I was wondering if anybody knows of any software for a computer that would use a webcam to monitor an area and tigger a DSLR to take a picture when motion is detected?

I'm using a Canon T2i and a windows 8 computer.

  • \$\begingroup\$ Is your aim to reduce battery drain of your system camera by using the webcam for monitoring and triggering? \$\endgroup\$ Commented Aug 19, 2013 at 15:14
  • \$\begingroup\$ my am was to have the camera attached to the computer so space isn't an issue for the pictures being taken. i have an AC Adapter for the camera so power isn't an issue. \$\endgroup\$
    – thebtm
    Commented Aug 19, 2013 at 17:02
  • \$\begingroup\$ I'm not sure how tethering works in combination with Magic Lantern. According to this forum topic it should be possible. As it's free you could try it out yourself and report back here for future users. \$\endgroup\$ Commented Aug 19, 2013 at 17:56
  • \$\begingroup\$ I will take a look over it. thank you very much. i'll report back what i find. \$\endgroup\$
    – thebtm
    Commented Aug 27, 2013 at 3:19

4 Answers 4


While this solution does not use a webcam, it does what you want.

The Magic Lantern custom firmware can be downloaded for free and includes, among many other interesting features, motion detection functionality.
The firmware is not installed on the camera but on the memory card. If you don't like it, just format the memory card.

It supports a wide range of Canon cameras, including the Canon T2i/550D.

  • \$\begingroup\$ An explanation of the downvoter would be helpful such that I would know how to improve my answer. \$\endgroup\$ Commented Aug 22, 2013 at 22:24

You can attach any UVC-compliant web cam to a Linux computer (including a Raspberry Pi) and use the excellent Motion package to do the motion detection. It has the option to run a command when it sees motion, and you can set it up to call GPhoto2 and take a picture with your attached T2i.

  • \$\begingroup\$ i'll give this a try. I'll setup a linux VM on my desktop. \$\endgroup\$
    – thebtm
    Commented Jan 16, 2014 at 20:09
  • \$\begingroup\$ Also I should have mentioned, if you're only interested in simple motion triggering rather than using a webcam in particular, you can build a very simple circuit using a PIR motion sensor link that triggers the camera directly using its remote shutter port. Let me know if you would like the full details, all the parts together are ~$15, possibly less than a web cam. (I actually just built one of these for my dad). \$\endgroup\$
    – ARM
    Commented Jan 16, 2014 at 20:59

The CameraAxe will let you trigger your camera from nearly anything, sound, light, lightening, movement, etc. Its available as a kit or completed.



While not using a webcam per se, the CHDK = Canon Hack Development Kit could be used for your task with relative ease.

On cameras which it works with, CHDK allows flexible control of all camera features.
CHDK will not run on the t2i directly, but it can be used on many Canon 'point and shoots'. As you have control of USB functions and other features a means should be able to be found to use a cheap Canon point & shoot as a trigger source in the same way that you suggest with a webcam. Later camera models may not work but extensive details and compatibility lists are available. CHDK loads on an SD card which is read by the camera at powerup and used to temporarily load the program to camera memory. The load is transient, being limited to the current power-up session and causes no permanent camera changes.

CHDK can control just about any camera controllable feature and can output data on the USB port. This could be used with relatively simple hardware for camera control. CHDK allows eg defining a window within its view area and capturing images or performing other functions when motion is detected.


IEEE Spectrum writeup 2010

Lifehacker - good review and overview 2009


  • Note that CHDK will run on a Canon 400D directly.

Using a CHDK equipped camera to trigger a DSLR flash:

There are many possible ways. Here are two -

(1) Use remote flash sensing trigger module on DSLR -

  • these are available at low cost for all DSLRs

Trigger flash on CHDK camera to optically trigger DSLRs.

Can be arranged if desired so that CHDK camera flash does not illuminate main target.

(2) Obtain optocoupler requiring a few mA input current, bipolar or MOSFET transistor output. (1-5 mA best, 5-10 mA should be OK, much gigherworks but unneeded.

Place opto coupler input + resistor to suit desired current from USB+ to gnd on CHDK camera USB connection.

On motion detection, trigger initiate CHDK camera USB action - can be anything that toggles USB+. For opposite "sense" use USB- to ground.

Use opto output in any of the circuits available on web for camera triggering via external trigger socket. There are many and nominating any one is pointless. Opto ouput acts as a single pole single throw switch.

  • 2
    \$\begingroup\$ CHDK is not available for the Canon t2i. Maybe you're confusing the T2i with the 400D? The T2i is actually the Canon 550D. \$\endgroup\$ Commented Aug 19, 2013 at 14:40
  • \$\begingroup\$ @BartArondson No confusion. I noted that CHDK ran on the 400D BUT I was mainly pointing out that CHDK ran on many Canon 'point and shoots'. As you have control of USB functions and other features a means should be able to be found to use a cheap Canon point & shoot as a trigger source in the same way that he suggested using a webcam. I thought that woul;d be obvious from what I said but apparently the downvoter at least did not realise. a \$\endgroup\$ Commented Aug 20, 2013 at 16:28
  • \$\begingroup\$ I down-voted it as the OP asked explicitly for a solution using his 550D based on the misunderstanding that you suggested CHDK for the 550D. But now I understand that you meant to use the CHDK for the "trigger" camera. However, how does the OP connect his DSLR such that the point&shoot is able to trigger it? That's not really trivial and you only mention it shortly in your answer (`with simple hardware for camera control). As this still doesn't answer the question completely I won't remove the down-vote. \$\endgroup\$ Commented Aug 20, 2013 at 17:09
  • \$\begingroup\$ @BartArondson There are too many possible answer to how to do it with simple hardware as CHDK is flexible in capability. As there is a vast number of people who seem to be able to work out how to use eg Arduino's to do real world things (to my amazement and joy) I'm confident that thebtm or a friend can close the gap. eg if you can make CHDK wave a USB signal line it is easily detected. One 10 cent (if that) transistor adds a flash trigger. If you can fire a flash or step change the supply current or ... it will suffice. \$\endgroup\$ Commented Aug 20, 2013 at 23:21
  • \$\begingroup\$ @BartArondson I personally share Ret Butlers last recorded position re downvotes BUT am sad when they may discourage seekers from looking at an answer which actually DOES meet the voting requirement but somebody has decided to apply their own rules and mislead people. The answer IS useful (even if not used) and somebody looking at answers subsequently may be pleased to apply it. || Magic Lantern is probably a better & easier solution in this case, as you suggest. \$\endgroup\$ Commented Aug 20, 2013 at 23:24

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