Canon CHDK Quick Start Manual page 41

• RAW Sum
Using the selected RAW files, this will combine them into one file. Working on an additive
principle. Meaning, if you take five 65-second exposures, then RAW Sum them together, the
resulting image will be equivalent to the brightness level of a 5 minute, 25 second exposure.
• RAW Average
This RAW Merge feature will, as it says, average all the frames together. Very convenient if
taking several identical frames at high ISOs at high shutter speeds. This will merge them
together, effectively obliterating any noise, as the noise gets averaged out. The more frames
used, the less noise visible.
• Purge RAW
< File Browser < Miscellaneous Stuff
With this function the RAW files can be deleted in 3 different ways...
Caution ! Erasing files in the camera is an irreversible operation !
Backup important images first, the data on your SD card may get damaged or
deleted !
The first step is to delete the JPG outtakes in playback mode (using Canon's
interface).
The 3 options for the Purge RAW function and erase the
corresponding RAW files:
1) Delete all RAW files in DCIM folder including
subfolders
Useful when:
You keep a separate folder for RAW files.
You set up the camera to create a new folder everyday
(several days trek, holidays etc).
You want to erase the occasional mischievous RAW file stored in a different folder.
Go to CHDK File Browser, select DCIM folder, push the left button to display the popup menu
and select "Purge RAW" (See image above). A warning will ask you to confirm (See image next
page) and voila! You have regained some SD space.
This feature will search through all the folders in DCIM looking for a RAW file (CRW/CR2
prefix or file extension) and if it finds one then will look for its JPG partner anywhere inside
DCIM (comparing the 4 digit number assigned by the camera). If it is not found, the RAW file is
erased.
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