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Photography Question 
Clay Mercer
 

full frame cameras


what is the difference between slr and full frame cameras


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9/2/2008 10:10:21 PM

 
W.   
Hi Clay,

there are dSLRs with 'full frame' sensors, which are practically the same size as 35mm film frames: 36x24mm. Most dSLRs, though, have smaller sensors, like 'APS-C' and others.

Lenses on full frame dSLRs have no crop factor. Lenses on non full frame dSLRs do. Usually 1,5 or 1,6 (Olympus'/Panasonic's '4/3rds' sensors have a crop factor of 2,0).

Bigger sensors beget better image quality and better low light sensitivity.

Check out: http://en.wikipedia.org/wiki/Sensor_size

and
http://upload.wikimedia.org/wikipedia/commons/e/ec/SensorSizes.png

Have fun!


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9/3/2008 6:14:00 AM

 
Alan N. Marcus   Hi Clay,

Early photographers had great difficulty aiming their cameras. By aiming, we are talking about pointing, focusing and composing. Most early cameras used a viewfinder system. The viewfinder works like a telescope mounted backwards. The photographer looked into a viewfinder and was presented with a miniature view of the subject. The view somewhat resembled what the finished picture might look like. These early viewfinder cameras did OK but focusing was hit and miss plus they failed badly when making close-up pictures.

One idea used to improve viewing and aiming that worked fairly well, was to install a second lens, just above the picture taking lens and cause this upper lens to send a duplicate of the taking lens image, to a viewfinder. Using this viewfinder image, formed by the upper lens, a photographer could aim, compose and focus while allowing the picture taking lens to do its job uninterrupted. Sorry to report that the viewfinder image, while good, was award to use. To solve this problem a mirror was installed to reposition the viewfinder image. Now the photographer had a wonderful view allowing good compensation and focusing. These cameras were called “twins lens reflex cameras” introduced by Franke & Heideckel in 1928 as Rolleiflex . The word reflex is Latin it means an image as seen in a mirror.

The twins lens reflex camera was good but failed to focus and compose properly when making extreme close-up pictures. The next idea was to install a mirror behind the prime taking lens thus the need for a second lens to perform the viewfinder task was eliminated. In this design the mirror reflects back (reflex) a perfect duplicate of the exposing image. When the shutter is pressed the mirror springs out of the way, allowing the prime lens to focus on the film or digital chip. After the picture is taken the mirror quickly returns and the viewfinder view is restored. During the exposure the viewfinder view seems to blink. This design called the “single lens reflex” (SLR) was born 1936 by Kine and marked as Exakta.

Now these two designs come in many different frame sizes. Frame size is the size of the image area produced by the camera. The most popular frame size for film is called 35mm. This is because the camera accepts roll film that is 35mm wide. The 35mm film format was first used by Thomas Edison. He selected this size for his newly invented motion picture camera in 1891. That invention caused 35mm to become very popular. In 1924 the first 35mm camera was introduced by Leitz, it could use surplus 35mm movie film. Because movie film needed sprocket holes down both sides to help drive the film through the movie camera, the space for an image was reduced to 24mm height by 36mm width. This format is the grandfather of the term full frame camera which refers to a picture area 24mm by 36mm (a little less than one inch height by a little less than 1 ½ width).

Many modern digital cameras are built around the specifications of a 35mm camera. In a digital camera an electronic imaging chip is substituted for film. The size (image area) of this chip is called the frame size. A full frame is about the same size as the image area of a 35mm film camera.

As technology advances film size and chip size diminish. In the near future full frame cameras will become uncommon.

Alan Marcus (marginal technical gobbledygook)
alanmaxinemarcus@att.net


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9/4/2008 11:34:32 AM

 
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