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Scientific Time Lapse System

Posted: Fri Jun 01, 2012 6:06 pm
by pld7
I'm trying to use the RPi to create a system that allows me to take a time-lapse series of a plant while it grows (I ultimately want to be able to capture images from multiple cameras of many plants growing in the dark using an array of infra-red cameras). I have a sketchy plan of how I'm going to do it which I thought I'd post here in case anyone had any ideas or experience doing what I'm trying to do.

My reason for using the RPi is because I want this project to be cheap enough that schools can use my apparatus so, using expensive cameras is not an option. I want to use webcams for the imaging.

My plan is to use Open Computer Vision (OCV) running on an Arch Linux RPi. At the moment I plan to write any programmes I need in Python but this choice is somewhat uninformed so if there's a better language, I'm all ears.

I'm assuming OCV will give me all the control I need over the webcams I'm using (I have a bunch of webcams and I'm not sure which one will work best). A problem I've run into using webcams with 'Cheese' is that they auto-adjust things like gain which means the images created are not homogeneous enough for time lapse. OCV seems to allow you to control this but I have no experience with it so any advice would be helpful.

I realise this is a bit meandering so, to summarise, my main questions are.

1) Will OCV give me enough control over relatively cheap webcams to produce a time-lapse stack that's usable?
2) Will I be able to create a program in Python that takes time lapse images (I'm sure I will) and do you have any ideas about how I might go about creating this? (I'm a novice at programming but I have some more experienced people helping me)
3) Do people have any general advice about setting up Arch on RPi, or setting up OCV on Arch?

Re: Scientific Time Lapse System

Posted: Sun Jun 03, 2012 3:14 pm
by roblham
Are you aware of CHDK? It's hacked firmware that runs on Canon compact cameras without voiding the warranty and enables features like manual mode, timelapse, motion detection and RAW files. It might be a better solution for you.

For under 150 GBP you could buy a Canon A800 camera, memory card, AC adaptor and little tripod, set it all up and let it run. The quality will be vastly superior to what a webcam can produce and you have the option of using flash in the pitch black. The most expensive part is the AC adaptor so if you could DIY that you could perhaps get the price under 100 GBP.

I know this is more than you'd pay for the Raspberry Pi but not vastly. Keyboard, USB power, mouse and HDMI cable cost an average of about 5 GBP each plus SD card and webcam at about 10 GBP each and the Pi at 29 GBP comes to a total of around 70 GBP.

Interestingly, Canon cameras run on customised ARM chips like the Raspberry Pi.

Let us know how you get on.

Re: Scientific Time Lapse System

Posted: Mon Jun 04, 2012 3:46 pm
by pld7
roblham wrote:Are you aware of CHDK? It's hacked firmware that runs on Canon compact cameras without voiding the warranty and enables features like manual mode, timelapse, motion detection and RAW files. It might be a better solution for you.
I didn't know about this. It's a very interesting idea. The only problem is that for the purpose of the experiment using even a very short flash would have the potential to change the outcome. I know that digital cameras detect a slightly broader spectrum than the human eye so it may be possible to use some IR LEDs to illuminate the plants. I'll look into it.