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WP's SloMo FAQ - High-Speed Camera Know How


High-speed camera SpeedCam Visario g1
Digital HD high-speed camera, 10 000 frames/sec

Digital high-speed camera - the popular ask and answer game

Bursting soap bubble
Bursting soap bubble
slowed down 500 times

Elementary questions coming up, when talking about digital high-speed cameras and slow motion systems. Not all, but a lot about high-speed and SloMo cameras.
This here is not an advertisement site - links to various manufacturers and systems you will find in [SloMo Links].

Sample sequences:



And what do I see here? It's just a video camera!

Some typical high-speed camera technical data:


Well, it's just a little bit more: Fully digital high-speed video cameras achieve at TV quality (PAL/NTSC or even better than HDTV) more than 1 000 frames per second (like progressive scan, i.e. without interlacing in black-and-white or True Color). By reducing the resolution (binning) or the format (reading a part of the sensor only) system depending a maximum framing frequency of several 10 000 up to much more than 100 000 frames/sec is possible. Even just more than 1 million frames/sec are technologically feasible by that. (By the way there also exist the abbreviation fps for frames per second and Hz for 1/second.)
The combination with special strobe lights for multi-time exposure permits frame rates far above this.
Single to multi-channel systems and even shock resistant versions are available.

Concerning expenditure and capabilities it is better to speak of an optical measurement appliance than of a (video) camera.
Consequently several high-speed cameras additionally offer frame synchronous analogue and digital data acquisition channels.


Digital high-speed camera: Where is a device like this used? - It seems to be very exclusive!

No really it isn't. Such cameras are used e.g. in automobile industry and its suppliers (crash test, air bag, tire engineering, hydraulics, ...), in special mechanical engineering (packing machines, machine-tool building, robotics, lumber industry, ...), in quality assurance (material testing, crack testing, ISO 9000/CE documentation, control, ...), in mass production (cable making, plug and socket connection, rack off facilities, welding facilities, ...), in service use (common adjustment, printing industry, printed circuit board assembly, chip card manufacturing, ...), in medicine (gait analysis, rehabilitate and recovery, ergonomics, forensic, ...), in sports (training, documentation and teaching, material development, movement analysis, ...), in advertising and show business (TV adverts, special effects, music videos, ...), in heating and combustion engineering, in animal research, in mining, in structural and civil engineering, in sportswear industry, in kinematics and fluid mechanics science, in air and space engineering, in military engineering, ...


How can the camera work with this speed? - The sensor must just be »tuned« very well!

Well, of course, a special sensor designed for high-speed demands is used. The performance of high-speed cameras, however, derives less of the poor clock rate, but of the parallel structure. Normal speed CCD or CMOS cameras read out the sensor just at one single spot. A frame (charges in the sensor matrix) is pushed pixel by pixel from this read out line into the processing electronics. Then the remaining frame is shifted in one step by one line in order to fill this read out line again and the read out process starts once more. And so on until the sensor is regularly read out empty completely. Because so an information spread over an area is transformed into a serial data stream one speaks of serialization.

Sensors of high-speed cameras are usually designed in a very parallel structure. Multi-frame single shot cameras expose the sensor several times at different areas and/or just use it as memory as well, which is read out afterwards with normal speed. In sequence cameras the sensor offers several independent read out channels including electronics. Casually spoken one has several cameras in the same housing. For instance the »VGA class« CCD sensor HS0512JAQ of EG&G Reticon (ca. 1995) has 16 of these read out channels, the »HDTV class« CMOS FhG/CSEM Cam 2000 sensor (ca. 2001) offers 32 analogue and the megapixel CMOS Photobit PB-MV13 (ca. 2003) 10 digital ones. The image data are buffered in memory banks via a wide bus or channel architecture from where they are read out with standard speed.

Usually the sensor runs with a fixed clock speed of several ten to some hundred megahertz with high pixel count imagers. So the maximum read out rate (pixels per second) and the maximum framing frequency (complete sensor per second), resp., are limited. When one wants to exceed this nominal frequency, one will have to decrease the number of pixels per frame to be read out. Just because of the fixed read out rate. One achieves that by reducing the read out area step by step. Thus quite a few thousand up to more than one million frames per second are within ones reach. But take notice in view of smallest »peepholes« such a top score is more useful for sales promotion than for application. Not to mention the extreme demands for illumination due to short times of exposure.


