Wrong PPI quotes usually mix three numbers: native resolution (W×H), pixel density (PPI at a stated diagonal), and readability (whether people finish the reading or selection task from the real standing positions). The same resolution on a larger diagonal lowers density. A higher PPI figure alone is not a readability certificate — physical letter size, viewing distance, contrast, layout hierarchy, and a clean playback path all matter.
Four decisions before you compare quotes
- Put diagonal and native resolution on the same quote line. A bare PPI without both is incomplete.
- Record four content-path rows separately: source artwork, application canvas, player output, physical screen.
- Test the smallest critical text from the real standing positions with the intended player output and final layout.
- Retest after content changes. A higher PPI number does not replace appropriate physical letter height.
The 55-inch FHD / UHD examples below are mathematical illustrations — not promises for a specific YJCEN model. After you select the hardware line, use that configuration’s documented native resolution and size. Side-readability is separate — see the LCD viewing angle guide. Colour-range claims are separate — color gamut for commercial displays. Multi-panel seams are separate — LCD video wall bezel size.
Resolution, PPI, and readability answer different questions
| Term | What it answers | What to require on the quote |
|---|---|---|
| Resolution (native) | Pixel count across and down (W×H) for the selected configuration | Native W×H from the selected model documentation |
| Pixel density (PPI) | How many pixels fit into one inch at a stated diagonal | PPI only with diagonal + native resolution both stated |
| Readability | Whether people complete the reading / selection task from the intended positions | Physical letter check with final player output — not a PPI rank alone |
If two screens share the same resolution and aspect ratio, the larger diagonal spreads the same pixels over a larger area and lowers PPI. That matters when one design file runs across a signage network: letter physical height changes with the displayed image size. A layout that looks comfortable on a designer’s laptop still needs a separate check at the install.
Confirm native resolution and install size in the selected configuration documentation and in YJCEN Downloads. Do not add an unverified SKU PPI column to the quote.
How to calculate PPI (illustration only)
For a panel with square pixels:
PPI = √(H² + V²) / diagonal_inches
where H and V are the native horizontal and vertical pixel counts.
Mathematical illustrations (square pixels, nominal diagonals):
| Diagonal | Native resolution | Approx. PPI |
|---|---|---|
| 55 inch | 1920 × 1080 (FHD) | ≈ 40.1 PPI |
| 55 inch | 3840 × 2160 (UHD / 4K) | ≈ 80.1 PPI |
| 75 inch | 1920 × 1080 (FHD) | ≈ 29.4 PPI |
These figures explain the relationship between size and resolution. They are not specifications for any YJCEN model. Doubling both horizontal and vertical resolution at the same physical size doubles PPI and multiplies total pixel count by four — keep those quantities separate when reading a sales description against a panel sheet.
On every quote line, pair diagonal + native W×H. Request or compute PPI only with those two values stated. Verify the selected configuration via the matching product line — for example Digital Signage Totem or indoor digital signage — and Downloads.
Choose screen size around the reading task
Fill the viewing-band column with the project’s actual metres. Use a measured reading task — not a universal minimum-PPI number.
| Viewing band (fill actual metres) | What the density decision answers |
|---|---|
| Near / stop-and-read (wayfinding, counter menus, touch; readers stop at the screen) | Higher PPI can support finer UI and smaller labels only if physical letter height and touch targets still pass the standing check |
| Mid / lobby & gallery (lobby directories, gallery captions) | Balance physical message size with panel resolution. A larger diagonal at the same FHD lowers PPI; letter height rises only if the layout scales text in physical mm — require a content mock at far position F |
| Far / walk-by promo (corridor promo, window from outside; short dwell) | Message length + physical letter size usually dominate over chasing max PPI. A lower-PPI larger image can outperform a dense small panel for the same walking glance |
| Mixed network (one design across sizes / orientations) | One master file is not proof of readability on every size. Approve each supported size / orientation |
Quick A vs B: stop-and-read UI / small labels → higher PPI and a standing letter-height check; lobby directory → physical message size at far position F first; walk-by window promo → message length + letter size (and day/night) over max PPI; mixed network → approve each size/orientation, do not assume uniform scaling.
