Schematics Archive (II)

[KA4HJH]

>In my experience, the best scans of schematics have been 1 bit b/w, minimum
>300 dpi, preferrably 600 dpi.  This makes for a compact file, and if you're
>reproducing black line drawings on a white background, typical of most
>schematics, you shouldn't need anything else.

Exactly, only a lot of the stuff I've seen is just as I described (24 bit
RGB). JPEG doesn't get rid of everything. Not only a longer download, but
the first thing I have to do is massage the image so it won't waste all
that space on my hard drive when it's uncompressed.

Another thing I've seen is stuff scanned at 72 DPI! I guess they figured it
would be too big otherwise. Looks like poorly anti-aliased smudgy text with
crappy drawings. Poor contrast, too. Lots of gray along the edges. Again,
they must not have much in the way of software, or no one's ever shown them
the right way.

If this were digital audio it would sound like shit, and you'd be
embarassed to let anyone hear it. But for some reason it's done all the
time. Of course scanning is a time consuming pain in the ass. But I
wouldn't do it unless I had the time and desire to do it right. I wouldn't
want my name on something that wasn't done right.

BTW, I've seen problems with PDF files, including those done by list
members. These are much more technical, harder to spot, and sometimes
involve cross-platform issues. I haven't gotten around to saying anything
to anybody yet. A lot of the blame can be placed on Adobe and the whole
font-embedding scheme.

>OTOH, If you scan a pcb layout, and the layout shows multiple layers, or
>component placment along with the traces, etc, then 8 bit gray scale works
>good.

I've had problems getting Acrobat 3.01 to accept 4 bit TIFF's. I sort-of
got aroud it by taking the 8 bit grayscale image and quantitizing the
palette to only 16 grays (you can do this in Debabelizer). Now the image
will compress almost as small as a 4 bit image, and Acrobat is happy.

I don't know everything, just what I don't like.

Terry Bowman, KA4HJH
"The Mac Doctor"