Does one really need a camera with so many frames per second? - My camcorder is able to provide slow motion as well!

Indeed it is, but it usually is only capable of 25 or 30 full frames/sec, possibly 50 or 60 interlaced half frames per second only. In between a lot of information is lost. (One starts to talk about high-speed cameras when frame rates of more than 160 frames/sec and a serial of least three photos in a row or with 125 frames/sec with a time of exposure less than 1 microsecond are achieved, refer e.g. to EU Dual Use Regulation Export List paragraph C, 6A003.)

Practice-oriented example: A comparison of different chisels of a turning lathe and their shavings is to be done. The workpiece rotates with 3 000 rpm, which are »ridiculous« 50 revolutions per second. Nevertheless, with 25 (30) frames/sec only each second revolution is caught. With 1 000 frames/sec each 18° a frame is won, thus 20 of one revolution.

Igniter explosion shot with a high-speed camera
Gas and particle exhaust of an igniter

Which reminds us of the next item: The object to be shot does not stop in best pose during the picture is taken, but continues moving. A single picture covers the MOVEMENT of the object during a CERTAIN SPAN OF TIME, i.e. the time of exposure. (This as difference to a flip book ;-)

The photo on the right shows one frame out of a sequence shot with 1 000 frames/sec. One sees the blow-out of an initiator (size approx. like a finger tip), e.g. as used to start the pyro charge of an airbag or a rocket kit, about 3 milliseconds after ignition.
While the gas cloud eddies are sharply captured by a time of exposure of 1/10 000 seconds, the blown out red-hot particles, however, appear as stripes only, due to motion blur. The already reduced time of exposure is not short enough to freeze their movement.

Practice-oriented example: The workpiece mentioned above has a diameter of 100 mm (approx. 4 inches), the exposure is 1/1 000 sec. Then 18° would be 15.7 mm (approx. 0.62 inch) the surface of the workpiece rotates on. If this is too much, the time of exposure will have to be reduced (and/or the frame rate has to be increased). How, you will find at [SloMo Tips] in this site.

Concerning movement analysis one has take into account the Nyquist-Shannon-Kotelnikov theorem of sampling: To reconstruct (an oscillating) movement one has to use at least the double scanning frequency than that (frequency) of the movement.

Practice-oriented example: A valve or a loud speaker let out the chamber tone »a«, they oscillate with 440 Hertz. (That's about the sound of the »ahhh« one says at the dentist.) To follow the movement of the membrane one needs at least a frame rate of 880 frames/sec (1 Hz (Hertz) = 1/sec). As practice shows even with much more.

A short comparison with military demands shows what extraordinary frame rates must be taken into account.
Practice-oriented example: One wants to see the bullet leaving the barrel of a standard military gun like the AK-47 (Kalaschnikow) or the G3 (Heckler & Koch). The V0 of the projectile at the muzzle exceeds two times the speed of sound, let's say 680 m/sec (2 230 feet/sec). Thus during one thousandths second the projectile moves more than 0.68 m (2 feet 3 inch) and you will get a stroke of this length as image, if you do not reduce time of exposure. With a time of exposure of one ten thousandths second the stroke length reduces to just about double the projectile length only. That implicates when you want to watch a bullet penetrating the target, you will need frame rates of several thousands to some ten thousand frames/sec at least.
By the way: Pistols and revolvers fire their bullets with about 275 m/sec (~ 900 feet/sec) and more, some shells of artillery and tank cannons reach more than 1 600 m/sec (~ 1 mile/sec) and additionally rotate round their longitudinal axis.

Therefore - do not underestimate the necessary frame rate, especially not with rotating objects and explosions.


How long can one record? - Camcorders just allow to change the memory card or can be integrated in a net!

The limitation is not the memory medium alone. One can also integrate a harddisk drive or connect the camera with USB or Ethernet, etc. And it is really done. The image data, however, are generated so fast that a common interface is not able to read out them from a therefore necessary buffer memory. A megapixel sensor generates at 1 000 frames/sec just about 1 GByte of data per second. Therefore the USB connector is rarely seen at fast high-speed cameras with high resolution. Refer also to [SloMo Image].

With moderate demands for resolution and frame rate it may be possible to select a low end camera system capable of directly writing the image data to a harddisk of the control device, as a rule a notebook, during a longer period of time. That works about with VGA resolution and 100 to 200 frames/sec.

