RECORDING SPEED CONCEPTS

RECORDING SPEED CONCEPT

REAL TIME RECORDING

Real time recording is generally interpreted to mean the system is capable of recording at a standard rate of 30 frames or 60 fields per second. At this rate, persistence of vision in the human brain interprets this series of still images as having continuous motion. Real Time recording requires the storage of 216,000 images per hour and over 5 million images per day and should be avoided for the great majority of applications.

Most Analog Systems are limited by cassette capacity of 8 hours for VHS tapes and 3 hours for analog 8 mm tapes. Digital Recording Systems using Digital Hard Drive (DHD) media can store real times images for many days or even weeks depending on drive capacity and the resolution levels required. However, you are still faced with the problem of extracting data from the millions of images collected.

TIME LAPSE RECORDING

Time lapse recording is generally interpreted to mean the system is recording less than 30 frames or 60 fields per second. The time between the images is called the "Temporal Interval" or "TI". TI in standard time lapse recording units ranges from 20 images per second (TI = 50 milliseconds) to 90 or more seconds between images. Remember that a standard camera is still outputting 60 images per second and that combination or triggered systems can capture both time lapse and real time segments if desired

HIGH SPEED RECORDING

High speed recording is generally interpreted to mean the system is recording at greater than 30 frames or 60 fields per second and special non-standard cameras are required. High speed systems can range from 100 images per second (TI = 10 milliseconds) to many million of images per second. The major problem with the higher rates is the intensity of the light required to illuminate the subject for the brief duration of the imaging. If the subject creates its own light (say an explosion), it is usually less of a problem. But if the subject is alive or photosensitive, heat from the illuminators can cook it or the light level can destroy it.

Be careful to distinguish between applications that require high speed recording and those that require high electronic shutter speeds to freeze motion. Electronic shutter speeds to 1/100,000 are available on many lower cost standard cameras but still require high intensity illumination. An electronic shutter speed of 1/2000 to 1/5000 second is usually sufficient to freeze the motion of virtually all living things.