scanimage vs. xsane on linux (file formats)

[Charles T Smith]

I'd like to use scanimage to scan, but the final print-out is about 10%
smaller than the original. If I use xsane (version 0.995), it comes out
correctly sized.

If I save the output from xsane, I get the following file:
i20090628-0002.png PNG 2400x3472 2400x3472+0+0 PseudoClass 2c 8-bit
19.2695kb 0.280u 0:02

I've tried lots of variations with scanimage and convert:
efe1-2.pnm PNM 848x1169 848x1169+0+0 DirectClass 16-bit 5.67237mb 0.300u
0:02
efe1.png[1] PNG 848x1169 848x1169+0+0 DirectClass 16-bit 3.45026mb
efe1.pnm[2] PNM 848x1169 848x1169+0+0 DirectClass 8-bit 2.8362mb
efe1.tiff[3] TIFF 848x1169 848x1169+0+0 DirectClass 8-bit 2.8364mb
efe1r.pnm[4] PNM 848x1169 848x1169+0+0 DirectClass 8-bit 2.8362mb
efe2.pnm[5] PNM 2544x3508 2544x3508+0+0 DirectClass 8-bit 25.5328mb
2.560u 0:04

I saw someone on the net somewhere say something about using -type
Palette with convert, but that didn't help.

If I add the Resolution parameter to scanimage, setting it to 300, my
image becomes huge, printing out on 9 pages!

Isn't the original document size stored with the scanned image? How can
I ensure that an A4 document is always printed out as exactly A4 format?

TIA,