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At the core of our motion studio are 7 cameras. Spatial
kinematic data are obtained by recording our subjects from multiple
views. These synchronized views are then analyzed to track moving
objects, reconstruct their 3D shapes, etc. Each research project
presents different photographic challenges; fortunately, the
motion lab can be rapidly reconfigured from the study of full-grown
tilapia swimming freely, for example, to high-speed macro photography
of tethered fruit flies.
Three of our cameras are the mighty Phantom
v12.1, manufactured by Vision Research Inc. At their maximum
spatial resolution (High Definition video) the cameras
can collect 6 200 frames per second. There are 16 GB of
memory. Allowing for 1.5 MB per frame (1280 x 800 pixels
pixels of 12-bit
grey level), this yields a recording time of:
(16×109 B)/[(6200 frames/second)(1.5×106 B/frame)] = 1.7 seconds
By reducing the angular field of view (reading a subsection of the detector) we can record at higher frame rates: 11 000 frames/second at 600 × 800 pixels, 54 000 frames/second at 320 × 240 pixels, etc.
Two of the cameras are
Fastcam 1024 PCI. They
have 8 GB of on-board memory, enough to record roughly
8 seconds at a
frame rate of 1 000 Hz at full spatial resolution
(1024 × 1024
Two of the cameras are Fastec Inline IN1000M1GB, manufactured by Fastec Imaging (maximum frame rate 1000 Hz at full resolution of 480 × 640 pixels). On-board memory is 1 GB.
The cameras continuously refresh their RAM with images at the user-selected frame rate and resolution; at lower spatial and temporal resolution, even more frames per second and/or longer recording times are possible. An electronic signal triggers the cameras to stop refreshing their memory. The trigger can be configured to signal the beginning of the measured event, the end, or a specified delay. It is often desirable to integrate a mechanical or opto-electronic trigger in the experiment. Since we have at least 1.7 seconds to respond, the cameras can generally be triggered by hand (with a mouse click or external switch) for exploratory recordings. All of our Photron and Phantom cameras can be synchronized on a frame-by-frame basis.
The video sensing elements are remarkably sensitive (Phantom v12.1 quantum efficiency is approximately 0.5), with an effective film speed of ISO 6400. Nevertheless, the maximum frame rate is often limited by the intensity of illumination that is possible: the exposure time per frame is at most 1/(frame rate). Depending on the illumination demands of the particular project, our studio uses high-powered LEDs, traditional incandescent photo-floods, non-Gaussian laser sheets, and the famous Fresno summer sun.
The image sensor of the Phantom camera is 26 mm wide. Subjects of this scale can be filmed at HD resolution with a 1:1 macro lens (Micro-Nikkor 105 mm f/2.8). Adding a reversed short-focal-length prime allows high-quality 2:1 magnification (13 mm field of view), 4:1 magnification (6 mm field of view), or 8:1 magnification (3 mm field of view) with excellent light-gathering power (f/1.7) for high frame rates.
Subjects for macro photography are mounted on a three-axis stage for positioning relative to the lighting system. Shown below is the setup as used for PIV recordings of bladderwort. The sample is in the cuvette directly in front of the camera lens.
Also visible at the lower left is the sheet-generating laser. A microscope is used when steering the mechanical micro-manipulator.
A second macro stage is used for general video recording in air.
Here 12 1-Watt LEDs are being adjusted to illuminate a tethered
housefly (in red at the center of the image) for high-speed videography
of its flapping kinematics. Links to larger (1.2 MB) images:
FlyFlap_14.JPG FlyFlap_16.JPG FlyFlap_19.JPG FlyFlap_21.JPG FlyFlap_22.JPG
FlyFlap_23.JPG FlyFlap_24.JPG FlyFlap_25.JPG FlyFlap_27.JPG FlyFlap_30.JPG
In addition, a standard stereo microscope (Leica S8APO) is
with a color
(Leica MC120 HD) capable of recording High Definition video at 30 frames/second.
Three different solid-state lasers are available for illuminating
particles in solution, with power up to 2 Watts in the near
infrared. The lasers were designed to generate
uniform lines on a surface for machine vision; in free space they
form a sheet with uniform side-to-side intensity and Gaussian sheet
waist. These beams are further modified as needed with
The microphones are differentially amplified in order to reject environmental noise common to both chambers. They are furthermore sealed in a glass dessicator, which suppresses low-frequency pressure fluctuations, and which in turn is placed in a acoustic isolation booth. For the study of bladderwort prey capture, audio recordings can extend over several days.
of the CSU Fresno greenhouse