In the other direction, if one desires a usable resolution at extreme high frame rates, even the connection between sensor and buffer memory turns to time critical. Then it is not made of separate ICs, but memory cells or memory areas are directly arranged on the sensor or even around the pixel. Of course, the recording time is further limited by that.


Isn't the recording capacity of at most a couple of seconds too short? - Malfunction of the machine I intend to monitor occurs after some minutes or even hours!

Balloon burst
Bursting waterfilled balloon

No, actually it isn't - because what goes fast, is often over in a moment. Not to mention the image memory of digital high-speed camera systems is organized like an endless loop buffer. Due to the installed hardware capacity, frame rate and resolution it is overwritten after every e.g. 4 seconds. The system is able to lie in wait in this mode for hours or days. After it gets its trigger signal the real grabbing is made the overwriting process is stopped. What one really gets can be pre-selected with the trigger position.

Practice-oriented example 1: In a facility for filling bottles break into pieces at a certain place but in uncertain intervals. One is looking for the cause. The camera is adjusted towards the scene of interest and the trigger input of the camera system is connected to a microphone. The trigger position is set to 100%, i.e. end position. The camera system is running in record mode overwriting the image memory (here e.g. sized 2 seconds). The sound of the breaking bottle releases the trigger. The recording stops and in the image memory of the camera system remains the 2 seconds »history« made before the sound has caused the trigger.

Practice-oriented example 2: An analysis of the start phase of a sprinter in a 100 m competition is to be done. The trigger of the camera system, with e.g. 1 second image memory extension, is set to 25%, the trigger input is connected to the starter's pistol and the system is set to record mode. Then one catches 0.25 seconds before and 0.75 seconds after the start shot.

Some high-speed cameras offer the chance to use the image RAM sequentially. This partition mode means one can shot several short independently triggered takes without the image RAM being filled at once by just a single sequence. More about calculating the memory demands you will find at [SloMo Data] in this site.
And finally something about duration: When you watch the 4 seconds you have recorded with 1 000 frames/sec, you will do this slowly - that's the idea and purpose of slow motion. With a replay speed of e.g. 1 frame/sec you will get regular movies nearly lasting 67 minutes, but often with a rather meager plot. Therefore usually the systems offer the possibility to cut the sequences before storing them on a durable storage medium.


Isn't the resolution too low? - Digital photo devices have several megapixels, at all!

No really it isn't, one has other claims to photos. Often detail enlargements are necessary, because the digital photo devices offer a very restricted focal length adjustment only. Moreover the images are stored (not lossless) compressed to overcome the huge data flood. Thus they really have not the advertised resolution. And somehow one has to get rid of the data amount: An uncompressed megapixel image has at least 1 MByte, with True Color even rather more. And practically spoken: What device just permits to replay streams of real megapixel images with data rates of GByte/sec fluently?

Besides a higher resolution just causes smaller pixel, because the sensor size is even limited by the lens design. Smaller pixel, however, are more susceptible to noise and usually demand more illumination.

VGA, PAL/NTSC and HDTV formats
VGA, traditional and new TV formats

Therefore a comparison with broadcasting and video technology is more useful, because it is primary based in the moving frames sector as well, and I suppose TV equipment is within everyone's reach (or memory ;-). The visible resolution of a PAL/SECAM (CRT-) TV set amounting to 720 columns x 576 lines (not 768 columns as the 4:3 side ratio seems to claim) is reduced by S-VHS recorders to 576 x 400 and by VHS recorders to 576 x 240. From TV sets according to NTSC norm out of 720 columns x 480 lines (not 640 columns as the 4:3 ratio seems to claim) corresponding lower resolutions are generated. In which one should take into account the interlace mode: One does not see one image but two half-frames inserted alternating line by line like two combs. Just spool a video tape in single step mode to a fading then you will recognize it very well.

So the real full frames, so-called progressive scan, of smaller digital high-speed cameras up to roundabout VGA resolution (640 columns x 480 lines) are not so bad at all. And the up to date megapixel-systems show in parts higher quality than HDTV (1280 columns x 720 lines progressive or 1920 columns x 1080 lines progressive) and reach or even exceed high-speed film camera standard. Especially if the resolution for Digital Cinema (2K: 2048 x 1080, 4K: 4096 x 2160) is in focus - with appropriate low frame rate and high financial expenses this presently is achievable.

