JFIF defines a number of details that are left unspecified by the JPEG Part 1 standard (ISO/IEC 10918-1, ITU-T Recommendation T.81.
This pixel-producing information is rendered with the expectation of indicating rectangles by their centroid, rather than being pixel data directly, or being 'first corner and flood', etc.
JFIF provides resolution or aspect ratio information using an application segment extension to JPEG.
Exif images recorded by digital cameras generally do not include this segment, but typically comply in all other respects with the JFIF standard.
The JPEG standard used for the compression coding in JFIF files does not define which color encoding is to be used for images.
Moreover, CCIR 601 (before 2007) did not provide a precise definition of the RGB color primaries; it relied instead on the underlying practices of the television industry.
However, Photoshop generally saves CMYK buffers as four-component "Adobe JPEGs" that are not conformant with JFIF.
Since these files are not in a YCbCr color space, they are typically not decodable by Web browsers and other Internet software.
In practice, however, virtually all Internet software can decode any baseline JIF image that uses Y or YCbCr components, whether it is JFIF compliant or not.
As time went by, C-Cube was restructured (and eventually devolved into Harmonic, LSI Logic, Magnum Semiconductor, Avago Technologies, Broadcom, and GigOptix, GigPeak, etc), and lost interest in the document, and the specification had no official publisher until it was picked up by Ecma International and the ITU-T/ISO/IEC Joint Photographic Experts Group around 2009 to avoid it being lost to history and provide a way to formally cite it in standard publications and improve its editorial quality.