WhiteScreen Lab
Small, repeatable investigations into everyday screen uses. Every number on this page says whether it was calculated or measured.
- Calculated estimate
- From a mathematical model and the inputs you choose. Not a reading from any device.
- Physical measurement
- Taken with a light meter in a real room. Only these can confirm the model.
- Team field measurements
- None published yet. The calculator below is a model only.
01 · A screen as a light · model v1.0
How much light could your screen add?
Estimate the light reaching a point directly in front of a full-screen white page.
Ideal 14″ 16:9 screen at 400 nits · 31.0 × 17.4 cm
Drag along the curve, or use the distance field, to compare distances.
| Distance | Estimate | Relative to 40 cm |
|---|---|---|
| 20 cm | 360 lux | ×3.01 |
| 40 cm | 120 lux | ×1.00 |
| 60 cm | 57 lux | ×0.47 |
| 80 cm | 33 lux | ×0.27 |
| 100 cm | 21 lux | ×0.18 |
Model assumptions: an ideal, uniformly bright screen, centered and parallel to the receiving surface. Ambient light, automatic dimming, viewing-angle losses and changes of color are outside this model.
Physical measurements
No physical readings or before-and-after photos have been published by our team. Any measured results will appear here with their full method.
Measure it yourself
Use a light meter at the position you care about. Keep the room, screen position and meter orientation unchanged between readings.
- Record the screen model, meter, distance and system brightness. Disable automatic brightness and power-saving dimming; wait until the screen output has settled.
- Take an ambient reading with the light device switched off or its display fully covered. A black page can still emit light on an LCD.
- Show a fullscreen white screen and take the second reading at the same point, with the meter facing the screen. Subtract the ambient reading to estimate the added light.
- Repeat each pair at least three times and keep every reading. If taking comparison photographs, fix the camera exposure and white balance.
A screen’s advertised peak brightness may differ from sustained full-screen white. The calculation is an ideal reference; measurements need not match it. A meter with a documented calibration and suitable spectral response is needed for a publishable comparison.
Your measurement notebook
Your readings · unverifiedOptional. Keep your own readings and export them as CSV. Entries stay in this browser’s local storage and are not submitted to WhiteScreen.tv. They are your notes, separate from published Lab results.
Add a reading
| Screen / setup | Distance | Ambient | With screen | Added | Actions |
|---|
No readings saved in this browser yet.
Method and evidence
This page contains a mathematical model and a measurement protocol, not a completed device test. No physical readings or before-and-after photos have been published by our team yet. Entries in your notebook do not become public results.
How the calculation works
We derive the rectangle’s width and height from the diagonal and aspect ratio, then integrate illuminance over a uniformly luminous, Lambertian rectangle. The receiver is directly in front of its center and parallel to it. For luminance L in cd/m² and lengths in meters:
E = L ∬ d² / (d² + x² + y²)² dx dyThe integral covers the full screen rectangle; E is in lux. This accounts for the size of a nearby screen rather than treating it as a point light source. The model uses a closed-form evaluation of that integral. Nits mean cd/m²; a system brightness percentage cannot be substituted for luminance.
Background: Alex Ryer, Light Measurement Handbook: Basic Principles explains the point-source approximation and Lambert’s cosine law. The calculation and implementation here are ours.
What a published field test will include
Device and meter details, calibration information, sustained full-screen luminance when measured, distance and orientation, ambient conditions, all repeated readings, dated setup photographs, analysis and limitations. The operator and reviewer will be named when that work is completed.
Model and protocol by the WhiteScreen.tv team · November 2, 2026 · v1.0. Editorial standards · Corrections.