Friday, October 11, 2013

Cameras for SfM

Camera choice for SfM is important...but maybe more important is taking the right photos. Taking the right photos is the subject of an upcoming post, but for now we'll just focus on cameras. I'll go over the setups we have running and also talk about some of the pitfalls of certain cameras.



We (the SfM group at the U of O) have several camera systems that we've built up over the last few years, ranging from $100 point and shoots to thousand dollar Digital SLRs. Our main camera lineup is exclusively Canon cameras, not because we get sponsored (although I wish we were), but because they are 'hackable'. These hacks are extra bits of software that run in the background to add extra functionality. The point and shoots can run CHDK and the DSLRs can run Magic Lantern. Both sites have a list of supported cameras.

Some considerations 

Here are a few things to consider before jumping off and finding the right balance

  • Resolution (the megapixels): Resolution is important, but there is a diminishing return on higher MP cameras. Also the megapixel specs are somewhat (or always) misleading, in that high MP number do not mean better pictures. For example, our Canon A3300 IS has a spec of 16MP and our SX230 HS has 12.1 MP. The SX230 HS takes far better photographs and works in a wider range of lighting conditions. Switching from a point and shoot up to and DSLR does improve picture quality noticeably (but I think we all knew that). Bottom Line: Picture quality is more important than the actual megapixels.
  • Portability and Durability: Where is the camera going? What kind of conditions is it going to be used in?...Point and shoots are great for quick SfM surveys and are easier to stow away if the weather turns. DSLRs are a bit more sensitive to moisture and take up more room in your pack. If the camera is going into real hostile territory, like rain forests or beaches, something fully waterproof/dust- proof would be good.

Camera Setups

Extra batteries and memory cards are important. We have a minimum of 3 batteries and 3 memory cards per camera. You can buy these from a lot of different places, Amazon, B&H Photo...but also check for refurbished models direct from Canon.
Point and Shoots
SX230 HS
  • SX230 HS (~$300) - This is one of our workhorse cameras. The batteries last a long time and it takes good pictures in a broad range of lighting conditions. It has an onboard GPS, but it's only accurate to 3-4 meters and it really drains the battery. The newer version of this is the SX 260 HS. Several colleagues have bought this one and been happy with it. To trigger this camera on our pole setup we use either the intervalometer built into CHDK, a wired shutter release, or a custom wireless release.


  • A3300IS (~$100) - A good little camera for quick SfM jobs / demos. Good for clear bright days. Triggering is same as the SX230.
A3300 IS
  • Waterproof Options - D10 and D20 - These are the only 'proof' cameras Canon offer. I would only go with these if you are headed into extreme conditions. They do an OK job on all fronts, but are a little limited.
    D20
D10

Digital SLRs
  • CANON T2i and T5i (~$1000) - We've opted for the lower end of the SLR spectrum, mainly because of cost. Both are outfitted with the 'kit' zoom lenses, the T2i has an 18-135mm and the T5i a 18-55mm lens. We almost always leave the lenses all the way out at 18mm, so a fixed prime lens at around 18 or 20mm would also work (they are just more expensive). We trigger these cameras with either an IR remote or a wireless shutter release. B&H has a good T5i bundle with lots of accessories.
T5i ready for takeoff on the helicopter.

Other Cameras
  • GoPro - GoPros are fun little cameras, but the lens distortion make them horrible for SfM.
  • Cell Phones - These can be good for quick demos, but I would not rely on them as a primary research camera.
  • Video - Video can be used for SfM, but the resolution is not ideal. A 1080 HD video is only equivalent to a 2 megapixel still (1920 x 1080 pixels). As an added complication, individual video frames are often blurry, so finding crisp video frames for SfM is difficult.

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