what people mean when they say their black and white conversions look dull.\n\nThe realisation that fixes it: in monochrome, you choose the mapping. A red flower can be near-white or near-black in the same photograph, depending on how you weight the channels, and both are legitimate. Colour photography records what was there; monochrome conversion is an interpretation, and the interpretation is the work.\n\n## The Black and White adjustment, and the filter it imitates\n\nA Black and White adjustment layer gives you six sliders (reds, yellows, greens, cyans, blues, magentas) each controlling how bright that hue becomes in the result.\n\nThis is a digital version of a hundred-year-old technique. Film photographers screwed coloured glass filters onto the lens:\n\n- **A red filter** passes red and blocks blue, so a blue sky records as very dark and clouds leap out white. Every dramatic Ansel Adams sky is a red or deep-yellow filter.\n- **A yellow filter** is the mild version, the standard landscape default.\n- **A green filter** lightens foliage and is traditional for portraits of men, because it darkens the reds in skin and emphasises texture.\n- **An orange filter** lightens skin and suppresses freckles and blemishes, which is why it was used for portraits of women in the studio era.\n\nThe sliders do the same thing after the fact, and better, because you have all six at once rather than one piece of glass.\n\nThe targeted adjustment tool works here too: click it and drag directly on the sky to darken it, on the skin to lighten it. Far faster than guessing which slider governs a given object.\n\n## The trap: darkening a channel to nothing\n\nPull the Blues slider hard negative to get a dramatic sky, and watch the sky's noise. You are amplifying the difference between the channels, and the blue channel is the noisiest. A strong negative blue on a high-ISO photograph produces a grainy, blotchy sky.\n\nThe same move on an 8-bit JPEG produces banding, because you are stretching a channel with 256 levels across a wider range of greys. Black and white conversion benefits from 16-bit more than almost any other operation, and from starting in a raw developer where the channels still hold their full precision.\n\n## Contrast in monochrome is the whole subject\n\nWithout colour, the only thing separating the subject from the background is tone. A photograph where the subject and the background happen to be different colours at similar lightness will not work in black and white no matter how it is converted, because there is nothing to separate.\n\nSo the judgement runs the other way from colour work: **decide whether the photograph has tonal separation before converting**, not after. A quick test is to add a Black and White layer with default settings and look: if the subject vanishes into the background, either one of the six sliders can pull them apart, or the photograph is a colour photograph.\n\nWhat does work in monochrome: strong shapes, texture, directional light, faces, weather, architecture, anything where the interest is in form rather than hue. What does not: a picture whose point was that the sari was that particular green.\n\n## After the conversion\n\nA monochrome image usually needs *more* contrast work than a colour one, because it has lost a dimension of separation and has to make it up in tone.\n\n- **A stronger S-curve** than you would apply in colour, placed above the Black and White layer.\n- **Dodging and burning**, which matters more here than anywhere else. The whole tradition of fine printing is local tonal control on monochrome.\n- **Local contrast** on textures: stone, skin, fabric.\n\n## Toning, and why prints were never neutral\n\nA pure neutral grey print is a modern idea. Silver prints were routinely toned: selenium for a cool purple-black and archival permanence, sepia for warm brown, gold for blue-black. Platinum prints are warm by nature.\n\nDigitally: a Colour Balance or Curves layer above the conversion, shifting the shadows one way and the highlights the other. Warm highlights with cool shadows is the classic split, and a very small amount (five to eight points) is enough. More than that and it stops being a tone and starts being a colour cast.\n\nGIMP does this with *Colours > Colour Balance* after a *Colours > Desaturate > Mono Mixer*, or with a Curves adjustment on individual channels. darktable has a dedicated *monochrome* and *colour balance RGB* pair. Krita has a Channel Mixer filter layer.\n\n## The free paths\n\n- **GIMP**: *Colours > Desaturate > Mono Mixer* gives you channel weights; *Desaturate > Desaturate* offers Luminance, Lightness, Average and Value modes, and Luminance is the correctly weighted one.\n- **darktable**: the *monochrome* module plus *colour calibration* in its grey mode, which lets you set channel weights precisely.\n- **RawTherapee**: a black-and-white tool with channel mixer and preset film-filter emulations.\n- **Photopea**: a Black and White adjustment layer matching Photoshop's.\n- **Snapseed** on a phone has a Black and White filter with a colour-filter control, which is the same six-slider idea in simplified form.\n\n## The honest part\n\nConverting to black and white does not rescue a weak photograph. It is a widespread belief, that a picture which is not working in colour might work in monochrome, and it is true occasionally, when the problem was a distracting colour, and false most of the time, when the problem was the picture.