Self-Capture Test
Screen Share Sharpness Tester
Your camera can look perfect while your slides, code, or spreadsheet text turn to mush for everyone else on the call. This shows a test pattern below, has you screen-share this tab back to itself, then measures exactly how much text sharpness and color detail actually survived the round trip.
Step 1
Test Pattern
This is what gets captured — don't resize the window once you start.
Step 2
Capture
Click below, then in the browser's share picker choose "This Tab" (Chrome/Edge) or this window (Firefox/Safari) — the one showing the pattern above.
Waiting to start.
Readout
Screen Share Sharpness Results
Text Sharpness Retention
- 8pt:—
- 10pt:—
- 12pt:—
- 14pt:—
- 18pt:—
- 24pt:—
Color Detail
- Luma (brightness) Retention:—
- Chroma (color) Retention:—
- Subsampling Verdict:—
If color detail retention is meaningfully lower than brightness retention, that's a real signal your capture pipeline is smoothing color more than luminance — a classic sign of chroma subsampling somewhere in the chain.
Notes
Why shared screens go blurry when your camera looks fine
A camera feed and a shared screen are encoded very differently, which is why one can look perfectly acceptable while the other turns to mush. Video codecs are tuned for natural images — faces, movement, gradual gradients. They handle a shared screen badly, because a screen is full of exactly what codecs discard first: hard edges, fine text, single-pixel lines, and large areas of flat colour interrupted by sharp detail.
Compounding this, most platforms allocate less bandwidth to a shared screen than people expect, and many reduce colour resolution more aggressively than brightness resolution. That is the specific reason coloured text on a coloured background often becomes unreadable while black text on white survives.
What the two retention figures mean
Luma retention measures how much brightness detail survives the round trip. This governs whether ordinary dark-on-light text stays crisp.
Chroma retention measures how much colour detail survives. When this sits well below luma retention, your pipeline is subsampling colour — a standard compression technique that is nearly invisible on faces and very visible on coloured text, syntax-highlighted code, and charts with adjacent colour blocks.
The gap between the two numbers matters more than either alone. A large gap tells you specifically to avoid relying on colour to convey meaning in anything you present.
Presenting so it survives compression
Benchmark Reference
Reading Retention Percentages
| Retention | What it means |
|---|---|
| 85% – 100% | Edge detail essentially fully preserved — safe to use. |
| 60% – 84% | Noticeably softened but likely still legible at normal viewing distance. |
| Under 60% | Significant detail loss — treat this size or style as unreliable for presenting. |
Each row of the test pattern is measured independently, so you can see exactly which text sizes and colour combinations hold up and which don't.
Step-by-Step
How to Run the Test
- Start a screen share in your conferencing app of choice, sharing this browser tab or window.
- Have someone else — or a second device — capture what they actually receive and click "Capture" on that view.
- Read the per-row retention percentages for each text size, plus the overall luma/chroma retention and subsampling verdict.
- Repeat with a different platform or share mode to compare how each one handles fine detail.
Common Questions