When you reach the stage where you produce files that need to be printed,
they need to be in CMYK. What tends to happen is that the yellow page
adverts are very very specific on what colours can be used and how much
yellow to use (they print the yellow onto white paper). If JPG images are
given to a graphic designer, it has to be converted into CMYK (usually with
C as 0, M around 5 Y around 30 and then the black plate holds the picture).
As has been pointed out, JPG can't hold vector infomation but more
importantly it's not a file type that the printers can actually use to
create the CMYK plates - the EPS however does contain the seperation
details. Another point is that if you wanted to reach the same quality as
vector on a printed press for text, you'd have to have *huge* images (300dpi
is the usual for photos but text is printed to well over 1000dpi). Another
reason is that JPG is a *lossy* compression - you lose detail. For
instance, if you look closely at text on in a jpg you'd notice wierd noise
which is created by the JPEG compression.
Hope this answers your question,
Cheers
Alan Bloom
>> Stay informed about: EPS vs JPG