Practice-oriented example: A movement analysis of a javelin-throw is to be done. The scene of interest is 5 m x 5 m. Is it possible to see the javelin bending and rotating? In an optimum image each pixel of e.g. a 512 x 512 black-and-white sensor represents an area of less than 10 mm x 10 mm so one can see and even read an inscription on the javelin.

As experience shows resolutions of 128 x 256 pixels in black-and-white generally provide frames of adequate quality for technical evaluations. For broadcast applications the entry levels lies (far) above 512 x512 and with True Color, i.e. at least 8 Bit or already 10 Bit per color channel of the sensor.


Isn't there a need for a lot of experience and expensive equipment? - At least one does special shooting!

Usually one does not need special equipment for industrial and most scientific shooting. (Shooting for Movies/TV is a different business.) In most cases one can use standard C-mount lenses (2/3 inch format or bigger) and together with appropriate adapters (€/$ 50.- at your local photo dealer) one can handle with common photo lenses, too. And even facing extreme situations, e.g. shooting in cramped locations, hard to reach spots or under water, one benefits of the broad supply of photo and video industry. And as illumination source a 500 W halogen (tungsten) spotlight bought in the supermarket just around the corner is often sufficient enough for technical sets.

Naturally competent support by the supplier is combined with the systems. The demands for basic photographic knowledge concerning technical shooting (machinery adjusting jobs, ...) are not very sophisticated. And in general the systems offer a control software easy to use.


Isn't the control too difficult and the system too susceptible for industrial environment? - In fact one operates with a special camera at a Windows PC!

No it isn't, in general the camera systems are designed for their typical field of operation. So there are transportable devices in a single box (even without demand for an additional control computer), or ones based on tough industrial computers like used for industrial control devices and telecommunication systems. Or the compact and rugged camera offers stand-alone capability and is controlled by a notebook or a remote control if necessary.
Also systems completely suitable for crash tests are supplied, specified for high acceleration loads to fulfill the demands of automotive industry for on-board crash tests and for airborne use.
Some systems can operate without mouse and keyboard only with remote control, often additionally accessed by Ethernet or other networks. Sometimes the image section of the camera is nearly self-supporting and keeps the contents of its image memory during a hang up, a power failure or a brown-out or the complete camera can even operate in battery mode.

Please consider that in a big car crash test some dozen cameras partly from different manufacturers must reliably work inside and outside of the vehicle spread over various locations. And this covers operating as well.

Casually spoken: Everybody who is able to operate with a video recorder or a camcorder can handle the industrial systems. Besides - everyone has a little bit PC experience and those who are afraid of working with a keyboard may be satisfied with the handful of keys offered by the remote control.
And concerning endurance: Some cameras and systems ride on crash test sleds, partly three times a day - for month without malfunction.


Why is the high-speed camera so expensive? - A good video camera with PC and frame grabber just does not cost more than €/$ 2 500.-!

Well, such a PC system makes 50 to 60 half frames/sec. 1 000 full frames/sec are 20 to 40 times faster - so far the price seems to be more than fair. Besides high-end high-speed cameras are true camera systems - better: measurement devices - and not just a frame grabber thrown in a standard PC housing. Not to mention it isn't necessary to buy such a system, one can also rent one from the manufacturer or a service provider at about 500 to 1 500 € or $ per day.

Overview of prices for high-speed cameras
Estimated entry level prices for digital high-speed cameras, 2010/11

The enormous price margin in the figure shown on the left is due to on first hand dealing with large-scale manufactured consumer products or standard image processing with usual data transmission rates, while on the second hand dealing with high-grade scientific measurement devices with special techniques which are partly individually designed and built by scientists and engineers.

Technology steps cause a non-smooth and non linear behavior of the curves. Up to about VGA resolution and about 100 to 200 frames/sec one can directly move the image date through usual interfaces (Ethernet, FireWire, CameraLink, ...) to the PC and its harddisk. With higher data rates (faster camera, higher resolution) one has to place the memory inside the camera or must connect the camera via a special interface device (framegrabber, DSP, ...) inside the PC, refer image left below. With frame rates starting at some 100 000 frames/sec even this isn't sufficient enough. The memory is integrated in the sensor directly grouped around each pixel.
Special demands for military use, crash tests or broadcast (movie and TV) increase the costs.

