EV Bracketing Take a set of images at different exposures.


Introduction

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.

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


Parameters (Save as "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)

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

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

end