I've just taken my first look at what the Adobe DNG converter
does when you give it a Pentax PEF file from the *ist-D
First and foremost: the DNG converter doesn't preserve all the
Pentax-private data from the MakerNote tag (including, amongst
other things, the code identifying the lens mounted on the camera).
I would strongly recommend any *ist-D owner save a copy of the
PEF file, even if you decide to use DNG as a raw file format.
THe release notes that come with the converter indicate that
Adobe is aware of this shortcoming, and may address the issue
in a future release.
So: how does the converter create the DNG file?
o Data copied from the PEF file
o The raw (12-bit) sensor data
o Most of the EXIF tags
Some of these values are copied over into EXIF data,
while some are copied into equivalent DNG tags. There
are also a couple of new EXIF tags which don't hold any
new data, but simply give the APEX-standardised format
for shutter speed and lens aperture.
o Data *NOT* copied from the PEF file
o All the JPEG images (thumbnails and full-size)
o The private settings from the MakerNote tag
o New data added to the DNG file
o A reduced-size (256 x 171) RGB TIFF image
o DNG-specific data
(I'm not sure whether some of this information
is taken from equivalent values in the MakerNote
tag, or whether it reflects best-guess settings
from Adobe. I'm inclined to suspect the latter)
o Sensor-to-RGB conversion matrices (for two
different, idintified, colour temperatures)
o Black level & White level
o Auto-White-Balance scaling factors
o Sensor crop region (offset & dimensions)
o Tags describing sensor layout, strength
of the anti-aliasing filter, etc.
o Data *NOT* found in the DNG file
o Linearization tables
This was a considerable surprise to me.
The DNG file format contains specifications for a
tag to describe the response curve of the sensor.
I expected to see this tag in the created file,
because both the Pentax Photo Laboratory and the
in-camera image processing algorithms appear to
use such a curve; it's probably the single largest
factor in explaining the different in appearance of
Pentax-created images as compared to those from any
other software.
Bottom line: this looks very much like a work in progress.
I'd expect to see a future release of the DNG converter
preserve more of the Pentax-specific information from the
MakerNote tag, and perhaps even use the same linearization
curve as the Pentax software. Until then I wouldn't use
DNG, even if I had any software that could read it.
