EV Bracketing[]

Written for/on: Canon A640
Also works on: Other Canon AXXX (Not tested), A620 (tested), A590 (Camera settings: Menu->Review Off), A720 (tested ok)

EV Bracketing by Johan Van Barel (

The purpose is to create a High Dynamic Range (HDR) image from a set of images taken at different exposures.

The script takes a number of images around the selected EV setting. So if you take 3 pictures, with EV set to center and EV Step Size=3, it will take the first picture at -1EV, the second at Center EV and the third at +1EV. You can later stitch the images together with a program like Photomatix (

Canon A620[]

This script works well on Cannon A620, but you have to set the Script shoot delay setting to at least '4' and disable the Review function.

Documentation/Help (save as a small EVBracket.txt" file to your /CHDK/SCRIPTS/ folder)

Select P mode on your Canon A640


  • Number of Pics (Default=3)
  • EV Step Size (1/3 EV) (Default=3)
  • Initial Delay (Sec) (Default=1)

Script Code (save as "EVBracket.bas" to your /CHDK/SCRIPTS/ folder)

rem Johan Van Barel 07-07-2007
rem EV-Bracketing for Canon A640

@title EV Bracket (Select P Mode)
@param a Number of Pics
@default a 3
@param b EV Step Size (1/3 EV)
@default b 3
@param c Initial Delay (Sec)
@default c 1

if a<2 then let a=2
if b<1 then let b=1
if c<0 then let c=0

print "Pics:"; a, "Step:"; b

sleep c*1000

click "erase"
for n=1 to (a-1)*b/2
    click "left"
next n

print "Pic 1 of", a
for s=2 to a
    for n=1 to b
        click "right"
    next n
    print "Pic", s, "of", a
next s

for n=1 to ((a-1)*b+1)/2
    click "left"
next n
click "erase"