Difference between revisions of "Focusing system"
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* [[fixed focusing]] | * [[fixed focusing]] | ||
* [[guess focusing]] | * [[guess focusing]] | ||
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The '''rangefinder''' is an optical device to set the distance. There are two superimposed images (''superimposed image rangefinder''), or one image split in two parts (''split image rangefinder''). As you turn the focus control one of them is moving, left and right if the camera is hold horizontally, up and down if it is hold vertically. The focus is set once the two images coincide. | The '''rangefinder''' is an optical device to set the distance. There are two superimposed images (''superimposed image rangefinder''), or one image split in two parts (''split image rangefinder''). As you turn the focus control one of them is moving, left and right if the camera is hold horizontally, up and down if it is hold vertically. The focus is set once the two images coincide. | ||
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Only one digital camera so far uses this method: the [[Epson RD-1]]. Many famous film cameras use it however, most notably the [[Leica M]] series. There are many rangefinder cameras available on the used market, and these can be a very cheap yet high quality first camera. | Only one digital camera so far uses this method: the [[Epson RD-1]]. Many famous film cameras use it however, most notably the [[Leica M]] series. There are many rangefinder cameras available on the used market, and these can be a very cheap yet high quality first camera. | ||
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=== [[SLR]] === | === [[SLR]] === | ||
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A TLR or '''Twin Lens Reflex''' camera uses two lenses, one for viewing and one for taking. The light passing through the viewing lens is refected on an internal mirror and projected onto the ground glass at the top for viewing, focusing, and composing. Due to the use of a single mirror, the viewed image is reversed. ([[TLR|more info]]) | A TLR or '''Twin Lens Reflex''' camera uses two lenses, one for viewing and one for taking. The light passing through the viewing lens is refected on an internal mirror and projected onto the ground glass at the top for viewing, focusing, and composing. Due to the use of a single mirror, the viewed image is reversed. ([[TLR|more info]]) | ||
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[[Category: Focusing system|*]] | [[Category: Focusing system|*]] | ||
Revision as of 17:28, 23 February 2006
Focusing means setting the distance of the subject to have a sharp picture.
The simpler cameras (for example disposable cameras) have no focus setting at all: this is fixed focusing.
On most cameras, though, you focus by setting the distance on a ring around the lens. How do you know that distance, and how will you focus the image? On the simpler old cameras, you had no indication and had to guess it: this is scale focusing or guess focusing. The more advanced cameras had some kind of focusing help, the main types are the ground glass back, the rangefinder and the reflex finder. (Chronologically they appeared in that order.)
From the beginning of the 1980s the cameras began to incorporate an auto focusing mechanism: the camera determines the distance to the subject automatically. There are two main types of autofocus: active autofocus, where an infrared light is emitted by the camera and reflected by the subject, and passive autofocus, where the image transmitted by the lens is analysed for its sharpness by a detector inside the camera. Active autofocus is used by the simpler point and shoot cameras, and passive autofocus is used by the autofocus SLR cameras.
The different focusing systems are detailed in separate pages:
