John_F wrote:
I keep seeing articles talking about Four Thirds. Does this refer to sensor frame size ratio? Need specialty lenses to use effectively. How does it compare to the old film standard of 36 mm by 24 mm image size?
Olympus wrote:
Four Thirds is a reference to the size of the image sensor. The image sensor for Four Thirds cameras is what is commonly referred to as a 4/3 type or 4/3 type sensor. These describe the type of sensor not the actual size of the light sensitive area, which is normally much smaller
The sensor measures approximately 22.3mm diagonally, not four-thirds of an inch, which would be about 33.87mm. Traditionally, the nominal size of image-sensing devices has been based on a method of calculation that was introduced when vacuum image-sensing tubes were first invented.
At the time, the outer diameter of these early 'vidicon' tubes was used to indicate their size. Unfortunately, this convention has remained despite the many advances in imaging technology that have since been made, and so the designation, "a four-thirds-inch sensor," can be a source of confusion. For this reason, many people now prefer to use the word "type" instead of "inch" when discussing the size of digital image sensors.
Four Thirds is a reference to the size of the imag... (
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