Automate shooting pictures with different camera settings to find the ideal camera settings for your environment.

If you are using a canon camera that is supported by CHDK (http://mighty-hoernsche.de/) or SDM(http://stereo.jpn.org/eng/sdm/index.htm), you can determine ideal camera settings for your environment.  One of many features that CHDK (“temporary” firmware for certain canon cameras) provides is user defined scripts. 

I created a script to capture series of images with different camera settings. Each image will be taken using different

• Aperture
• Shutter speed
• ISO
• Light balance settings

My motivation for writing this script was to determine the ideal camera setting for my book scanner

After the script completes capturing all the images, it creates a text file that contains the image numbers and associated capture settings.  We can then simply evaluate them and make a selection accordingly.  To start:

1. You’ll need a build of CHDK running on your camera which can include CHDK (http://chdk.wikia.com/wiki/CHDK_for_Dummies)  or Microfunguy's Build (Stereo Data Maker http://stereo.jpn.org/eng/sdm/index.htm).   Here is a video instruction for installing Stereo Data Maker
2. You'll need to copy my CHDK script or SDM script (at the end of this document) to your camera’s SD-Card. It is probably best to copy it into /CHDK/SCRIPTS/ folder.
3. Enter you Camera’s Alternate mode.  This is typically done by pressing the print button.  When in Alternate mode, you will see ALT in the bottom of the screen.
4. Within ALT mode, press Menu button to activate SDM or CHDK menu.
5. Navigate to “Scripting…” and the click the “Set” button
6. Select load script from file
7. Scroll down to adjust preferred script parameters
   • Set display print counter (“Start Counter Indx”).  This number is intended to correspond to your image file number.  If your image captures start from 0001.jpg, then this value should be 1.  This image number will be printed and written into a file
   • Specify if you want to write the output to file (1=On,0=Off)
   • Set Aperture start and end range (“Aprt. Strt at” and “Aprt. End at”) where valid values range include: 9=F/2.7, 10=F/3.2, 11=F/3.5, 12=F/4.0, 13=F/4.5, 14=F/5.0, 15=F/5.6, 16=F/6.3, 17=F/7.1, 18=F/8.0
   • Set Shutter speed start and end range (“Shtr Spd Strt at” and “Shtr Spd End at”) where valid value range include: -12=15", -11=13", -10=10", -9=8", -8=6", -7=5", -6=4", -5=3"2, -4=2"5, -3=2", -2=1"6, -1=1"3, 0=1"", 1=0"8, 2=0"6, 3=0"5, 4=0"4, 5=0"3, 6=1/4, 7=1/5, 8=1/6, 9=1/8, 10=1/10, 11=1/13, 12=1/15, 13=1/20, 14=1/25, 15=1/30, 16=1/40, 17=1/50, 18=1/60, 19=1/80, 20=1/100, 21=1/125, 22=1/160, 23=1/200, 24=1/250, 25=1/320, 26=1/400, 27=1/500, 28=1/640, 29=1/800, 30=1/1000, 31=1/1250, 32=1/1600, 33=1/2000, 34=1/2500, 35=1/3200(s-series) .
   • Set the White balance start and end range (“WhtBlnc Strt a” and “WhtBlnc End at”) where valid value range include:  1=Day Light, 2=Cloudy, 3=Tungsten, 4=Fluorescent, 5=Fluorescent H
   • Set ISO setting ("ISO Strt at" and "ISO End at") where valid value range include: -1=HiIso, 0=AutoIso, 1=50(80), 2=100, 3=200, 4=400, 5=800
   • g. Set the delay between image Captures (“Sec Btwn Sht”) in 1/10 of a second increments.  For example to pause 3 seconds between every image capture, set this value to 30.
   • h. Specify number of pictures to capture per setting (“Sht per setting”)
8. Press the camera shutter button (shoot) one time to start the program. You should see:  “Clk remote btn 2 strt”
9. Click on camera “Set” button (“Remote” button for SDM) to start capturing sequence of images
10. When the script is done capturing images, it will beep three times.
11. Transfer images to your computer to evaluate
12. By comparing the images, identify the “best” picture and noting the image file number.
13. Open resulting print file for your camera.
    • Under Stereo Data Maker (SDM), open /CHDK/SCRIPTS/PR_SCREEN.TXT
    • Under CHDK, open /CHDK/LOGS/LOG_0001.txt
14. Find the desired image file number from step 12 in the above file.
15. Look at Aperture, ISO, White Balance, Shutter speeds immediately preceding the image number.

For example, say you found that the image 0260.JPG from step 12 is the best camera settings for your environment.  In the output file you should see something like:

Therefore, your camera setting to obtain image 0260.JPEG is:  Tungsten white balance, Apreture F/3.5, ISO 400, Shutter Speed 640
Note:  We used Apreture F/3.5 in step 191, instead of Apreture F/2.7 in step 51 because it was over-written; similarly, we used ISO 400 in step 248 instead of earlier ISO 50/80 in step 191.

That’s it.  Now you know the ideal camera setting for your environment.  Enjoy.

Attachments:

Find Camera Setting For CHDK	[CHDK Script for Finding Ideal Canon Camera Settings]	2 Kb
Find Camera Setting For Stereo Data Maker	[Stereo Data Maker (SDM) Script for Finding Ideal Canon Camera Settings]	2 Kb