How to selelct high speed video cameras stand attachment High speed digital imaging camera

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.

C mount lens CS mount lense flang back graphicsS mount lens graphic

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 lens mount mechanical technical drawing

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 jibVideo camera tripodIndustrial camera mount

Camera jib;  Tripod;  Stainless steel bracket

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Camera Features

These specifications are often optional on video cameras, but depending upon the use they will enhance video quality.

 

 

  • Anti-Blooming: Saturation occurs when the light that is sensed exceeds a pixel's capacity to emit electrons. Excessive charge can bleed into adjacent pixels and cause bright spots or streaks to appear on the image, a condition known as blooming. Anti-blooming gates remove excessive charge and can significantly reduce blooming, but often at the cost of reduced sensitivity.

Anti-blooming software photo before/after

Anti-blooming before/after

Image credit: Astrosurf

  • Auto-Lens: Auto-lens operation is a mode in which the lens iris automatically adjusts to maintain a predetermined level of light on the image pickup device. Cameras with auto-lens mode may also provide automatic lens focusing.
 
  • Board Mount: Camera optics are mounted directly on a printed circuit board (PCB). Often, PCBs are components of larger devices.
 
  • Cooled Sensor: Sensors are actively cooled by a Peltier element or other method. Cooling reduces "dark current" noise and improves sensitivity.

Peltier cooled camera

Image credit: Apstas

  • Dome: Cameras are enclosed in a protective dome made from materials such as acrylic or polycarbonate. Typically, these materials are optically-corrected for accurate image capture. This can create a tamper-proof housing common for security use.

Dome tamper proof camera video ccd

Image credit: Jarrett Security

  • Gain Control: Automatic gain control (AGC) uses electronic circuitry to increase video signals in low-light conditions. This can introduce noise and, subsequently, graininess in the picture. Typically, AGC is disabled and specifications are presented with this feature turned off.
 
  • Gamma Correction: Gamma is the nonlinear relationship between the video signal level and the subsequent image element brightness. Gamma correction compensates for this nonlinearity in order to render the image true in color while providing intensity to the original object.
 
  • High Definition: High definition is a video standard that has higher picture sharpness, larger picture, more colors, and higher quality sound than regular video standards. The low-end threshold for HD video is considered 1,280 x 720 pixels.
 
  • Low-Light Camera: These are meant to be used in dark situations where an otherwise suitable camera will not have reached an exposure level capable of capturing an image. The cameras contain image sensors that are exceptionally perceptive of subtle light sources.
 
  • Machine Vision Sensors: Machine vision sensors have the capability to analyze events captured by its camera, and alert operators or make decisions based on the information collected. These are also called smart cameras. If they are not uniform machines, the camera is typically linked to a computer interface via a FireWire, USB, or Ethernet connection.
 
  • Outdoor Rated: Outdoor-rated devices are designed to withstand outdoor temperature variations, rain, snow, and other weather conditions.
 
  • Pan/Tilt: These devices have integral or optional mounting features enabling side-to-side (pan) and up-and-down (tilt) controllable motion.

  • Progressive Scan: This is a CCD design that allows acquisition of both even and odd fields at the same time. Each pixel contains information from one complete frame. This technology allows high resolution without the use of a mechanical shutter. Progressive scan cameras are used for image acquisition of rapidly moving objects and accurate dimensional measurements.
 
  • Radiation Hardened: Devices are designed to withstand high levels of radiation. These cameras can be used in nuclear facility applications, or in scientific research that will expose the device to radiation. These types of cameras almost always record in monochrome. CID cameras are commonly radiation hardened.

Radiation hardened camera

Image credit: Thermo Scientific

  • Underwater Rated: Devices are designed to work when completely submerged in water. This feature can be added with an aftermarket housing.

Underwater camera

Image credit: JW Fisers

 

  • Zoom: Cameras are designed with a feature that allows the device to closely focus on distant objects. Optical zooms offer better resolution than digital zooms.
 
  • 3D Recording: The camera has the capability of recording images in three distinct directional planes. This is helpful for recording the depth of an object.

3D industrial camera

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.

High speed imaging application camera High speed camera on assembly line 

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

 

Rochester Institute of Technology - Imaging and Photographic Technology Department - High Speed Photography by Andrew Davidhazy

 

How Stuff Works - How High-speed Photography Works

Read user Insights about High Speed Cameras

Related Products & Services

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