\n\nWhat monochrome does is remove a variable, which makes the remaining ones (light, shape, moment, texture) carry everything. That is why it is a demanding discipline rather than a filter, and why photographers who work in it mostly decide before they press the shutter rather than after."},"check":{"question":"A photographer converts a landscape to black and white and pulls the Blues slider strongly negative to darken the sky. The sky becomes dramatic but visibly blotchy and grainy. What is the mechanism?","options":[{"text":"Negative slider values invert the channel, and inverted channels carry double the noise of positive ones.","correct":false,"tempting":"Invents an inversion: a negative weight reduces that hue's contribution to the grey value rather than flipping the channel."},{"text":"Darkening a hue reduces the exposure of that area, and underexposed regions are always noisier than correctly exposed ones.","correct":false,"tempting":"Borrows a true fact about capture and applies it to a post-capture remapping, which changes displayed lightness without altering the signal-to-noise ratio that was recorded."},{"text":"A strong weight on the blue channel amplifies that channel's contribution, and blue is typically the noisiest channel in a photograph.","correct":true},{"text":"The Black and White adjustment works in 8-bit internally regardless of document depth, so any strong slider move quantises the result.","correct":false,"tempting":"Attributes a real quantisation symptom to an invented internal limit: the adjustment honours the document's bit depth, and banding from 8-bit shows as smooth terraces rather than blotchy grain."}]},"prev":{"slug":"hue-saturation-and-vibrance","title":"Saturation is a slider that destroys detail quietly","url":"https://addaly.com/learn/image-editing/hue-saturation-and-vibrance"},"next":{"slug":"colour-grading-and-luts","title":"A look is a mapping, and a LUT is a table of it","url":"https://addaly.com/learn/image-editing/colour-grading-and-luts"},"authorship":"Founder and series editor: Dr Mustafa Mun. Written by AI models to a written standard. Exam keys checked blind by a second model: 3,665 of 3,666 agreed. Academic review invited.","review":{"status":"Draft, open for academic review"},"cite":"Addaly (2026) 'Monochrome is a decision about which colours become which greys', in Editing an Image. Edited by M. Mun. Addaly. Available at: https://addaly.com/learn/image-editing/black-and-white-properly (Accessed: 13 October 2026).","licence":{"name":"CC BY-NC-SA 4.0","url":"https://creativecommons.org/licenses/by-nc-sa/4.0/"},"reader":{"schema":1,"title":"Monochrome is a decision about which colours become which greys","courseTitle":"Editing an Image","module":{"index":4,"slug":"tone-and-colour","title":"Tone and colour"},"answer":null,"keyIdea":"Monochrome conversion is a choice of how each hue maps to a grey, so the six-channel Black and White adjustment reproduces the old coloured lens filters; and a photograph whose subject and background differ in hue but not in lightness cannot be separated by any conversion.","hero":{"kind":"plate","image":null,"alt":null,"caption":null},"blocks":[{"t":"h2","id":"desaturate-is-the-one-method-that-throws-the-decision-away","runs":[{"text":"Desaturate is the one method that throws the decision away"}]},{"t":"p","runs":[{"text":"Dragging saturation to −100 collapses every colour to a grey determined by its lightness alone. Two objects of different colours but similar lightness become the same grey, and the picture goes flat. That flatness is what people mean when they say their black and white conversions look dull."}]},{"t":"p","runs":[{"text":"The realisation that fixes it: in monochrome, you choose the mapping. A red flower can be near-white or near-black in the same photograph, depending on how you weight the channels, and both are legitimate. Colour photography records what was there; monochrome conversion is an interpretation, and the interpretation is the work."}]},{"t":"h2","id":"the-black-and-white-adjustment-and-the-filter-it-imitates","runs":[{"text":"The Black and White adjustment, and the filter it imitates"}]},{"t":"p","runs":[{"text":"A Black and White adjustment layer gives you six sliders (reds, yellows, greens, cyans, blues, magentas) each controlling how bright that hue becomes in the result."}]},{"t":"p","runs":[{"text":"This is a digital version of a hundred-year-old technique. Film photographers screwed coloured glass filters onto the lens:"}]},{"t":"ul","items":[[{"text":"A red filter","b":true},{"text":" passes red and blocks blue, so a blue sky records as very dark and clouds leap out white. Every dramatic Ansel Adams sky is a red or deep-yellow filter."}],[{"text":"A yellow filter","b":true},{"text":" is the mild version, the standard landscape default."}],[{"text":"A green filter","b":true},{"text":" lightens foliage and is traditional for portraits of men, because it darkens the reds in skin and emphasises texture."}],[{"text":"An orange filter","b":true},{"text":" lightens skin and suppresses freckles and blemishes, which is why it was used for portraits of women in the studio era."}]]},{"t":"p","runs":[{"text":"The sliders do the same thing after the fact, and better, because you have all six at once rather than one piece of glass."}]},{"t":"p","runs":[{"text":"The targeted adjustment tool works here too: click it and drag directly on the sky to darken it, on the skin to lighten it. Far faster than guessing which slider governs a given object."