From: CCGM@MUSICM.MCGILL.CA (CCGM000)
Newsgroups: rec.photo
Subject: Re: Different Films and Pro rated speeds ?
Date: 14 Sep 92 14:31:08 GMT
Organization: McGill University Systems Inc (MUSIC/SP)

In article <470@cimsand.UUCP> rune@cimsand.UUCP (Rune Riisnaes) writes:
>drinkard@icelan.enet.dec.com (Rich Drinkard) writes:
>:
>: Does a list exist anywhere of the different (common anyway) films and the ISO
>: ratings the pro's use to shoot with them.
>
>Seriously, this probably depends on a number of things, like personal
>preference, your subject, the development process at your lab, your printing
>process, etc.

   I agree wholeheartedly. I might add that this provides you with an
opportunity to test and experiment and find out what you like best.
As well, it might be a good idea not to work from a "list of films"
but rather to pick several and learn what works well for you with
them. For example, I rate my B+W films at EI 80, so that when I process
and print from them I get the results that I expect. At 100 they'd
be too thin for MY setup - perhaps not for yours.
>
>An interesting question:  Most photographers I know, prefer to shoot Velvia
>at a lower ISO than rated.  If this is a common trend, what are the criterias
>Fuji (and Kodak for that matter) uses to determine a films rating.
>Is it purely technical, like density, color saturation, and such ?

   As I understand it, it's supposed to be technical - there's an
ANSII standard for film speed determination! However, it's also related
to the manner in which the film is processed - that's why I was so
interested a while back to hear of the different manner in which
Fuji and Kodak processed slide film. Some people consistently rate
Velvia lower than 50, while others find that 50 is just fine.

   But ... one has to be careful with film speeds on boxes. For
example, T-Max P3200 - fast film at ISO 3200, right? Wrong. In fact,
it's rated at 1600 and to get to 3200 you're expected to push process
it. That's the "P" in the name: Push-3200. Ektar 1600 is only a nominal
rating - I believe (could be wrong) that it is actually rated at 1000.
   Since these are print films anyway, minor differences in ratings
can be easily overcome by the lab correcting the density in the
printing process. So Kodak's flip from 125 to 100 with Ektar isn't
necessarily a change in the film, or ONLY a change in the film. Had
125 caught on big, even with a revised emulsion Kodak could easily
have retained the 125 moniker. But ... I suspect that they found via
market research that folks believed that 100 rated films gave finer
grain than 125 rated films (namely, Ektar 125). (Although it is quite
reasonable to accept that the emulsion changed as well.)
>
>When Kodak changed the ratings of its Ektar film from 125 to 100, was
>that caused by a change in the film itself, or as a result of the way it
>was being used ?
>Does anyone know ?

   I confess that I haven't inside info, and that what is above is
(mostly) opinion. But do keep in mind that materials DO differ, and
that it is up to the user to determine best use. Even without this,
however, the "system" is set up for the average user such that without
exercising any massive amount of judgement, things will still work
out. (Sort of like the slogan, "You press the button, we do the rest"!)

Glen Matthews
MUSIC Product Group, McGill University
550 Sherbrooke St. West, Montreal, Quebec, Canada H3A 3C5
Phone: (514) 398-4477 Fax: (514) 398-4488 BitNet: CCGM@MCGILLM
Internet: ccgm@musicm.mcgill.ca   Anonymous FTP: vm.mpg.mcgill.ca