How an image can render brighter than your screen's white
2026-07-14 · ~8 min read · Image Tools · Marketing
You may have seen LinkedIn posts where a logo seems to glow — visibly brighter than the white feed chrome around it. It looks like it breaks the rules of the screen. It doesn't. It exploits a real gap between what "white" means in standard dynamic range (SDR) and what modern HDR displays can physically output.
Try it yourself: Open the free HDR Glow tool — runs in your browser, nothing uploaded, batch ZIP supported.
SDR white is not your display's maximum
A normal sRGB image tops out at code value 255 — "white." Your operating system maps that to a comfortable reference level, roughly 200 nits on many laptops. But an HDR-capable panel (recent MacBook Pro, iPhone, Pixel, most OLED TVs) can output 1,000–1,600 nits in highlight headroom. Apple calls its implementation EDR (Extended Dynamic Range). Regular UI and SDR photos never touch that headroom — only HDR video and photos tagged as HDR content do.
The trick for still images is convincing a color-managed renderer that your JPEG is HDR content, even though it is an ordinary 8-bit file.
The signal: Rec.2100 PQ in an ICC profile
HDR video signals brightness using the PQ (Perceptual Quantizer) transfer function from ITU-R BT.2100 / SMPTE ST 2084. Unlike sRGB's relative curve, PQ maps each code value to an absolute luminance, up to a theoretical 10,000 nits.
ICC color profiles can describe a PQ encoding. When you embed a Rec.2100 PQ profile into a baseline JPEG, color-managed renderers — Chrome, Safari, macOS, iOS — honor it and render bright values into the display's spare brightness. White in the image can land at 1,000+ nits while the page's CSS #ffffff sits at ~200. The image out-glows the interface.
Credit where due: the PQ-profile technique and the finding that it survives LinkedIn's JPEG pipeline were first documented by Tom Nick. Tools like our HDR Glow encoder add luminance masking so only highlights glow while colors stay pinned near SDR reference (~203 nits).
The pipeline (what happens per pixel)
- Decode sRGB to linear light
- Convert primaries from sRGB to Rec.2020 with a 3×3 matrix
- Mask whiteness: non-white pixels stay at ~203 nits so hues don't shift
- Boost masked white regions toward your chosen peak (e.g. 1000 nits)
- PQ encode to 8-bit values
- Write JPEG via canvas, then splice the ICC profile into an APP2 segment after the SOI marker (
FF E2 … "ICC_PROFILE\0")
Canvas toBlob alone cannot embed ICC profiles — the profile is byte-spliced after encode. That is why this is a small amount of image science, not just a filter.
Platform survival matrix
| Channel | Survives? | Notes |
|---|---|---|
| LinkedIn feed (direct JPEG upload) | Usually yes | Don't crop in composer |
| Variable | Re-encoding may tone-map | |
| Screenshots | No | Captures tone-mapped SDR result |
| WhatsApp / iMessage | No | Heavy recompression |
| Email inline | Rarely | Clients strip metadata |
Who actually sees the glow?
Only viewers on HDR displays in color-managed apps, with battery saver off. Everyone else sees a normal JPEG with slightly dimmer whites. That is expected — you are not breaking physics on SDR panels, you are opting into headroom where it exists.
Honest caveats
This is attention arbitrage on borrowed time. Platforms clamped auto-HDR video brightness after similar tricks flooded Reels and Shorts; still images may follow. Use taste: a subtle glow on a wordmark reads as craft; a 4,000-nit full-frame flashbang reads as spam.
8-bit PQ encoding banding shows on smooth photo gradients — logos and flat graphics work best. For platform sizing before glow, use our Social Image Resizer or Image Resizer. To shrink file weight after export, try the Image Compressor — but re-compression may affect ICC survival depending on settings.
Related tools
- HDR Glow Image Encoder — create PQ ICC JPEGs in your browser
- Social Image Resizer — LinkedIn, Instagram, X dimensions
- Image Format Converter — PNG/JPEG/WebP/HEIC
- Image Tools hub