From: Eric Muller (emuller@adobe.com)
Date: Wed May 18 2005 - 09:05:12 CDT
Patrick Andries wrote:
> A4, I believe, is German (DIN) in origin before being an international
> standard (ISO). It is I believe a pure coincidence that the foot and
> the length A4 are approximatively equal since the base of the ISO A
> paper size series is the A0 format whose area is 1 m². By successive
> division respecting the ratio of √2, you get A4 to be 297mm × 210 mm.
>
The motivation for the sqrt(2) ratio: if you fold a piece of A<n> paper
in two, you get exactly an A<n+1> piece. Thus you can print two A4
pieces side by side on an A3 piece, without margins. If you scale up an
A4 piece, you can fit precisely an A3 piece, without margins (and
conversely). Combine the two, and you can print two A4 pieces side by
side, scaled down, on one A4 piece, without margins. Very convenient.
The motivation for one of the A<n> = 1 square meter: the metric system.
The motivation for the actual dimensions: given the constraints above,
297 x 210 is close to 270 x 210, the previously used common size (at
least in France). I don't know where that older standard comes from.
Eric.
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