Photoshop Transfer Function
From Just Solve the File Format Problem
Photoshop Transfer Function is a Photoshop format that stores a transfer function, i.e. a way to adjust the brightness, contrast, etc. of an image.
It is distinct from Photoshop Curve format, though the formats appear to be used for roughly the same purposes.
Identification
According to the documentation, a Transfer Function file begins with bytes 00 04
, and is exactly 114 bytes in size.