Thursday, November 08, 2012

Mounting Cameras to view the Em2

Here's a helpful suggestion. Two really. Many of us with the Em-series stream tables, or other linear physical model often want to take time lapse photos of the stream table. To do this, you set up your camera and take a bunch of images in a sequence and then link the images together into a movie. I've also been using the X-Box Kinect sensor to make 3D scans of the Em2 - a setup that also requires a good, stable view of the stream table.

8-16Run01Kinect from Matt Kuchta on Vimeo.

7-16 Em2 run, 3D KinectData from Matt Kuchta on Vimeo.

How do you mount the camera so that it is both stable and oriented to get the best view?

First, you can use a tripod. In general this works rather well, but the camera is going to be elevated and looking down on the stream table at an angle, which is a particularly big problem with tripods that come with a fixed central column. This might look okay in a time lapse video, but is unacceptable for 3D scanning, since one edge of your picture is going to be very close to the scene and the other edge is going to be over 2m away from it.

Tripods with a repositionable central column are a much better option, since you can cantilever the center column out over the table and get closer to a top-down view, making the edges of the scene more equidistant. The resulting side-effect, though, is you lose subject distance and must go with a wider angle lens, introducing the potential for greater distortion. I use both a Gitzo carbon-fiber tripod and a Manfrotto aluminum tripod (something similar at B&H photo here) for time lapse work. I've also found it acceptable for the Kinect, since I don't need to be as far away from the stream table to keep the sensor within 1m of the subject. I went with a high-end carbon fiber tripod since I do a lot of hiking and nature photography, so if you're just doing studio work, it's overkill, but I am absolutely in love with my CF Gitzo 'pod. Links are to B&H items because their product search feature is the more customer friendly of the batch, but you can find similar items at Adorama, Hunts, Amazon, or at your local camera shop. The tripods they sell at places like Wal-Mart and Best Buy trend to the short, cheap and useless end of the product spectrum.

Here I've got the carbon fiber tripod holding the camera and the aluminum tripod holding the Kinect sensor. Both tripods are equipped with a ballhead - another handy item, since you get nearly full 3-axis movement for adjustments.

A second option, and one that I'm going to switch to, is using a C-stand (C for century). These things are a little bit more robust and their construction and design allows you to cantilever items much further out than the tripods center column. It'll need to be stabilized with some weights at its base, but I think the smaller footprint and further reach will quickly endear itself to this process.

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