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# edrMetadata

Metadata describing the tone mapping to apply to the extended dynamic range (EDR) values in the layer.

```
var edrMetadata: CAEDRMetadata? { get set }
```

## Discussion

You must set this property before calling [`nextDrawable()`](/documentation/QuartzCore/CAMetalLayer/nextDrawable()).

The default value is `nil`, which means that the system doesn’t perform any tone mapping of data prior to passing it on to the display. Values above the maximum (<doc://com.apple.documentation/documentation/AppKit/NSScreen/maximumExtendedDynamicRangeColorComponentValue>) may be clipped.

If non-`nil`, the system uses the metadata provided to tone map values to the display, based on the display’s current characteristics. You must also set [`pixelFormat`](/documentation/QuartzCore/CAMetalLayer/pixelFormat) to a pixel format that supports pixel values greater than `1.0` (such as <doc://com.apple.documentation/documentation/Metal/MTLPixelFormat/rgba16Float>) and [`colorspace`](/documentation/QuartzCore/CAOpenGLLayer/colorspace) to a color space that supports a linear transfer function.

The tone mapping process requires significant amounts of memory and GPU processing.

---

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