A few File standards¶
Here is a list of some standards associated with common files.
Not all technical possibilities for each type of file are listed here, only the most common (and most standard) are indicated.
It should be noted that you can use any color space with any format, but most don’t record the information in their metadata, and not respecting these proposed standards therefore requires changing the interpretation each time the resulting file is imported and used.
While these lists aren’t necessarily official standards, these correspondences are standardized by usage.
Image formats (Jpeg, PNG, TGA, TIFF…)¶
- Space : sRGB
- Pixel format : RGB, Full Range, , YUV in some (e.g. Jpeg)
- Depth :
- Jpeg : 8 bpc
- PNG : 8 bpc, 16 bpc
- TGA : 8 bpc
- TIFF : 8 bpc, 16 bpc1
Hint
It’s possible to see PNG HDR which use the color space Rec.2020.
OpenEXR¶
- Space: Linear RGB, but it’s also the official format for ACES, or Blender Filmic or Agx. It’s the only format that actually allows any existing color to be stored independently of the color space used to represent it, and therefore the preferred format to work with.
- Pixel format :
- RGB, Full Range
- YUV 4:4:4 or equivalent to YUV 4:2:0 with Luma/Chroma option, Full Range
- Depth :
- 8 bpc
- 16 bpc (integer or float)
- 32 bpc (integer or float)
Hint
The whole point of EXR is that it can store colors in a floating point format instead of the usual integers; it’s therefore useless to use the integer versions of the depth. It’s thanks to this floating point format that the EXR can losslessly store any color data.
Note
It should actually be understood that the color space in an EXR file doesn’t matter: the file stores raw data, which isn’t “clamped” (values above 1, the theoretical maximum of a color space, are possible); an EXR file can therefore store colors outside the gamut* and of the luminosity* of its color space.
MP4 h.264 / h.265 / AVCHD / HEVC and other HD (2K) or UHD videos (4K)¶
- Space : Rec.709, Rec.2020 possible in UHD and more (4K), or Rec.2100 PQ or HLG with High Dynamic Range.
- Pixel format : YUV 4:2:0 ; although 4:2:2 and 4:4:4, or even RGB, are possible, they’re not very standard and many players will not be able to read them. Limited Range
- Depth :
- 8 bits in Rec.709
- 10 bits in Rec.2020 UHD/4K
- 12 bits in Rec.2020 4K HDR
SWF (and others web formats)¶
- Space : sRGB
- Pixel formats : RGB, Full Range
- Depth : 8 bpc
Be careful, Adobe After Effects (at least some versions), imports it in Rec.709 instead of sRGB. It’s then necessary to change the interpretation manually.
QuickTime Animation / RLE¶
- Space: Rec.709
- Pixel format : YUV 4:4:4, Full Range
- Depth : 8 bpc
Apple ProRes¶
- Space: Rec.709 or Rec.2020
- Pixel format : YUV 4:2:2 or YUV 4:4:4. In 4:4:4 it is possible to add an alpha channel.
- Depth:
- 10 bits in 4:2:2
- 10 bits or 12 bits in 4:4:4
Avid DNxHD¶
DNxHD is dedicated to resolutions up to 1080 pixels in height. For higher resolutions, see Avid DNxHR.
The different standard formats in DNxHD are given by the value of their compression rate in Megabits per second.
- Space: Rec.709
- Pixel format:
- YUV 4:2:2 for bitrates lower than 300 Mbps
- YUV 4:4:4 for bitrates higher than 300 Mbps
- Depth:
- 8 bits
- 10 bits for bitrates labelled “x” (e.g. “220x”)
Avid DNxHR¶
DNxHR is the successor to DNxHD for very high resolutions.
- Space: Rec.709 or Rec. 2020
- Pixel format:
- YUV 4:2:2 for the LB, SQ, HQ and HQX versions
- YUV 4:4:4 for the 444 version
- Depth:
- 8 bits for the LB, SQ and HQ versions
- 12 bits for the HQX and 444 versions
-
TIFF allows many different color spaces, including CMYK and CIE Lab for example, and also the YUV format in a less standard way. ↩