--- title: "Compare RGB, CMY and HSB models" subject: "Multimedia System" chapter: 3 key: "semester_8/multimedia_system:rgb-cmy-hsb-comparison" source: https://www.bctengineer.com/q/semester_8/multimedia_system/rgb-cmy-hsb-comparison site: BCT Engineering --- # Compare RGB, CMY and HSB models Multimedia System · Chapter 3: Images and Graphics - Asked in: 2076 Bhadra, 11 marks - Video: [Color models (RGB CMY HSI) | Computer Graphics Lectures in Hindi](https://www.youtube.com/watch?v=TYqzwU8pW7s) — Last moment tuitions - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/multimedia_system/rgb-cmy-hsb-comparison - Whole chapter: https://www.bctengineer.com/md/semester_8/multimedia_system/chapter-3 ## Question Comparisons between RGB colour model, CMY colour model and HSB colour model. ## Short answer RGB is additive for screens using red, green, blue light. CMY is subtractive for printing with cyan, magenta, yellow inks. HSB describes colour by hue, saturation, brightness, matching human perception and enabling intuitive adjustment. ## Answer A colour model is a mathematical way of specifying colours. RGB and CMY are device-oriented models (based on how devices produce colour), while HSB is a perception-oriented model (based on how humans describe colour). #### Short description - **RGB:** additive model. Colours are produced by mixing red, green and blue light. Each component is 0-255 (24 bits per pixel, 16.7 million colours). Black is (0,0,0) and white is (255,255,255). - **CMY:** subtractive model. Colours are produced by cyan, magenta and yellow pigments that absorb light from white paper. Relation: C = 1 - R, M = 1 - G, Y = 1 - B. In printing, a black ink K is added (CMYK) since mixing C, M, Y gives a muddy brown. - **HSB:** Hue (colour type, 0-360 degrees on the colour wheel), Saturation (purity of colour, 0-100%), Brightness (value, 0-100%). It matches the way an artist describes colour, for example "a dull dark blue". #### Comparison table | Point | RGB | CMY | HSB | |---|---|---|---| | Type | Additive | Subtractive | Perceptual (cylindrical) | | Components | Red, green, blue | Cyan, magenta, yellow | Hue, saturation, brightness | | Basis | Emitted light | Reflected light, ink absorption | Human colour perception | | Origin | Black | White | Colour wheel / cone | | White | (255,255,255) | (0,0,0) | any H, S = 0, B = 100% | | Black | (0,0,0) | (255,255,255) in theory | B = 0 | | Used in | Monitor, TV, camera, scanner | Colour printers, publishing | Colour picker, image editing | | Intuitive for user | Difficult to adjust a shade | Difficult | Easy: change one value for lighter or more pure | | Device dependent | Yes | Yes | Depends on RGB it came from | | Conversion | Base model; the others are derived from it | From RGB by simple subtraction | From RGB by non-linear formulas | #### Example: orange - RGB = (255, 165, 0) - CMY = (0, 90, 255) - HSB = H about 39 degrees, S = 100%, B = 100% To make the orange darker in HSB, only lower B. In RGB, both R and G would have to be scaled down together to keep the same hue. #### Summary of use RGB for anything shown on a screen, CMY (CMYK) for anything printed, HSB when a person must choose or edit colours easily. #### Conversion formulas - RGB to CMY: C = 1 - R, M = 1 - G, Y = 1 - B (values 0 to 1). - RGB to HSB: B = max(R,G,B); S = (max - min) / max; H is found from which channel is largest, e.g. if R is max, H = 60 x ((G - B)/(max - min)) degrees. - Check with orange (1, 0.647, 0): B = 1, S = (1 - 0)/1 = 1, H = 60 x (0.647 - 0)/1 = 38.8 degrees, which matches the 39 degrees above. #### Which to choose | Task | Model | |---|---| | Programming a display or web colour | RGB | | Sending a design to a printer | CMY / CMYK | | Designing a colour scheme, adjusting shade or tint | HSB | None of them is better in all cases; the colours must be converted when an image moves from screen to paper, and some bright screen colours cannot be printed. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which statement about RGB and CMY is correct? A. RGB is subtractive and used for printing; CMY is additive and used for screens B. Both are additive models C. RGB is additive (emitted light) and used for screens; CMY is subtractive (ink absorbing light) and used for printing D. Both are perception-oriented models like HSB Answer: C. RGB mixes emitted light; CMY inks absorb light from white paper. HSB is the perception-oriented model. (Key point: Additive vs subtractive) 2. A pixel has RGB = (1, 0.647, 0) in the 0-1 range. What is its CMY? A. (0, 0.353, 1) B. (1, 0.647, 0) C. (0, 0.647, 1) D. (1, 0.353, 0) Answer: A. C = 1 - R, M = 1 - G, Y = 1 - B gives (0, 0.353, 1), i.e. (0, 90, 255) in 0-255 scale. (Key point: RGB to CMY) 3. To make an orange colour darker, what does the answer say to do in HSB versus RGB? A. HSB: change all of H, S and B; RGB: lower one value B. Both need all three values changed C. HSB: lower only B; RGB: change all three values together D. HSB: lower only H; RGB: lower only R Answer: C. HSB matches how humans describe colour, so darkening is one value (B); in RGB all three must change together. (Key point: Why HSB is intuitive) 4. In RGB to HSB conversion, how are B and S found? A. B = max(R,G,B); S = (max - min)/max B. B = min(R,G,B); S = max - min C. B = (R+G+B)/3; S = max/min D. B = 1 - R; S = 1 - G Answer: A. Brightness is the largest channel and saturation is (max - min)/max; hue comes from which channel is largest. (Key point: HSB conversion) ## Related in Multimedia System - [RGB versus CMY colour model](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Argb-vs-cmy) — Multimedia System, chapter 3, asked 3× - [HSB versus YUV colour model](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Ahsb-vs-yuv) — Multimedia System, chapter 3, asked 2× - [CMYK colour model and application](https://www.bctengineer.com/question.md?key=semester_8%2Fmultimedia_system%3Acmyk-colour-model) — Multimedia System, chapter 3 ## Related in other subjects - [Compare software models; propose a fourth model](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Asw-models-compare-fourth) — Instrumentation II, chapter 9