Confusion table: PPI vs pitch vs resolution vs readability
| Claim | Rule | What to require instead |
|---|---|---|
| “Higher PPI = always easier to read” | False as a blanket rule. PPI relates pixels to physical size. Readability also needs physical letter size, distance, contrast, hierarchy, and a clean playback path. | Diagonal + native resolution + viewing positions + smallest critical text check with the final player output. |
| “4K / a resolution label = readable menu” | No. Resolution is pixel count. A 4K panel can show an unsuitable layout as accurately as a good one. | Bind the quote to native W×H and acceptance content (names, prices, longest strings). Retest after content changes. |
| “Resolution = pixel density” | Different questions. Resolution = pixel count; PPI = pixels per inch at a stated diagonal. Same W×H on a larger diagonal → lower PPI. | Always pair diagonal + native resolution on one quote line. |
| “Supplier gave only pixel pitch (mm)” | Pitch is spacing between pixel centres. With square pixels, pitch (mm) ≈ 25.4 / PPI. Still not a readability certificate. | Ask for diagonal + native resolution (or pitch and resolution + size). Do not copy LED pitch viewing-distance rules onto LCD without a project check. |
| “Print DPI / design-file DPI = on-screen density” | Print DPI labels do not change the LCD pixel grid. | Check image pixel dimensions, app scaling, and panel native resolution separately. |
| “Case-page 4K wall = this model’s default PPI” | Case resolution applies to that install only. | Use the selected panel’s documented native resolution; recompute PPI only with that size. |
Route hardware by task after the table — floor-standing display, self-service kiosk, or window high-brightness display — then lock diagonal + native W×H from that configuration. For walls, also use how to choose an LCD video wall when seams and grid size sit beside the density question.
Why higher resolution does not automatically make text easier to read
A higher-resolution panel can represent finer detail, but the content must use that detail correctly. If a layout keeps the same pixel-sized letters on a denser panel, those letters occupy less physical space. The edges look sharper; the far-position reading task can still fail.
Decide how large the message must appear in millimetres before filling the canvas with more lines. A wayfinding screen needs destination and direction to stand out. Adding more copy because the panel has more pixels works against that purpose.
Physical size conversion (one-to-one mapping)
For a one-to-one image mapping, a block’s width in inches = width in pixels ÷ panel PPI.
Illustration (rounded): a 100-pixel-wide block is 2.5 inches wide at 40 PPI and 1.25 inches wide at 80 PPI. These numbers explain the calculation; they do not specify a recommended text or button size for any YJCEN SKU.
A font’s nominal pixel size is not necessarily the height of its visible letters. Use the actual rendered content when checking text. Letter shapes, stroke thickness, spacing, and contrast with the background all affect recognition.
Same-resolution, different-diagonal illustration: 1920 × 1080 at 55 inch ≈ 40.1 PPI; at 75 inch ≈ 29.4 PPI. The larger screen has lower density, but the same full-screen layout also appears physically larger — which can matter more for a distant viewer than the PPI figure alone. Assess size and viewing arrangement together; do not choose a smaller screen solely because its PPI number is higher.
Content path and pre-order content test
A sharp panel cannot fix a broken content path. Record each row below on the RFQ so artwork, app canvas, player output, and the physical screen do not get compared as one number.
Content path — four rows
| Row | What to record | Why it matters |
|---|---|---|
| Source artwork | Pixel dimensions, colour space, intended safe margins | Oversized or undersized masters force scaling before the panel ever sees the file |
| Application canvas | Design canvas size / orientation template | A laptop canvas is not the install canvas |
| Player output | Output mode, scaling / crop / letterbox rules | Soft scaling can blur fine type even on a dense panel |
| Physical screen | Diagonal, native W×H, orientation, mount height | PPI and letter physical height live here |
Pre-order content test (six steps)
- Load the final files through the intended player and output mode — not only a designer laptop preview.
- Stand at the agreed near / far / side positions (and sidewalk if window).
- Read the smallest critical label, price, or destination string; record pass / fail with position.
- For touch: confirm target size / spacing and application orientation (PPI does not replace touch acceptance).
- For glass / window: run day and night checks.
- Keep content version, output settings, photos of the sample arrangement, and a named sign-off.
