Olympus-OM
[Top] [All Lists]

[OM] Re: ( OM ) scanning and digital resolution

Subject: [OM] Re: ( OM ) scanning and digital resolution
From: Jim Brokaw <jbrokaw@xxxxxxxx>
Date: Fri, 30 Jul 2004 21:07:14 -0700
on 7/30/04 5:13 PM, Brian Swale at bj@xxxxxxxxxxxxxxx wrote:

> He just told me about one aspect of the images he needs, as follows:
> "no less than 300 dpi"
> 
> My question is, how do I relate this to pixels, when scanning.
> 
> Does one "d" as in "dpi" = 1 pixel?
> 
> If not, what does it actually equate to?
> 
> Sincerely,
> 
> Brian Swale

Brian - This can get very complicated... Basically, the B&W printing uses
what are called 'line screens' which translate at some level to 'dpi', but
not directly like you might expect. The is because photographic images
commercially printed are done using a process called 'half-tone' printing
(there are other processes, but typically used only for high-end art books,
as they are much more expensive.) If you scan your images at the highest
resolution you can (optical resolution, best using a film scanner) that will
give you the most to start with. Then you need to consider the final size of
the image on the book page... and you work out to some good ratio between
pixels, line screen, and image size. A high-quality half-tone image printed
on good coated paper (the shiny stuff) can look almost like a photographic
(or good inkjet) print. For half-toning, the smoothness and number of grays
in the print is related to the line-screen number, the bigger the number,
the more grays and smoother image you get. A good commercial printer should
be able to explain this more exactly, or you can find a tutorial on the web
I'm sure. By the way, when you deliver your images, you just need to send
them the high-resolution scanned images. The printer will use what is called
an "image-setter' to output the files. The imagesetter is like a very high
resolution laser printer that outputs to film, creating a negative that is
photo-etched onto the printing plate. For this output, Photoshop files are
fine usually, but don't use JPEG or other compressed files. Send TIFF or PSD
files, check with the printer first about their preferences. You should get
proofs, either separate from the page proof, or incorporated into the page
proofs. Check these to make sure the image looks like you expect, or have
the printer go around again on it. I used to purchase printing services for
our advertisements and catalogs, and its fascinating... much different from
photography, but somehow still similar.
-- 

Jim Brokaw
OM-'s of all sorts, and no OM-oney...




==============================================
List usage info:     http://www.zuikoholic.com
List nannies:        olympusadmin@xxxxxxxxxx
==============================================

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz