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Old September 27th, 2011, 11:50 AM
Doug Kerr Doug Kerr is offline
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Join Date: May 2006
Location: Alamogordo, New Mexico, USA
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Default The "APS-H" frame size

I was asked recently why the frame size used by the Canon EOS !D series cameras is called "APS-H".

My reply began, "not by me, it isn't."

But here's the story.

"APS-H" describes one of the three delivery crops (my term) which the user may choose for printing an image taken on APS (Advanced Photo System) film.

The APS-H frame is 30.2 mm x 16.7 mm.

The frame size of the Canon EOS 1D series cameras (so far) is in the general range of 28.7 mm x 19.1 mm.

Not a very good fit? Hey, I didn't start doing that. It's at least as good as "ten-gallon hat".

Whence the "H"? That is evocative of "HDTV", a paradigm that was coming over the horizon when the APS system was introduced, and recognizes the "wide" aspect ratio of that crop (which is 1.808:1). The referenced HDTV format has an aspect ratio of 1.780:1 (16:9).

If we spoke of a frame size as being "APS" (no suffix) what would that mean? That refers to the full APS frame (the taken frame size). That is 30.2 mm x 16.7 mm in size. (That is, the "-H" delivery crop is no crop at all, but rather is full frame.)

Just to finish the story, the APS-C delivery crop has dimensions of 25.1 mm x 16.7 mm (an aspect ratio of 1.503:1). "APS-C" is used ("not by me") to refer to a range of digital camera sensor sizes; it is applied, for example, to the frame size of the Canon EOS 40D, which is 22.2 mm x 14.8 mm, and to slightly larger or smaller frame sizes offered by other manufacturers.

The "C" is evocative of "classic", and refers to the aspect ratio being very near that of a full-frame 35-mm film camera (1.500:1).

The APS-P delivery crop ("panoramic") has dimensions of 30.2 mm x 9.5 mm (an aspect ratio of 3.179:1)

Best regards,

Doug
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