Processing Raw Images - Canon Camera Hackers Manual

Prefixes and Suffixes
Tools such as DNG4PS-2 (section 4.5.4) and ZoRa Photo Director can auto-
matically pick the EXIF data from a corresponding JPEG file when process-
ing RAW images—provided that the image name starts with the prefix
IMG_ and that both the JPEG and RAW files are stored in the same folder.
You should enable the option RAW File in Dir with JPEG and set the param-
eter RAW File Prefix to IMG_ in order to make use of these tools.
The CHDK allows you to select different file name extensions for RAW
files. The purpose of this is to trick image uploaders that are not designed
to upload RAW images into uploading RAW files. However, if your image
uploader can handle the CRW file extension, or if you work with a card
reader, you should definitely use the CRW extension.
Similarly, you should use the extension DNG when you use DNG as your
output format. Enable the option 'DNG' file extension.

4.5.4 Processing RAW images

Many photo editors such as Photoshop, Paint Shop Pro, Picture Window, and
so on can import RAW images. And then there are the specialized, work-
flow-oriented RAW developers such as Aperture, Lightroom, CaptureOne,
Helicon Filter, BreezeBrowser, SilkyPix, DxO, RawTherapee, and others. These
programs have highly specialized tools for developing RAW images. Many
lens and sensor imperfections—such as chromatic aberration, pincushion
distortion, vignetting, sensor noise, and dead or hot pixels—can be cor-
rected. You will be surprised by the quality you can get from the lens of your
compact camera.
Unfortunately, not all of the above programs are happy with the RAW
format produced by the CHDK. One notable exception is the free RAW de-
veloper RawTherapee, which does an excellent job of converting CRW files
into TIFFs or JPEGs.
Your other option is to use the DNG format as RAW format (section
4.5.2). Alternatively, you can do the conversion from RAW to DNG on a PC
with the help of the free program DNG4PS-2.
You may very well ask, which is better: to conveniently create the DNG
file in-camera, or to shoot in native RAW format and let DNG4PS-2 convert
the images to DNG? The results are actually quite similar. This makes sense,
since RAW-to-DNG conversion never modifies the sensor data but only re-
packages it. The only exceptions are the bad pixels. When creating the DNG
file in camera, bad pixels can be removed (section 4.5.2). This is not the case
when you create a CRW file and convert it to DNG with DNG4PS.
4.5 Shooting RAW
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