Resource Cheatsheet
A+ Core 1 3.1: Display Attributes
Professor Messer A+ 220-1201 objective 3.1 — pixel density and PPI maths, refresh rate vs FPS and V-sync, resolution and aspect ratio, and colour gamut percentages.
- Updated
- Reading time
- 5 min read
- Detail
- A+ Core 1
- Detail
- Display Attributes
On this page
In one line: pick the display from the job — pixel density for sharpness, hertz for motion, resolution and aspect ratio for how much fits on screen, and colour gamut percentages for anything colour-critical.
Companion to: Professor Messer, CompTIA A+ 220-1201 Core 1, objective 3.1 (Display Attributes). The full version is the Display Attributes class notes; the section overview is the Section 3 sheet.
Match the spec to the job
| Use | What matters |
|---|---|
| Gaming, sport | High refresh rate (Hz), fast response |
| Graphics, video editing | Colour gamut, panel type (IPS/OLED) |
| Video watching | Resolution, colour |
| Lobby signage | Size and brightness — PPI barely matters at distance |
| Presentations | Resolution, viewing angle |
Pixel density (PPI)
| Point | Detail |
|---|---|
| What | Pixels per inch of display area (or per cm outside the US) |
| Why | Higher PPI = sharper, crisper image |
| Maths | horizontal pixels ÷ width in inches |
| Trap | Advertised size is the diagonal, not the width |
| Printing | Check the printer’s DPI separately — different measurement |
| Display | Width | Pixels across | PPI |
|---|---|---|---|
| 27-inch 4K monitor | ~24 in | 3,840 | 160 |
| 65-inch 4K TV | ~57 in | 3,840 | 67 |
Same resolution, very different sharpness — resolution alone says nothing about clarity.
Refresh rate
| Term | Meaning |
|---|---|
| Hertz (Hz) | Cycles per second — how often the display redraws |
| FPS | Frames per second — how many images the content supplies |
| V-sync | Locks frame rate to refresh rate, so Hz = FPS |
| Stutter | Motion looks jerky when the refresh rate can’t keep up |
| Content | Typical FPS |
|---|---|
| Films (US) | 24 |
| TV shows, online video | 30 |
| Sport, gaming | 60+ |
The whole chain must support it — display and graphics card and cable/port:
| Connection | Capability (per the lesson) |
|---|---|
| HDMI 2.1 | 4K at up to 144 Hz (uncompressed headline is 4K120; 144 Hz uses DSC) |
| DisplayPort 2.1 | Dual 4K displays, each up to 144 Hz |
144 Hz monitor stuck at 60 Hz? Check, in order: cable → which port → graphics card → OS display settings → the monitor’s own high-bandwidth input mode.
Resolution and aspect ratio
| Standard | Pixels | Note |
|---|---|---|
| HD (1080p) | 1,920 × 1,080 | 2,073,600 pixels |
| 4K | 3,840 × 2,160 | 8,294,400 — four times HD |
- Most standards are 16:9 (1,920÷1,080 and 3,840÷2,160 both reduce to 16:9).
- Some displays use non-standard resolutions or other ratios (ultrawide 21:9).
- Aspect ratio from a resolution: divide both numbers by their greatest common divisor.
Colour gamut
| Point | Detail |
|---|---|
| What | The range of colours a display can reproduce — the eye sees far more |
| Measured on | The CIE 1931 colour space; each standard is a triangle on it |
| Standards | sRGB (Standard Red Green Blue) · Adobe RGB · ITU / Rec. 709 · DCI-P3 |
| On the spec sheet | Percentages, e.g. 100% Rec. 709 / 100% sRGB / 98% DCI-P3 |
| Reading it | Higher % = closer to that standard. 95% sRGB fine for email; colour work wants 100% |
| Best gamut | OLED generally beats LCD; among LCDs, IPS (some variants reach deeper blacks and higher sRGB coverage) |
🔐 Security notes
- High PPI makes shoulder surfing and camera capture easier — sharper screens stay legible from further away.
- Lobby signage is an unattended endpoint: the media player behind it needs unique credentials, patching and an isolated VLAN.
- Unexplained resolution or refresh-rate changes are usually a cable or driver fault — but confirm that rather than assuming, since remote-control tools cause the same symptom.
- Resolution and colour depth feed browser fingerprinting — an unusual combination makes a user more identifiable.
- A cheap “HDMI 2.1” cable that negotiates a lower mode is the small version of a general rule: verify what the hardware does, not what the box claims.
Practice drills
1. How do you calculate PPI, and what's the trap?
Horizontal pixels ÷ width in inches. The trap: advertised size is the diagonal, so convert to width first.
2. Why does 4K look sharper on a 27-inch monitor than a 65-inch TV?
Same 3,840 pixels over a much bigger area: ~160 PPI vs ~67 PPI.
3. Hz vs FPS, and what links them?
Hz = how often the display refreshes; FPS = how many images the content has. V-sync locks them together.
4. Typical frame rates for film, TV and gaming?
24 / 30 / 60+ FPS.
5. You buy a 144 Hz monitor. What else must support 144 Hz?
The graphics card and the connection type (cable and port) — e.g. HDMI 2.1 or DisplayPort 2.1.
6. How many more pixels does 4K have than HD?
Four times — twice as many across and twice as many down.
7. What is the CIE 1931 colour space used for?
Plotting what the human eye can see, so each display standard’s coverage (sRGB, Adobe RGB, DCI-P3) can be drawn on it and compared.
8. 100% sRGB vs 95% sRGB — when does it matter?
For graphics and video editing, yes. For web and email, 95% is fine.
Key takeaways
- PPI = pixels ÷ width in inches; the advertised size is the diagonal. Same resolution ≠ same sharpness.
- Hz is the display’s refresh rate, FPS is the content’s; V-sync ties them. 24 film / 30 TV / 60+ gaming.
- The card and the cable must support the refresh rate too — not just the monitor.
- HD 1,920 × 1,080; 4K 3,840 × 2,160 (four times the pixels); most standards are 16:9.
- Colour gamut is quoted as % of sRGB / Adobe RGB / Rec. 709 / DCI-P3 on the CIE 1931 space; OLED generally widest.