Originally posted by Tan68 I don't quite follow why the PS image can not be saved as a PEF.
Multi-exposure sets are 'flattened' to one raw image so why not the 4 raw files incorporated into the PS image. A regular raw image contains interpolated color infos and the PS raw has more accurate color infos. It should be possible to record the more accurate information and export as raw..
A regular raw, or a "flattened" multi-exposure raw still only contains one (14bit) value per pixel, for instance the value for red, the other two colors blue and green has to be estimated from the surrounding pixels by the raw converter.
That is where PS comes in and records all three (red, green and blue) values for every pixel, and thus it can't be "flatened" to a normal raw which only contains one value per pixel.
A normal tiff however does hold three values per pixel but comes in different sizes, three 8bit values per pixel or three 16 bit per pixel and since the camera records 3x14bit per pixel in PS mode they should use the 16bit version or data will be thrown away. Apparently the camera only produce 8 bit tiff while DCU can produce 16bit tiffs which are a lot more suitable for editing since it holds all the data originally captured by the camera.