<!--
{
  "documentType" : "article",
  "framework" : "CoreVideo",
  "identifier" : "/documentation/CoreVideo/image-buffer-transfer-function-constants",
  "metadataVersion" : "0.1.0",
  "role" : "collectionGroup",
  "title" : "Image Buffer Transfer Function Constants"
}
-->

# Image Buffer Transfer Function Constants

Constants that indicate the transfer function for the image buffer.

## Discussion

Use the [`kCVImageBufferTransferFunctionKey`](/documentation/CoreVideo/kCVImageBufferTransferFunctionKey) key to attach one of these values to the image buffer. The transfer function describes the tonality of an image for use in color matching operations, along with a color primaries gamut (See [Image Buffer Color Primaries Constants](/documentation/CoreVideo/image-buffer-color-primaries-constants) for more information.). Most apps should specify the [`kCVImageBufferTransferFunction_ITU_R_709_2`](/documentation/CoreVideo/kCVImageBufferTransferFunction_ITU_R_709_2) transfer function.

## Topics

### Constants

[`kCVImageBufferTransferFunction_ITU_R_709_2`](/documentation/CoreVideo/kCVImageBufferTransferFunction_ITU_R_709_2)

A key to the transfer function for high-definition and standard-definition video.

[`kCVImageBufferTransferFunction_SMPTE_240M_1995`](/documentation/CoreVideo/kCVImageBufferTransferFunction_SMPTE_240M_1995)

A key to the transfer function for HDTV interim video.

[`kCVImageBufferTransferFunction_UseGamma`](/documentation/CoreVideo/kCVImageBufferTransferFunction_UseGamma)

A key to the transfer function that’s defined by the gamma level value of the image buffer.

[`kCVImageBufferTransferFunction_sRGB`](/documentation/CoreVideo/kCVImageBufferTransferFunction_sRGB)

[`kCVImageBufferTransferFunction_ITU_R_2020`](/documentation/CoreVideo/kCVImageBufferTransferFunction_ITU_R_2020)

[`kCVImageBufferTransferFunction_SMPTE_ST_428_1`](/documentation/CoreVideo/kCVImageBufferTransferFunction_SMPTE_ST_428_1)

[`kCVImageBufferTransferFunction_ITU_R_2100_HLG`](/documentation/CoreVideo/kCVImageBufferTransferFunction_ITU_R_2100_HLG)

[`kCVImageBufferTransferFunction_SMPTE_ST_2084_PQ`](/documentation/CoreVideo/kCVImageBufferTransferFunction_SMPTE_ST_2084_PQ)

[`kCVImageBufferTransferFunction_EBU_3213`](/documentation/CoreVideo/kCVImageBufferTransferFunction_EBU_3213)

A key to the transfer function that follows the EBU 3213 standard.

[`kCVImageBufferTransferFunction_SMPTE_C`](/documentation/CoreVideo/kCVImageBufferTransferFunction_SMPTE_C)

A key to the transfer function for standard-definition video.

[`kCVImageBufferLogTransferFunction_AppleLog2`](/documentation/CoreVideo/kCVImageBufferLogTransferFunction_AppleLog2)


---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)