As a camera agnostic software solution, Theia wants users to end up with a set of cameras that best meets their use case. So, we often discuss practical considerations like resolution, frame rate, integration capabilities and a number of other parameters that you can find here. In some cases though, a list of features just doesn't tell the whole story; there is always more to it. In an effort to fill this gap, we are posting a 4-part blog series that performs a more general assessment of the main cameras we have tested on site in our lab (Sony, Qualisys, Vicon, and Natural Point). Why these? Well, these are the cameras we have access to and tested rigorously. If you want your cameras reviewed on our blog, please reach out to us and we will provide our review after we receive your system.
Let’s start off with the Sony system:
Components: Sony RX0ii, Camera control box, switch, and POE splitters. The cameras record the video, the control boxes synchronize the cameras, the switch grabs the data, and the POE splitters power the control boxes using power over ethernet.
Setup: Each camera is attached directly to a control box, and a 2-inch USB cable connects the two. When they are mounted together, it’s a pretty small form factor. From the control box, a 1.5-inch splitter is attached to an ethernet cable, which goes back to the switch. So if you are using 8 cameras, you have 8 cables that feed back into the switch, which is connected to the computer.
Data recording and transfer: Sony provides a browser connection to the cameras that allows you to start, stop, download, and change camera parameters. Though it is through a browser, it is connected to the switch and not the internet, so you can still use this system when you are offline. When you click record in the browser, each camera synchronizes through the control boxes and saves the recorded video to the SD card. Typically, a handful of trials are recorded together, and then batch downloaded through the browser. In other words, the browser application is not saving the data directly to the computer, but rather to the SD cards of the cameras. You can, however, download the data through the switch without removing the SD cards from the cameras.
Calibration: If you are using the stock lens on the RX0’s, we calibrate them in-house and you just need to run the extrinsic calibration using the provided checkerboard. You can attach aftermarket lenses to these cameras to change the focal length, and if you do that, you’ll have to run the lens calibration on them as well.
Benefits: In general, the video quality that we see from these cameras is very good. They can record full 1080P at 120 fps, and perform really well in lower light conditions. The sensor is a 4K sensor, aliased to 1080P, so the image is very crisp. Since the data is stored on the SD card and not streamed to the camera, frame dropping really isn’t an issue. Another plus of using the SD cards for data recording is that it is very portable. You don’t need to worry about the laptop ethernet port overheating during the collection and dropping frames. Out of all of the cameras we are integrated with, these are by far the most portable.
Need to know: The first consideration is that the maximum frame rate is 120 FPS, so if you need to collect at a higher frame rate, it just isn’t possible with these cameras, even with windowing. The second is that you can’t integrate peripheral devices with this camera system, so it’s a kinematic-only solution. Also, depending on your workflow, because the data is stored on the SD cards and isn’t streamed directly to disk, there is an additional step to download the data from the cameras. One final challenge, which honestly hasn’t been a problem for us, but has been reported by others, is that the cameras run on battery when they are on, and if you collect too much, they can die. Charging the cameras requires them to be on standby, so between trials, you effectively need to turn them off. If, let's say, you collect for a minute and then break for a minute, the cameras will last, but some people want to do more than that, and in those cases, this may not be a great fit.
Overall, for a kinematic only solution, this system is a great fit!
Do you have more questions? Click here to learn more about using Theia3D with a Sony system.