How to use it
- Drop in .hdr files.
- Adjust the exposure: lower to recover bright skies, higher to lift shadows.
- Download the PNGs.
Why HDR files look wrong elsewhere
A Radiance HDR file stores light as real brightness values that can run far beyond what a screen can show: the sun in an outdoor HDRI can be thousands of times brighter than the shadows. Most image viewers either refuse the file or clip it, giving a blown-out white mess. To display it, the brightness range has to be compressed into the 0 to 255 of a normal image, which is called tone mapping.
How it is tone mapped here
Each pixel is scaled by the exposure you choose, then passed through a filmic curve, the widely used ACES approximation, which rolls off highlights gently the way film does, before sRGB encoding. The result looks natural at the default exposure for most HDRIs. Use the slider, in stops, to taste: each step of 1 doubles or halves the brightness.
Uses
Thumbnails for an HDRI library, previews for clients, reference images for lighting, or a backdrop in a presentation. For lighting in 3D software, always use the original HDR file; the PNG is a picture of it, not a replacement.
HDR and PNG compared
| HDR | PNG | |
|---|---|---|
| First released | Late 1980s | 1996 |
| Compression | RGBE with simple run-length encoding | Lossless |
| Transparency | No | Yes, including soft edges |
| Animation or pages | No | Only as APNG, rarely used |
| Best for | HDR lighting and environment maps | Screenshots, graphics, text and transparency |
| Support | 3D software; needs tone mapping to view | Universal |
Questions people ask
What exposure should I use?
Start at 0 and adjust by eye. Lower values recover bright skies; higher values open up interiors.
Can I use the PNG for lighting in 3D?
No. Lighting needs the full brightness range in the original HDR file.
Are EXR files supported?
Not yet. This converter reads Radiance .hdr (RGBE) files.