Thursday, May 29, 2014

Using an action camera for model railroad video

By now I made several longer and shorter videos filming model railroad scenes from a moving train using my Sony HDR-AS15 camera. Here's an overview of the things I've learned while doing that.

Sony HDR-AS15 on the Welztalbahn
The AS15 has built-in WiFi providing it's own access point. This makes it very easy to control the camera remotely from an Android phone. The official Sony software for Android with the imaginative name "Sony PlayMemories Mobile" is quite clunky and buggy. However, it's ok for getting the point of view, starting and stopping recording. The software likes to randomly drop the connection between camera and phone. If that happens while recording, the camera just keeps going and upon reconnect the app gets the current state and video stream from the camera. I haven't had a case yet where a connection drop affected the recorded video. The camera records in HD 1080p and produces MP4/H.264 files. While the software supports wireless downloads, and the camera shows up as a storage device when connected to USB, I usually just pop the micro-SD card out of the camera and load the files directly to disk for editing and post-processing.

The HDR-AS15 (and it's non-Wifi enabled sister HDR-AS10) has a great form factor for model railroad video in HO or larger. The lens is on the end of the camera not the front like most other action cameras, so its profile naturally lends itself to be put on a flatcar and pass through tunnels just fine. The camera has no orientation sensor, so video recorded with the camera on its head needs to be flipped during video editing.

Scratch-built camera cradle
Since the camera looks like a symmetric flattened tube, it needs some support to stay in place and not tip over. I built a cradle from styrene. Originally, I built it so that it would fit perfectly in one of my gondolas, but it turns out that due to the thickness of the molded body the total contraption became too high to pass through the tightest places inside my tunnels. I resolved this by mounting the cradle to the metal underbody of an older kit-built car. Lowering the camera this way just barely cleared the tightest spot inside Hochwaldtunnel. You can hear the pantograph guide inside the tunnel scratching the camera case at 0:44 during the cab-ride across the Welztalbahn.

I cover camera orientation and point of view in a follow-up post.

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