EXR vs PNG vs JPEG – which format for a 360° environment?

Use EXR when a 360° environment will light a 3D scene, PNG when it is only seen as a background, and JPEG when it has to travel over the web. The difference comes down to what each format can store. JPEG and standard PNG hold 8 bits per channel and stop at pure white, so a bright sun is recorded no brighter than a white wall. EXR stores light as floating-point numbers with no ceiling, so the sun stays far brighter than the sky around it, and that is what lets it cast convincing shadows.

Bit depth: how finely each format records colour

Bit depth is the number of steps a format can use for each colour channel. More steps means smoother gradients and more room to adjust the image before it breaks up.

Format	Per channel	Steps or range	Compression
JPEG	8-bit integer	256 steps, black to white	Lossy
PNG	8 or 16-bit integer	256 or 65,536 steps, black to white	Lossless
Radiance HDR (.hdr)	8 bits each for red, green and blue, plus a shared 8-bit exponent	Very wide range, modest precision	Simple lossless run-length
OpenEXR (.exr)	16-bit half float or 32-bit float	Values far above white, with fine precision	Lossless or lossy, several methods

For a 360° environment, 8 bits is usually enough to look at, because the image is shown much as it was made. The trouble starts when you change it. A smooth sky has very gentle gradients, and 256 steps spread across a large gradient leave visible bands, especially after exposure or colour adjustments stretch some of the steps apart. A 16-bit PNG has 256 times as many steps between the same black and white, so it survives grading far better. EXR goes further again, because floating point is not limited to a black-to-white scale at all.

Dynamic range: why lighting needs EXR

Dynamic range is the span between the darkest and brightest values an image can hold. In a real scene that span is enormous. The sun is many times brighter than the blue sky beside it, and the sky is brighter than the shaded side of a building. JPEG and PNG cannot record any of that above white: once a pixel reaches the maximum, it is simply white. The sun, bright cloud edges and a white wall all end up with the same value.

For a background you only look at, that does not matter much, because a screen cannot show anything brighter than white either. It matters as soon as the image becomes a light source. When a renderer or game engine lights a scene from an environment map, it adds up the light arriving from every direction. From a clipped 8-bit image, the sun contributes no more than a patch of pale sky of the same size, so the scene is lit evenly from everywhere, shadows go soft and weak, and nothing has a clear direction of light. From an EXR, the sun’s pixels carry their real weight, the light has a direction, and objects cast defined shadows.

EXR is also stored in linear light, where doubling a value means doubling the light. PNG and JPEG are usually stored in sRGB, which spaces the values to suit human vision and screens. Renderers do their lighting maths in linear light, so an EXR can go straight in, while an sRGB image has to be converted first. Engines do that conversion automatically when a texture is marked as sRGB colour, which is why the setting matters.

File sizes

Higher bit depth takes more space. Before compression, an 8192 × 4096 image with red, green and blue channels holds this much data:

Stored as	Bytes per pixel	8192 × 4096, before compression
8-bit RGB (JPEG, PNG)	3	96 MB
Radiance HDR	4	128 MB
16-bit RGB (PNG) or half float (EXR)	6	192 MB
32-bit float (EXR)	12	384 MB

Compression brings those numbers down, and by very different amounts. JPEG discards detail the eye is unlikely to miss and shrinks a 360° image to a small fraction of its raw size: the 4096 × 2048 JPEG worlds on this site weigh between about 0.4 and 2.6 MB. PNG and lossless EXR keep every value, so they shrink far less, and the result depends heavily on the scene, since smooth skies compress better than detailed ground. Half float is the usual choice for EXR environment maps: it keeps the full lighting range at half the size of 32-bit, and the extra precision of 32-bit rarely makes a visible difference to lighting.

Which tools support which format

Tool	JPEG and PNG	EXR	Radiance HDR
Unity	Yes	Yes, as an HDR texture	Yes
Unreal Engine	Yes	Imports as a flat 2D texture	Imports as a cubemap, ready for the HDRI Backdrop and Sky Light
Godot 4	Yes	Yes; the docs name .exr and .hdr for panorama skies	Yes
Blender	Yes	Yes, in the Environment Texture node	Yes
Web browsers	Yes, natively	Only through a JavaScript loader, such as the ones three.js ships	Only through a JavaScript loader

Unreal Engine is the one to watch. Its HDRI Backdrop and Sky Light want a cubemap, and Unreal builds one automatically from a 2:1 .hdr file, but an .exr panorama arrives as an ordinary 2D texture. Convert the EXR to .hdr first, for example by opening it in Blender and saving it as Radiance HDR. The Unreal Engine page covers the full setup.

Which format to choose

You are…	Use
Lighting a scene in Blender, V-Ray, Corona or Unreal Engine	EXR (converted to .hdr for Unreal’s HDRI Backdrop)
Setting a visible sky in a game with baked or its own lighting	PNG
Making a stylised game where the sky is part of the art, not a light source	PNG
Showing a world in a web viewer	JPEG, at high quality
Grading or editing the image heavily	EXR or 16-bit PNG
Sharing a preview or posting to social media	JPEG
Archiving the master copy	EXR, plus a PNG for quick viewing

Many projects use two formats for one world: EXR to light the scene and PNG or JPEG for what the camera sees. In Blender this is a two-node trick, explained in how to add an HDRI in Blender for world lighting. For architectural renders, where the sky has to light the building and fill the reflections in the glazing, the architectural visualisation page sets out the whole workflow.

Captured HDRIs and generated EXRs

It is worth being clear about what an EXR contains, because the format alone does not guarantee accurate light. A captured HDRI is made by photographing a real place at a range of exposures and merging them, so its brightest values are measurements of the real sun and sky. That is what physically accurate lighting studies need.

WorldGen360 Studio exports its worlds as linear floating-point EXR, alongside PNG in sRGB. The EXR drops straight into a lighting pipeline and gives a scene a sense of direction and mood from a place you described, but its light levels are the generator’s interpretation of that place, not a measurement. For concept work, look development, games and mood, that is exactly what you want. Where the numbers must be right, pair it with a sun light matched to the sky, or use a captured HDRI of a real location.

For how formats fit alongside projections and resolution, see the complete guide to 360-degree images, and for quick definitions of HDRI, HDR and EXR, the 360° glossary.

Frequently asked questions

Is EXR better than PNG?

For lighting, yes: EXR records light brighter than white, so the sun lights a scene properly. For a background that is only looked at, PNG is simpler, smaller and supported everywhere, and there is no visible advantage to EXR.

What is the difference between HDR and EXR files?

Both store high dynamic range. Radiance HDR packs each pixel into 32 bits, with a shared exponent for red, green and blue, which gives a wide range with modest precision. OpenEXR stores each channel as a half or full float, which is more precise, supports alpha and more channels, and offers better compression.

Can a web browser display an EXR?

Not on its own. Browsers show JPEG, PNG and WebP natively, but an EXR needs a JavaScript decoder, such as the loaders that come with three.js, and a tone-mapping step to fit its brightness onto the screen. For simply showing a world on a web page, use a high-quality JPEG.

Which format should I use for a Unity skybox?

EXR if the skybox also lights the scene through environment lighting and reflections, PNG if it is a visible backdrop only. The steps for both are in how to make a skybox in Unity.