The start price for new equipment with VGA resolution, monochrome and about 500 frames/sec amounts to less than €/$ 10 000.-. With lower frame rates of roundabout 200 frames/sec the €/$ 2 500.- mentioned above maybe possible. For instance there are available some standard consumer camcorders and cameras capable of some hundreds (half-/full-) frames/sec and above with VGA resolution in short sequences and prices of partly less than €/$ 1 000.- or even €/$ 500.-.
One, however, has to accept really rather low resolution (often not clearly stated in the data sheet, but drastic below full resolution), reduced image quality, restricted adjustment and limited upgrade chances then. Not to mention the lack of connectivity for control signals. The »upper class« - megapixel at 1 000 frames/sec at least - costs even several ten thousands of €/$. Fast (single shot) cameras in the some 100 000 frames/sec region cost some hundred thousand €/$. (Open end price list, of course ;-) Besides one shouldn't forget the equipment, especially the expense for lighting and the costs for control and analytic software.
A small rental and second hand market exists - just ask a manufacturer or service provider for demo or used systems. Refer to [SloMo Links] for detailed info and links.

CCD matrix sensor integrated circuit
Hand optimized color sensor

The OEM black-and-white chip is opened and a RGB stripe filter on glass substrate is adjusted with high precision (±1/4 micron) full plane on the sensitive area optically controlled by the operating(!) sensor. The remaining cavity is filled with special polymers to protect the bare silicon die and the bond wires and baked in an oven. (By that the high-g ratings during crash test applications are guaranteed, too.)

Just click on the image on the right to see what is happening during the operation.

Seriously: The components, especially the sensors, are special designed with high technical expenditure built in small series with low yield, additionally selected several times and therefore very expensive. The sole sensor often costs much more than a complete high-end video camera. And of course, the development and manufacturing costs for the design in of the complete system are not insignificant, too, because the camera systems have nothing to do with normal video at all. They provide digital images in a special format. The camera heads wouldn't work together with a video recorder or a CCIR (= TV) monitor at all. Just special electronics inside the camera or inside the control unit generate the standard video signal only.

Once a qualified visitor remarked after the tour through the lab:

That's not high tech, you just build highest tech.


What are the future trends? - Always one wants higher resolution!

Well, indeed, semiconductor performance will increase from generation to generation, but like now there will be limitations due to data transfer rates. Thus processing and displaying the images will probably cause a change of the aim: from the hunt for speed towards improvement of the light sensitivity, less higher frame rates, but full resolution with higher dynamic/color depth and better image quality - Full HD 1920 x 1080p and movie industry are just in sight. Further on the system intelligence will be gathered in the camera head - like a camcorder. Ultra fast cameras with Millions frames/sec especially address the military research sector, small (rugged) cameras industry and automotive.

Nevertheless or just therefore there will be further diversification - a growing market for smaller camera heads will arise, too. They can easily be put inside a crash test vehicle or a machine and then for multi-channel devices the system controls, intelligence and even memory are put in a common used control unit (again). Key word: separate camera head.
Additionally from the image processing sector (also:»machine vision«) a lot of cameras show interesting specs for numerous applications. Often VGA resolution or a bit above at some hundred frames per second is sufficient enough. And these cameras are rather inexpensive compared with the traditional high-speed cameras. Besides they offer a moderate data amount for the image processing in real time and case-by-case they are able to work as long-term recorder directly writing their data on a harddisk.
Concerning network integration the GigE Vision interface (Gigabit Ethernet for »machine vision«) is a high flyer - a connection based on Gigabit Ethernet with complementary control commands - but it is, however, only intended for standard cameras used in the industrial image processing sector at first. With Power over Ethernet (PoE) a camera eager for current is simply slowed down by a non-existing potent destination device (power out of the notebook battery?!). More interesting for high data rates are professional studio technique interfaces like HD-SDI and from consumer field USB 3.0.

Coming from consumer market several well-known manufacturers, especially Casio (e.g. EXILIM EX-F1), address with camcorders and cameras, resp. the lower price and feature segment of the high-speed camera market. (Refer to [SloMo Links] for detailed info and links.)

More and more high-speed cameras are professionally used as measurement devices with appropriate analysis software. One does not watch the sequences only, but makes them automatic calculate movement parameters like place, velocity, acceleration, ... This is taken into account by integrating data acquisition channels, which are able to record and store analogue or digital signals synchronized with the frame rate. The rest is processed by suitable evaluation software, at least in parts fully automatically.


Isn't it possible to build a high-speed camera smaller? - Already there are tiny webcams and surveillance cameras!