}]},{"t":"h2","id":"the-trap-darkening-a-channel-to-nothing","runs":[{"text":"The trap: darkening a channel to nothing"}]},{"t":"p","runs":[{"text":"Pull the Blues slider hard negative to get a dramatic sky, and watch the sky’s noise. You are amplifying the difference between the channels, and the blue channel is the noisiest. A strong negative blue on a high-ISO photograph produces a grainy, blotchy sky."}]},{"t":"p","runs":[{"text":"The same move on an 8-bit JPEG produces banding, because you are stretching a channel with 256 levels across a wider range of greys. Black and white conversion benefits from 16-bit more than almost any other operation, and from starting in a raw developer where the channels still hold their full precision."}]},{"t":"h2","id":"contrast-in-monochrome-is-the-whole-subject","runs":[{"text":"Contrast in monochrome is the whole subject"}]},{"t":"p","runs":[{"text":"Without colour, the only thing separating the subject from the background is tone. A photograph where the subject and the background happen to be different colours at similar lightness will not work in black and white no matter how it is converted, because there is nothing to separate."}]},{"t":"p","runs":[{"text":"So the judgement runs the other way from colour work: "},{"text":"decide whether the photograph has tonal separation before converting","b":true},{"text":", not after. A quick test is to add a Black and White layer with default settings and look: if the subject vanishes into the background, either one of the six sliders can pull them apart, or the photograph is a colour photograph."}]},{"t":"p","runs":[{"text":"What does work in monochrome: strong shapes, texture, directional light, faces, weather, architecture, anything where the interest is in form rather than hue. What does not: a picture whose point was that the sari was that particular green."}]},{"t":"h2","id":"after-the-conversion","runs":[{"text":"After the conversion"}]},{"t":"p","runs":[{"text":"A monochrome image usually needs "},{"text":"more","i":true},{"text":" contrast work than a colour one, because it has lost a dimension of separation and has to make it up in tone."}]},{"t":"ul","items":[[{"text":"A stronger S-curve","b":true},{"text":" than you would apply in colour, placed above the Black and White layer."}],[{"text":"Dodging and burning","b":true},{"text":", which matters more here than anywhere else. The whole tradition of fine printing is local tonal control on monochrome."}],[{"text":"Local contrast","b":true},{"text":" on textures: stone, skin, fabric."}]]},{"t":"h2","id":"toning-and-why-prints-were-never-neutral","runs":[{"text":"Toning, and why prints were never neutral"}]},{"t":"p","runs":[{"text":"A pure neutral grey print is a modern idea. Silver prints were routinely toned: selenium for a cool purple-black and archival permanence, sepia for warm brown, gold for blue-black. Platinum prints are warm by nature."}]},{"t":"p","runs":[{"text":"Digitally: a Colour Balance or Curves layer above the conversion, shifting the shadows one way and the highlights the other. Warm highlights with cool shadows is the classic split, and a very small amount (five to eight points) is enough. More than that and it stops being a tone and starts being a colour cast."}]},{"t":"p","runs":[{"text":"GIMP does this with "},{"text":"Colours > Colour Balance","i":true},{"text":" after a "},{"text":"Colours > Desaturate > Mono Mixer","i":true},{"text":", or with a Curves adjustment on individual channels. darktable has a dedicated "},{"text":"monochrome","i":true},{"text":" and "},{"text":"colour balance RGB","i":true},{"text":" pair. Krita has a Channel Mixer filter layer."}]},{"t":"h2","id":"the-free-paths","runs":[{"text":"The free paths"}]},{"t":"ul","items":[[{"text":"GIMP","b":true},{"text":": "},{"text":"Colours > Desaturate > Mono Mixer","i":true},{"text":" gives you channel weights; "},{"text":"Desaturate > Desaturate","i":true},{"text":" offers Luminance, Lightness, Average and Value modes, and Luminance is the correctly weighted one."}],[{"text":"darktable","b":true},{"text":": the "},{"text":"monochrome","i":true},{"text":" module plus "},{"text":"colour calibration","i":true},{"text":" in its grey mode, which lets you set channel weights precisely."}],[{"text":"RawTherapee","b":true},{"text":": a black-and-white tool with channel mixer and preset film-filter emulations."}],[{"text":"Photopea","b":true},{"text":": a Black and White adjustment layer matching Photoshop’s."}],[{"text":"Snapseed","b":true},{"text":" on a phone has a Black and White filter with a colour-filter control, which is the same six-slider idea in simplified form."}]]},{"t":"h2","id":"the-honest-part","runs":[{"text":"The honest part"}]},{"t":"p","runs":[{"text":"Converting to black and white does not rescue a weak photograph. It is a widespread belief, that a picture which is not working in colour might work in monochrome, and it is true occasionally, when the problem was a distracting colour, and false most of the time, when the problem was the picture."}]},{"t":"p","runs":[{"text":"What monochrome does is remove a variable, which makes the remaining ones (light, shape, moment, texture) carry everything. That is why it is a demanding discipline rather than a filter, and why photographers who work in it mostly decide before they press the shutter rather than after."}]}],"check":{"question":[{"text":"A photographer converts a landscape to black and white and pulls the Blues slider strongly negative to darken the sky. The sky becomes dramatic but visibly blotchy and grainy. 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