Cameras

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 on-board memory. Allowing for 1.5 MB per frame (1280 x 800 pixels = 1×10⁶ 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 pixels).

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.

Macro stages and microscopy

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
FlyFlap_31.JPG    FlyFlap_44.JPG

In addition, a standard stereo microscope (Leica S8APO) is equipped with a color digital camera
(Leica MC120 HD) capable of recording High Definition video at 30 frames/second.

PIV lasers

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 cylindrical lenses.

FBDS Hydrophonic Workshop

We have recently commissioned an audio studio for recording the activites of aquatic animals and plants.  It consists of an experimental volume (below, right) and identical reference volume (below, left), each equipped with a miniature hydrophone.

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.

Plant cultivation

Many species of aquatic and terrestrial bladderwort are cultivated in the Epiphyte Room
of the CSU Fresno greenhouse


Utricularia dichotoma

Fruit fly arenas

Shown schematically below is one of the setups used to observe walking behaviour of fruit flies. An overhead camera records four covered walking arenas simultaneously. They are illuminated by 8 × 1-Watt LEDs, which are softened by a hemispherical diffuser.