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CHDK: Programming Photography

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It is easy to get frustrated with affordable point-and-shoot cameras that lack manual controls. It can get even more frustrating when one has to hack together electronics and web-cams to do things like time-lapse photography. I have found a inexpensive way to combine my love of programming with my photographic hobby.

CHDK, the Canon Hack Development Kit -- is a non-destructive open source firmware upgrade for some Canon P&S cameras. CHDK opens most of the controllable elements of the camera up to pre-selectable override values or to script control. Allowing you the programmer/artist to take control of your camera the way a programmer wants to.

I purchased a cheap Canon camera on ebay and loaded CHDK and now I have an incredible platform for less than 80$!

What are some of the things that CHDK lets you do?

RAW Images -- the sensor data before it has been processed and compressed into the final JPEG. Although not quite as exciting as I initially thought (for example the image data is still compressed but far less than the final product) these images generally allow for manipulations that are not possible in the final images.

Manual Controls -- I can set the shutter speed (more about this later), the aperture (actually only an ND filter on my camera), the ISO, and the focus.

Bracketing -- the ability to change values for the manual controls to bracket shots.

USB triggering -- They found a neat little trick on the USB interface allowing you to build USB remote "button" which can be used in scripts.

Motion Detection -- Snap a picture when something in your frame moves form one cell to another. This has been used to capture pictures of lightning!

Since you can "lock" settings you can use multiple exposure techniques for image stacking. You can enhance detail/remove noise/grain, do HDR shots, and do focus stacking.

The most interesting feature to me is the ability to set very high shutter speeds. This allows you to do high speed photography in natural light (i.e. without *requiring* a flash -- however I find that it is actually pretty hard to get enough light for really high speed shots so the flash sync helps).

Here are some images I took with my cheap little ebay camera:

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This first one was taken with a flash and continuous shots of my bathroom faucet dripping. I thought you needed a laser trigger but honestly just putting the camera on continuous and hope for the best works pretty well. I did this at 1/50000 of a second. Overkill I know but I was having trouble catching a droplet. Turns out you have to really turn up the stream to increase your chance of catching a droplet.

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Although you don't need a flash, this photo was taken in sunlight, the high shutter speeds really do require a LOT of light. The 70's like coloring is caused by white balancing an underexposed image. This was at a much lower shutter speed so there is a little bit of motion blur which is covered up nicely by the high-iso grain.

I have plans for some time-lapse animations, I am excited to use HDR and I have ALWAYS wished I could just do image stacking to help cleanup the noise. So as a programmer I am very excited by this project. I just wish there was a NHDK for my Nikon too!

5 Comments On This Entry

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05 April 2011 - 03:12 AM
I really enjoyed this blog post. :)

Shane Hudson 

05 April 2011 - 01:02 PM
Blimey, I cannot take photos that good with my not-so-cheap Canon 20D!


05 April 2011 - 03:41 PM
Well the first one sure you can but it is not easy. It requires some kind of trigger for falling objects it is typically a laser but I think a sound trigger might work as well. Anyway you get the room completely dark. Open your shutter and trigger a flash. Tada! But CHDK is MUCH easier!


05 April 2011 - 05:45 PM
Wow! Those pictures are amazing!


05 April 2011 - 09:14 PM
Thank you. I keep trying to think of things that I can take high speed pictures of. I think I may try popping water balloons but not until I can rig some kind of trigger because these were hard enough to capture.
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