I'll try to write this without too many typos. I've looked at a couple of my
recent messages and found them full of mistakes.
I need more help and the quickest way to get it is to ask PDML.
1. Is the TIFF file output from the *ist D a real RAW file -- but with TIFF
format?
Just to (hopefully) clarify since some of my previous posts may
have confused.
TIFF is a rather general file format that can contain all sorts of
data. It can have different "tags" that can contain whatever data anyone
feels like putting there. Pentax (among others) have used the TIFF file
format to contain their RAW sensor data in their RAW files. In
Pentax's case this information is a simple, uncompressed bitmap that
contains the 12-bit linear data captured by the sensor. In the -D, the 12
bits is also padded with zeros to put it in a byte-friendly 16-bit size.
The common useage for TIFF files is to contain 8-bit,
gamma-corrected RGB data. They are what almost all people mean when they
say "tiff files". Within the context of RAW vs. TIFF files on a digital
camera, an image-type tiff file has had a number of processing stages done
to it over the RAW data:
- Bayer pattern interpolated to produce RGB image data
- White balance applied
- aRGB/sRGB colorspace transformation.
- Any in-camera image manipulation (saturation, sharpness, etc) performed.
- Nonlinear (gamma) correction.
- 8-bit truncated.
- Possibly losslessly compressed.
In fact, the *ONLY* difference between an in-camera TIFF file and
an in-camera JPEG file is that in addition to the above, a JPEG file has
been encoded with the JPEG DCT algorithm and has had further truncation
done.
Using in-camera tiff files in general is silly. It loses almost
as much information from the sensor as JPEG, but is between 1.5-2x the
size of the RAW file (8x3 bits as opposed to 12x1 or 16x1 for the -D).
-Cory
--
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
