[sane-devel] How to accurately scan A4(210mmx297mm) size paper?

[hh.eu at gmx.de]

Am 27.06.2008 um 07:26 schrieb eagleskycloud:

> But is DIN A3  same  to  A3? Is DIN A4  same  to  A4?Is DIN A5   
> same  to  A5?
>
> DIN is standard  of  Germany.Is the size of  DIN A3 is 297mm x  
> 420mm? Is the size of DIN A4 is 210mm x 297mm?

Yes, they are basically the same. The A series was first standardised  
as DIN 476 in Germany in 1922, was widely accepted in other countries  
later and then, around the 1970s, standadised internationally as EN  
ISO 216.

The success is based on the good geometric properties: A0 has a size  
of 1 m^2 and a ratio of (approximately) 2^0,5=sqrt(2) (larger to  
smaller side), and from there you get each smaller format [A1 from  
A0, A2 from A1, ...] by halving the larger one parallel to the short  
side, and the ratio of the sides always remains the same.

However, DIN 476 demands tighter tolerances:

+/- 1,0 mm (for dimensions up to 150 mm),
+/- 1,5 mm (for dimensions from 150 mm to 600 mm),

whereas ISO allows 1,5 mm and 2,0 mm, respectively.

So some rounding is acceptable. But you are right, you should try to  
get the paper size as precisely as possible from the scanner.

See <http://en.wikipedia.org/wiki/Paper_size> for details, its all  
well described there.

HTH
-M