How to Select High Speed Cameras
Images credits: Colorado State; Optronis
High speed cameras are a feature-specific type of video camera meant to capture events with minute, fleeting details that could not be captured by cameras with a standard frame rate. These types of cameras are capable of capturing sequences in excess of a 1,000 frames per second, and when the video is played back at a slower frame rate, the details of the event are more apparent. These are especially useful in scientific applications.
As an example, a hummingbird flaps its wings up to 80 times per second, too fast to distinguish flaps with the human eye. Yet a high speed camera slows the hummingbird's wing rate to an observable speed.
Video credit: Love Mushroom via Youtube
High Speed Camera Operation
High speed cameras function similarly to other types of video cameras, focusing light from the visible spectrum onto an image sensor which will turn the image into an electronic and recordable medium. Today, high-speed cameras almost universally use CCD or CMOS image sensors due to image capture advantages over film.
The functionality in a high-speed imaging device results from the frame rate, or the number of individual stills recorded in the period of one second (fps). Common video cameras will typically record about 24 to 40 fps, yet even low-end high speed cameras will record 1,000 fps. The fastest high speed camera records over one billion fps. In fact, selecting the proper fps is essential according to the application. Recording more frames than necessary results in a cumbersome file that can be difficult to analyze and save, especially when played back on equipment designed for standard speed cameras. Recording less frames than required will not reveal the transient motion for which high speed cameras are explicitly designed.
High Speed Camera Video Production
Shutter Speed/Exposure
Proper exposure and shutter speed is essential for high speed photography. For exposure, it is preferable to record scenes in complete darkness in conjunction with flash units which use extremely short flash durations. Recording in darkness is not always possible, so high speed cameras are regularly manufactured with exceptional shutter speeds. A high velocity object may be blurred in the image if the shutter does not adequately integrate the light on the sensor. This is from multiple line pairs (in colored, filtered sensors) registering the same edge of the subject. To prevent this, the shutter rate is recommended to be 10 times the subject's velocity.
Table credit: Motion Engineering Company Inc.
To arrest the motion of captured objects, either a very short exposure is required, or the camera must track the object which will blur the background.
A formula exists to calculate the maximum permissible exposure time (T).
T = L/500 x V
Where L is the largest subject dimension, and V is the subject speed per second.
Sensitivity
High-speed camera recording quality is also dependent upon the sensitivity. In general, a 600-watt incandescent light source four feet from the subject will provide enough illumination at 1,000 fps. For more demanding high-speed events, enhanced light sensitivity may be required. It is also possible to expand the camera aperture which will reduce the depth-of-field (or, range of focus), but will help keep the subject from blurring due to insufficient sensitivity. Keep in mind that monochrome cameras are more flexible in regards to sensitivity than color cameras.
Motion Analyzer
High speed cameras are often employed where the desired high-velocity event is difficult to predict. By utilizing an electronic trigger the high speed camera is continuously recording and replacing the oldest images with newer images. Once the event occurs, a machine vision sensor stops recording and provides the operator with the desired motion capture.
Selection tip: The lowest level of resolution acceptable for an individual application should be considered since the frame rates of high speed cameras result in extreme file sizes, and excessive resolution will only result in an even larger file.
Lens
Regardless of the image capture method of the camera, the lens remains the most critical component regarding high-quality image capture. Lenses are meant to refine optical aberrations that occur when recording video, and there is a wide variety of camera lenses for various recording scenarios. Lenses come in several standard uses and mounting styles.
CS/C/S mount lenses
Image credit: Bosch Security; Wikimedia
-
C-mount lenses have a flange-back distance of 17.5 mm and are required for C-mount cameras. By comparison, CS-mount lenses have a flange-back distance of 12.5 mm. Because of their shorter back focal distance, CS-mount lenses cannot be used with C-mount cameras. C-mount features a diameter of 1" and a 32-thread per inch mounting thread.
-
CS-mount cameras can use both C-mount and CS-mount lenses; however, C-mount lenses require either a 5 mm adapter or adjustments to the CS-mount camera. Because of their shorter back focal distance, CS-mount lenses can be used only with CS-mount cameras. CS-mount features a diameter of 1" and a 32-thread per inch mounting thread.
-
S-mount is a smaller mounting configuration used in devices such as PC cameras and board-mounted cameras. S-mounts use a M12 x 0.5 threads.