High-speed camera concepts in comparison of size
Digital high-speed camera concepts

In principle, it is. But in contrary to a comparatively simple video camera a lot of complicated electronics are necessary to handle the generated data amounts (up to and over GBytes per second). When transmission of data isn't possible any longer, they will have to be buffered inside the camera. The additional demand for a »smart« or »intelligent« camera (i.e. with image processing capability, different memory modes and other features) causes - spoken in simple terms - the integration of an almost complete PC even possibly with a mass storage medium and buffer battery. That all needs space - and yet worse - produces a lot of waste heat. Up-to-date high end cameras can reach about 100 W and even surpass - in a housing with the size of a shoe box.

In the figure on the left some construction concepts of digital high-speed camera systems with rough comparison of function and size. Of course, there are kinds of mixtures and special solutions. So the image memory of very fast cameras can be integrated in the sensor. The resolution and memory size, however, are strictly limited by that.
The green card shall show a PC card (framegrabber, DSP board, ...), the red line connection possibilities (image and control data).

Legend: RAM = image memory; µC = microcontroller or processor; A/D = analogue to digital conversion (often already integrated in the sensor)
The standard connection can be e.g. (Gigabit) Ethernet, FireWire or CameraLink. Even a HD-SDI interface for a mass storage device could be possible. The special connection depends of the individual manufacturer.

Moreover if the camera has to withstand high mechanic loads (shock, vibration) with durability and repeatedly, one will avoid active cooling using a fan. Only the housing is used as passive heat sink and demands a certain (surface) size. Besides desired robustness and shock strength force certain material thickness, lockpin and fastening systems, refer to the exploded assembly drawing (pdf, 146 kB) of a crash-proofed digital high-speed camera.
Besides one must take into account that in general due to the shorter times of exposure compared with conventional cameras the pixel do not turn to be too small and therefore get too light insensitive. That makes the high-speed camera sensors grow and thus increases the size of cameras and lenses. (Usually not combined with cheap prices.)

Nevertheless, or just therefore, various systems for different applications exist. For instance such with one or more separate imagers (camera heads) connected to a basic station with the main part of the camera and control electronics inside.


A buyer's guide for high-speed cameras

Why not just buying a camera with 1 million frames per second? - It would cover all speed demands!

Easy, indeed. But each user has different demands. It is not only a matter of costs, it is also a matter of equipment (e.g. illumination), experience, experimental set-up and so on. There is a costly trade of between resolution, frame rate and duration of recording.
And it makes no sense to shoot some 10 frames in ultra short time of a process that last half a second. You won't capture the complete process and the resolution may be too low to visualize structural details.
On the other side a too extreme slow-motion will turn the movement study in a boring thing. So many of the sequences shown in animal films are shot (or replayed, resp.) at a maximum of some hundred frames/sec. Even if the speaker tells you cameras with some thousand frames/sec were used. Just imagine a cheetah at top speed filmed with 1 000 frames/sec moves about two finger wide from frame to frame.
And when slowing down this ultra-fast high-speed camera? Well, why purchasing an expensive camera with features you will never use, or which shows its limitations somewhere else just due to its speed, e.g. resolution, when there are available cameras much more suitable for your application? 1 million frames per second or more are not for free.
Then, however, if one hasn't really extraordinary demands and isn't too modest concerning performance figures it won't be impossible to find a standard »one fits all« device.


How to get started? - So much has to be taken into account!

Exactly, that's all right so far. In contrast, however, to a couple of years ago a lot of vendors bustle in the high-speed camera market, or what they want to sell you as that.

Figure of velocities
Some selected velocities

Why not just turn the tables and use the demands of the application as guidance only? The most expensive or the fastest camera system with the highest pixel count need not always be the best qualified one. Often it is exclusively designed for special applications and needs adequate accessories (illumination, control devices, equipment, ...) and user know-how.

The figure on the right gives you some insight what happens in a microsecond or what is behind the unit meter per second.
1 km/h = 3,6 m/s; 1 m/s = 0,2778 km/h; Mach 1 = speed of sound (in air) (1 meter = 39.370 inches = 3.281 feet = 1.094 yards)

Some other examples: An airbag is pumped up within 30 milliseconds. The human eye-shut reflex needs about 200 to 250 milliseconds.
So it definitely makes no sense to shoot human movement with much more than 1 000 frames/sec ore even 100 000 frames/sec. And even a car travelling with 50 km/h (about 31 mph) moves from frame to frame less as wide as a finger. The impression of dynamic is completely lost and you will fall asleep when watching replay.
Or to say it with Douglas R. Hofstadter's Zeno: »Movement unexists« (aus Gödel, Escher, Bach: an Eternal Golden Braid).