Pixel pitch, PPI, and print DPI — keep them distinct
Integrators often receive one of these labels alone. Keep the units and the question each measure answers separate — especially when an LED pitch habit tries to set an LCD menu distance.
| Measure | Unit / form | Use it for | Do not use it for |
|---|---|---|---|
| PPI | pixels per inch at a stated diagonal | Comparing density when size + native resolution are known | A standalone readability certificate |
| Pixel pitch | mm between pixel centres (≈ 25.4 / PPI for square pixels) | LED-style spacing discussions; converting to PPI when size is known | Copying LED billboard distance rules onto LCD menus |
| Native resolution | W×H | Quote line + player output match | Proving letter height without a physical check |
| Print / file DPI | design-software label | Print production | Claiming on-screen density |
Scenarios: wayfinding, menus, touch, window
Finding a direction (near / mid)
Prioritise destination and direction hierarchy over packing more lines because the panel has more pixels. Require a standing check at the farthest normal reading position with the longest destination string. If side approach matters in a corridor, note that angle separately from PPI — use the LCD viewing angle guide. Hardware path: floor-standing display or indoor digital signage.
Reading a menu (near / mid)
Bind acceptance to names, prices, and the longest normal strings — not short placeholder words. Retest when columns or font sizes change. A 4K label does not replace that check. Keep player output mode on the acceptance note so a soft-scaled preview cannot pass in place of the install player.
Using a touch kiosk (near)
PPI is not touch accuracy. Record target size / spacing, application orientation, and glare / glass with the diagonal + native W×H. Run the standing check with the interactive application, not a static mock alone. Hardware path: self-service kiosk or interactive kiosk.
Window / walk-by promo (far)
Message length and physical letter size usually dominate over chasing maximum PPI. A lower-PPI larger image can outperform a dense small panel for the same walking glance. Run day and night checks when glass separates the viewer from the screen. Hardware path: window high-brightness display. Colour-range claims remain a separate brief — color gamut.
Hardware line by task
Select the product line that matches the task, then confirm that configuration’s documented diagonal and native resolution:
| Use case | Product / guide | How to use it here |
|---|---|---|
| Lobby / wayfinding standing screens | Floor-standing display | Mid / near info screens; PPI from documented size + native res only |
| Indoor network signage | Indoor digital signage | Indoor product-line entry |
| Self-service / touch | Self-service kiosk, interactive kiosk | Near-read + touch targets; PPI ≠ touch accuracy |
| Window / high ambient | Window high-brightness display | Far / glass; day and night acceptance |
| Multi-panel LCD walls | LCD video wall, how to choose an LCD video wall, bezel size | Density plus seams; select size model before content across joins |
| Side readability | LCD viewing angle guide | Separate from PPI |
| Colour range ≠ readability | Color gamut | Separate brief |
| Aspect / orientation templates | Display aspect ratio | Approve landscape and portrait separately |
| Drawings / manuals | Downloads | Confirm native resolution and install size |
FAQ
Does higher pixel density (PPI) always make digital signage easier to read?
No. PPI describes how many pixels fit into a physical length. Readability also requires physical letter size, viewing distance, contrast, hierarchy, and player scaling. A denser panel that keeps the same pixel-sized letters makes those letters physically smaller. Specify diagonal + native resolution, then test the smallest critical text from the real standing positions with the intended player output.
How do I calculate PPI, and what must appear with the number?
For square pixels: PPI = √(H² + V²) / diagonal_inches. A 55-inch 1920×1080 example is about 40.1 PPI; the same 55-inch at 3840×2160 is about 80.1 PPI. These are mathematical illustrations, not promises for a specific YJCEN SKU. On a quote, always pair diagonal + native W×H; confirm the selected configuration in Downloads.
What is the difference between PPI, pixel pitch, resolution, and readability?
Resolution = pixel count (W×H). PPI = pixels per inch at a stated size. Pixel pitch = spacing between pixel centres (often mm; with square pixels, pitch_mm ≈ 25.4 / PPI). Readability = whether people complete the reading / selection task from the intended positions. Do not treat any one figure as a substitute for the others. For multi-panel LCD seams, see LCD video wall bezel size.
Does a 4K panel guarantee that a menu or directory will be readable?
No. 4K only states pixel count. Check names, prices, and the longest normal strings from the customer’s position under representative lighting — including side approaches. Window jobs: day and night checks on the window high-brightness display path. A project case that lists 4K describes that install only.
Can one content file run on every screen size in a network?
A shared master can be convenient, but it is not automatic proof of readability. Validate each supported size and orientation. Where layouts differ, keep approved templates and publishing rules. Retest when columns, font sizes, or information hierarchy change — hardware PPI can stay unchanged while the new layout fails. Align portrait vs landscape framing with display aspect ratio.
Plan the screen and content together
Start with the farthest normal reading position and the smallest important message. Compare the actual layout at the proposed screen size, then choose the panel resolution and player output. A larger screen helps only when the layout gives the important text more physical space.
