Calling a tone-mapped phone photo an HDR file, when the wide range was compressed back into a standard image at capture.
Colour
HDR
Also called high dynamic range, hdr image or hdr photo. Here is what it means, when it changes what you export, and what people get wrong.
ColourRuns on your deviceUpdated 10 August 2026
The short answer
HDR means high dynamic range, a wider span between the darkest and brightest parts of an image than standard photography carries. The word covers two different things: a capture technique that squeezes a wide range into an ordinary file, and a delivery format that keeps the range for HDR displays.
Updated
The short version
HDR at a glance
| Quick fact | Detail |
|---|---|
| Two meanings | Tone-mapped capture, or true high range delivery |
| Transfer functions | PQ and HLG, not the sRGB curve |
| Minimum practical depth | 10 bits per channel |
| Formats that carry it | AVIF, HEIC, JPEG XL, PNG Third Edition |
| Not supported by | Baseline JPEG, without a gain map layer |
| Needs | Correct metadata, or it renders flat and grey |
Slide the table sideways to see every column.
Which HDR are people talking about?
Almost every argument about HDR comes from these two meanings being used interchangeably.
- HDR capture and tone mapping. Several exposures of the same scene are merged, then compressed back down so the result fits in a normal file. Your phone does this on every shot. The output is a standard image; the range was captured and then thrown away in a controlled fashion. This is where the flat, over-processed HDR look comes from.
- HDR display. The wide range is actually preserved and sent to a screen capable of showing it, using a transfer function built for high brightness, at least 10 bits per channel, and usually a wide colour gamut.
A tone-mapped photograph is not an HDR file. It is a standard dynamic range file that had a wide range as its raw material.
What makes a file genuinely HDR?
Three things together, and all three are needed.
- A high dynamic range transfer function. Usually PQ or HLG rather than the sRGB curve. These are defined for much brighter output, with PQ working in absolute brightness terms and HLG designed to remain watchable on standard displays.
- Enough bit depth. Ten bits per channel or more. At 8 bits, stretching over a wider brightness range puts visible bands in every gradient.
- A wide colour gamut. Typically Rec. 2020 or Display P3 primaries, so bright colours have somewhere to go.
The metadata matters as much as the pixels. Without a signal saying which transfer function and primaries apply, a viewer has no way to know it is holding HDR data and will render it wrongly, usually washed out and grey.
Which image formats can carry HDR?
AVIF is the most capable of the common web formats: it supports 10 and 12 bit depths and carries the colour signalling that HDR needs. HEIC, used by iPhones, also carries HDR. JPEG XL supports it. PNG gained official HDR support with the Third Edition, which became a W3C Recommendation in June 2025 and added the cICP chunk for exactly this signalling.
Baseline JPEG has no native HDR mechanism, which is why a newer approach stores an ordinary SDR image alongside a gain map that reconstructs the brighter version. Displays that cannot use it just show the normal photograph.
For marketplace listings, none of this helps yet. Platform pipelines re-encode uploads to standard formats, so the practical move is to convert HDR captures to an SDR sRGB JPEG or PNG yourself, using a converter such as Photomop's, rather than letting an unpredictable pipeline decide how to flatten them.
Why do HDR photos look wrong on some screens?
Two failure modes, and they look opposite. If the file's HDR signalling is missing or ignored, the values are read as if they were an ordinary sRGB image and the picture comes out flat, grey and low in contrast. If an HDR file plays on a screen that cannot reach the brightness it assumes, tone mapping in the display or operating system decides what to do, and the results vary from device to device.
There is also a social problem. An HDR image on a feed of SDR images can appear glaringly bright next to its neighbours, because it is using headroom the others are not. That is why some platforms cap or strip HDR on upload.
What people get wrong about hdr
Each one is a real failure mode, not a style preference.
Saving HDR data at 8 bits per channel, which bands every gradient because the range is stretched over too few levels.
Uploading HEIC HDR captures straight to a marketplace and letting an unknown pipeline decide how to flatten them.
Judging an HDR file on an SDR monitor and concluding the edit is wrong, when the display is simply tone mapping it.
Questions people ask
HDR, answered
The follow-up questions people search for once they have the definition.
Should I upload HDR photos to marketplaces?
No. Platform image pipelines re-encode uploads to standard formats, and how they flatten HDR is out of your control. Convert to an SDR sRGB JPEG or PNG yourself so you decide how the highlights land, then upload that.
Can PNG store HDR images?
Yes, since the PNG Specification Third Edition became a W3C Recommendation in June 2025. It adds the cICP chunk, which signals the transfer function and colour primaries an HDR image needs. PNG already supported 16 bits per channel, so the depth was never the limitation.
Why does my HDR photo look washed out on the web?
Because the HDR signalling was lost or ignored, so the viewer reads the values as ordinary sRGB. The bright range that should have been mapped to high output gets rendered at normal levels instead, which flattens contrast. Converting to SDR deliberately gives a better result than letting it be misread.
Is HDR the same as more megapixels?
No, they are unrelated. Megapixels measure how many pixels there are; HDR is about the range of brightness each pixel can represent. A 12 megapixel HDR image and a 50 megapixel SDR image differ on completely different axes.
Same cluster
More from the glossary
Neighbouring entries, so every term in the set is one hop from every other.
HEIC
HEIC is the format iPhones use for photos by default.
Halo (fringing)
A halo is the pale or coloured outline left around a cut-out when traces of the old background cling to the subject's edge.
Hero image
A hero image is the large lead visual at the top of a page, usually the first thing a visitor sees.
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Sources
Where the facts on this page come from. Every link opens the specification, standard or documentation the claim was read at.
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