These pages here should just bring a little light in the darkness, should show relationships and should explain basic characteristics - thus should offer some kind of a small buyer's guide for »real« high-speed cameras. Thus just a small educational lesson about speed, frame rate, resolution, illumination, image quality and data.


A checklist proposal for selecting one's own high-speed camera

  1. The speed of the object in the image plane and the desired resolution in time, resp. provide clues for the necessary frame and shutter rates: How many photos per second are necessary? How much movement during time of exposure and especially between photos is tolerable?
    Some proposed and typical, resp., frame rates (frames per second, fps): human movement analysis and special effects about 100 ... 250 fps, very fast sports and industrial adjustment about 500 ... 1 000 fps, car crash test about 1 000 ... 3 000 fps, air-bag tests about 3 000 ... 5 000 fps, explosions, cracks, gunfire and rockets in flight up to about 10 000 fps, lightning flashes, discharge and rifle bullets about 10 000 ... 100 000 fps, shells and penetration 100 000 ... 500 000 fps, chemical and physical reaction research about 100 000 ... 1 000 000 fps and above.

  2. The spatial resolution and the size of the scene affect the lens selection (field of view) and only then the sensor resolution (pixel count). Take notice of possibly correlation between resolution and frame rate. Expensive steps in technology are combined with sensor resolution.
    Some proposed pixel resolutions: industrial adjustment and gait analysis about 512 x 512 or 640 x 480 (VGA, PAL, NTSC) and less, automotive about 1000 x 1000, special effects 1280 x 720 (HDTV) and Full HD 1920 x 1080( 16:9!) or better, up to Digital Cinema resolution and above (3D).
    Even low resolutions, e.g. 256 x 256 and even below, will be able to provide results of sufficient quality for industrial applications if real black-and-white cameras are used. Just have a look on the example sequences shown in [SloMo Clips]. A high resolution gets interesting when enabling covering the scene with less cameras.

  3. The recording time is a severe cost driving factor. Using intelligent trigger modes leads to a reduction of efforts - according to comedian Otto Waalkes »The shorter the ssst, the faster the bang!« It needs not always a long time recorder with possibly reduced frame rate and resolution at high costs.

  4. Saving, postprocessing and wishes for image processing, resp., rise demands for technology, image quality (HDTV, movie?), access (download times!) and storage (memory card, LAN + RAID, HD-SDI, ...).
    Just saving (downloading from the camera memory) alone can be at first sight astonishing time consuming or turn expensive due to the high performance interfaces and media.

  5. Light is a precious good, because time of exposure often is short. For e.g. 1 000 frames/sec mean that there is not more than 1/1 000 second time of exposure for each single frame - if ever.
    Especially for outdoor applications (depth of view, clouds!) and ballistic shots (reduced time of exposure by a shutter in order to reduce motion blur) light sensitivity is an important criterion. Monocolor could be an option.

  6. Options (improved shock resistance, extended temperature range, ...) and equipment (clock dividing devices for synchronizing, special lighting, ...) can considerably push the price. With a high-speed photo camera out of the consumer sector, however, one will not have much fun in harsh industrial environment.

  7. Do not forget to check integration in your environment and systems (PLC and IT connections), control software (adequate, stable, easy to use?) and special equipment (special lenses, control devices, ...).
    From somewhere the (suitable!) trigger signal and possibly other control signals have to come from and possibly generated control signals (strobe out = exposure active, all armed = ready for shot, ...) and image data have to be sent to somewhere, too.

  8. Out of practical experience: Have an eye on adequate and suitable (robust) housing, connectors and cables. Just imagine - how often a RJ45 patch cable can be plugged/unplugged by an unskilled hand.

  9. Check whether the equipment is modular concerning upgrade options, exchange, service and maintenance/repair. The technology and product cycles, however, fortunately are not as short as in computer business.

  10. Try to get a demo and perhaps think about rental service. This can make the start easier, reduces costs and provides experience. Especially concerning tricky shooting setups. In order to reduce costs also ask a manufacturer for rental, used and demo equipment. Possibly better than creating it on your own or buying it anywhere.


Just some additional technical sensor info, tips and tricks for shooting you will find here:





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Update: V8.4, 2012-03-02