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•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 subfoldersUseful 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.