-
An F-mount lens utilizes a bayonet-style mount standardized by Nikon.
F mount lens dimensions
Image credit: Wikimedia
High-Speed Video Playback
With the exception of high-speed video meant for entertainment purposes (as outlined in the Video Camera Selection Guide), most video captured via high speed cameras is analyzed with specific programs on a computer interface. Consumer-grade codecs must offer file compression, and computers supporting the Microsoft MPEG4 codec will perform admirably compared to professional quality programs meant for industrial and scientific use.
High Speed Camera Specifications
Camera Mounting
Camera positioning is accomplished by the use of various types of mounts. Extendable and adjustable arms are common so cameras can be repositioned. Brackets are reserved for the most utilitarian of designs. Stands, such as unipods and tripods, offer a stable base while making the camera accessible to operators. Finally, many cameras come with the option of handheld or shoulder-mounted operation.
Industrial and scientific-based cameras are sometimes placed within a housing to protect the device from hostile environments. Industrial cameras are usually mounted with brackets or a separate type of mount that limits the device's movements. Due to the expense of high speed camera technology, the camera and any associated components are usually well protected. They also may provide resistance to mechanical vibration, which is common in manufacturing settings. Scientific cameras utilize whatever mount best suits the research, which may mean atypical placement. These mounts may apply by temporary means, may be exceptionally small, or the camera may not be mounted at all. Scientific cameras need the highest degree of flexibility among mounting options.
Entertainment cameras are usually valued for their aesthetic picture quality and high speed cameras do not typically meet the criteria for artisitc representation. As such, video captured by high speed cameras meant for broadcast must be reformatted. High speed cameras for entertainment purposes are most common in educational and athletic programming.
Camera jib; Tripod; Stainless steel bracket
Images credits: Production Central; Mr. Gadget; APG Vision
Camera Features
These specifications are often optional on video cameras, but depending upon the use they will enhance video quality.
|
Anti-blooming before/after Image credit: Astrosurf
|
|
|
|
|
|
Image credit: Apstas |
|
Image credit: Jarrett Security
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Image credit: Thermo Scientific
|
|
Image credit: JW Fisers
|
|
|
|
Image credit: Automation World |
High Speed Camera Applications
In regards to industrial applications, high speed cameras find use in automotive safety testing to examine crashes. Military applications include ballistics and wind tunnel examinations. Manufacturing companies employ high speed cameras in flying splice packaging, assembly and production lines, machine troubleshooting, and line spray analysis.
Scientific deployments include the medical industry, which will use high speed imaging to analyze water droplets, chemical injections, biomechanics, fluid dynamics, and stint deployment. Other research facilitated by high speed cameras are spectroscopy, live cell functions, and supersonic development.
Fighter plane breaking sound barrier; High speed camera focused on assembly line; Sneeze at 2,500 fps
Images credits: Telegraph UK; Copybook; Video credit: UltraSlo via Youtube
Resources
Motion Enginering Company, Inc. - High Speed Camera University
Wikipedia - High speed photography; High-speed camera
How Stuff Works - How High-speed Photography Works
Read user Insights about High Speed CamerasRelated Products & Services
-
CCD Cameras
CCD (couple-charged device) cameras are a type of image capture device that utilize an image sensor to register visible light as a recordable electronic signal to visually archive captured stills and video. Of the three types of digital cameras (the others being CMOS and CID), CCD cameras are the most developed and commonly used.
-
CMOS Cameras
Complementary metal oxide semiconductor (CMOS) cameras use image sensors that operate at lower voltages than charged coupled devices (CCDs), reducing power consumption for portable applications. Each CMOS active pixel sensor cell has its own buffer amplifier, and can be addressed and read individually.
-
Low Light Cameras
Low light cameras are a type of video camera with extreme photon sensitivity, and are excellent for recording in situations where only ambient levels of light are available. Common deployments include overnight surveillance and remote machine monitoring.
-
Video Cameras
Video cameras record live-action scenes that are available for viewing via a stored or transmitted video feed. This allows the user to create a permanent and detailed chronicle of events. Video cameras record dozens of pictures (or frames) a second that when viewed in succession, clearly distinguish the translation of an object or person over time.
-
Vision Sensors
Vision sensors are industrial products that automate decisions and processes by the use of video cameras linked to application-specific software on a user interface. These are also known as machine vision systems, and are useful for measurement, pass/fail decisions, and inspection.
