[pdftex] png including and scaling magic(?)

[franciszek holop]

hello,

this is my first post here, so first a really fast big fat thank you for
this great program.

i use pdflatex for creating computer manuals and i do include png
pictures of various windows.

by experimenting, i have found out that scaling all the png's by the
factor of 0.68 gives very nice pictures (by that i mean natural sized
pictures, just as when captured) on the screen at particular zoom levels
in gv(2.0, natural size) and in acrobat(147% - almost 150%).  all the
pictures are 72dpi, and they are added with the
\includegraphics[scale=0.68]{picture.png} command.

i was wondering why is this, and whether this 0.68 is a magic number or
what.  haven't seen in any faq or posts.

please enlighten me, and i am curious what other people use when
interested more in reading the docs from screen, as printed text
as always cool.

-f
-- 
i am so open-minded my brain falls out.