Although our eyes perceive movement as a smooth and flowing phenomena, humans and animals both visually experience the world as a series of still pictures, spliced together to create our experience of the world. The human eye, as complex as it is, only operates at around 60 frames per second, meaning that it sends one still image of what it is viewing to the brain once every 16.66 milliseconds. This is why when we watch a car tyre or helicopter rotor in motion it may appear to spin backwards, as our eye only captures an image of it when it has completed just less than one full rotation. To put this into perspective, a bullet from a gun will travel 5.8 meters between frames viewed by the human eye.
High speed imaging is the process by which images are captured at much higher frame rates than the human eye can view. This higher frame rate allows minute movements to be captured in almost seamless motion and to be viewed by slowing them to a fraction of their pace. High speed imaging could logically be considered the opposite of time lapse photography.
Photron FASTCAMERAS have been used in countless different applications from research to broadcasting and everything in between. Being able to capture fast moving real world events at very high frame rates removes any guess work or assumptions about what happens during these events. This proves valuable in the installation and calibration of machinery, biomechanics and life sciences, physics, sports analysis and even atomic chemistry. With the correct lens selection cameras can even be attached to microscopes in order to view events too small for the human eye to see.
When purchasing a camera, you must also select a lens and make sure that you have a computer with appropriate processing speed and Ethernet jacks for running the camera. You must also have a mount (eg. a tripod) in order to stabilise the camera and have good lighting (how much depends on frame rate). For specialist uses like arc welding extra lens filters may be required.
Everything you need to take your own stunning high speed images can be attained through Blink Technologies.
Most Photron FASTCAM models allow the customer to select either a colour camera or a black & white camera, each having its own benefits when it comes to filming. When filming with ample light and in situations where colour images are important, this would be the best selection to make. Using a colour filter in front of the cameras sensor however will divide the cameras light sensitivity by 3 (3 primary colour filter) and in situations where less light is available and data is more important, black and white may be the best option.
People are often confused by each camera listing its maximum frame rate at full resolution and its frame rate at reduced resolution. Contrary to popular belief, reduced resolution does not mean reduced image quality, it only refers to manually adjusting the objective size of what is being filmed. Each pixel remains the same size and reducing the resolution does not stretch the pixels to fit the full frame but simply eliminates them creating a smaller filming area. This means less data is being collected with each frame and a higher frame rate or longer length of filming can be selected. This is particularly handy in situations where an object moves in a known trajectory or an event occurs at a known location.
It is important to recognise that Photron cameras can be set to film at frame rates as low as 1,080fps (45 times the speed of TV or movie recording) and as high as 2.1 million fps (87,500 times the speed of TV or movie recording). This is a wide range of frame rates capable of capturing a variety of different events. It is important to note here that as frame rate increases the amount of light required to film also increases, as the shutter is only open for a reducing amount of time. We must also be aware that as frame rate is increased, the amount of data being collected is increased and the length of video that can be taken will be reduced. Whilst 1,080fps may be appropriate for filming sports and other human movements, arc welding and machinery calibration would need much higher frame rates. As a general suggestion, try to work out how far the subject is moving and calculate at what frame rate the subject will move a reasonable distance between frames.
A camera’s light sensitivity refers to how much light exposure is required to produce an image. The higher the sensitivity is, then the less exposure time is required, meaning that the camera will be able to take better images in lower light situations. As discussed with regards to colour cameras, sensitivity for each camera varies depending on its specs.
Selecting a camera for your specific needs can be quite a difficult task, but the main things to consider are mentioned above. Make sure to select an appropriate frame rate for how fast the subject is moving, establish whether black & white or colour is required, know roughly what resolution you need and know how much light is available to establish what sensitivity is required.