On Apr 20, 23:53, John Allain wrote:
[ Pete wrote ]
> > Hi-res 35mm is probably better than that. Kodachrome certainly
> > is; it can resolve a couple of thousand lines per *millimeter*
under
> > ideal conditions.
>
> Can this be backed up with published information?
Good question.
I can't find any actual figures on Kodak's website. The figure I used
is one I saw in a couple of places on the web, and in some old notes
(see LP Clerc, Photography: Theory & Practice, sec.349). I used to be
really into photography, and about 30 years ago, and I did a 3-year HND
course which included a lot of theory.
I've seen references to about 1/10th or even 1/20th of that in various
places, too. That seems too low, but there could be several reasons
for that. Firstly, it used to be the case that only Kodak would
process Kodachrome -- one of the reasons professionals used to use it
only for special purposes, preferring Ektachrome because it could be
processed locally (and therefore quicker, and with "adjustments").
That's no longer the case, but I don't know if Kodak have changed the
process (quite likely) or just made it available to other processors.
I do know that professionals could get a different service from Kodak
than normal users (because I could, via the college I studied at) and
that could make a big difference to the results. We used to reckon a
35mm Kodachrome slide roughly comparable to a 6x6cm Ektachrome. Not
that Ektachrome's at all poor: want a good colour print? Take an
Ektachrome slide and make a Cibachrome print. Except I don't think you
can get Cibachrome any more.
The low figures I've seen for Kodachrome have been on pages where it's
compared to other colour films, and I think they're suspect, because I
don't think they're the result of optimal (or even close) conditions.
I'd be prepared to believe that 2000 lines/mm is a theoretical figure
based on grain size. If so, that won't be the true figure for a real
exposure in a real camera, so I'd take it with a pinch of salt. A
"good" lens on a 35mm camera typically has a resolving power no better
than 150-200 lines/mm (ref LP Clerc again, and MJ Langford, Advanced
Photography).
--
Pete Peter Turnbull
Network Manager
University of York
Received on Wed Apr 21 2004 - 13:01:39 BST