Shel,
There was a guy that posted the technical details on rec.photo
(prob. medium-format, or large-format group as that is where I
use to lurk) in reply to my post about this two, three years
back. The change was supposedly based on some refinements in
measuring technology worked out just before W.W.II.
I was very much into photography back in 59 when the speeds were
changed. At that time it was claimed that the safety factor was
no longer needed as most adjustable cameras by then had meters.
It was also supposed to speed up printing with the then new
automatic printers due to the thinner negatives.
I have here before me a Kodak Data Guide for 1956, Tri X is
rated 200, Plus X 80, and Panatomic X 25. The current speeds
were adopted as I said in 1959 with no changes in emulsions at
that time.
As for the higher speeds since then (mostly color films), I
believe they are are a result of genuine improvements as the
same rating technique is used today as adopted in 1959. There
have also been immense improvement in quality of almost all
films since 1959.
The change applied to all negative films (color and B&W), but
not to slide films because slide films never had the safety
factor applied to them, they didn't have enough latitude. Some
films did not go up exactly one stop, Tri X sheet film only went
to 320 for example.
And, no, there has not been another change in how film speed is
rated since then, as far as I know. The change to ISO was only
an adoption of both ASA and DIN ratings to ISO. ISO = ASA/DIN.
--Tom
Shel Belinkoff wrote:
>
> Tom Rittenhouse wrote:
>
> > One of the problems w sunny-16 is
> > that when it was the way to meter
> > film speed was rated one stop lower
> > than it is today. No they didn't
> > improve the film, they just changed
> > the rating. The difference is that
> > before meters were common the film
> > makers had a one-stop safety factor
> > in the film speed. That allowed the
> > film to be over-exposed one stop, or
> > under-exposed two stops and still get
> > a printable negative. Modern negative
> > film has a wider range than that so
> > sunny-16 is usually close enough. If
> > you are interested this change took
> > place in 1959, we photographers do
> > like to keep up to date <f>.
>
> Hi Tom ...
>
> I don't doubt you, but I tend to. Far be it for me to challenge the
> veracity of your comments, for I'm far from well-versed in these
> matters. However, I am somewhat skeptical, so perhaps you'd care to
> expand upon this point a little.
>
> Tell me exactly how the film rating was changed. Was it arbitrary?
> Did it take into account the film's latitude? Is this true for color
> negative film as well as B&W negative? If the actual film speed is
> the same, then what you're saying is that film makers are just making
> their emulsions faster by rating the film at a higher point within
> it's latitude. However, if the film speed is the same, then there's
> still only one "correct" exposure in order to garner the best results
> from the negative, and that would be the old speed rating, since, as
> you say, it's not been changed.
>
> Further, today there are very few emulsions that were available back
> when this change was supposed to have occurred, and, of those that are
> using the same name have been "improved" (i.e., changed) many times
> over. How would you use then "sunny 16" rule with a new emulsion, one
> that hasn't had its speed rating modified?
>
> Finally, you mention that this change took place in 1959, and you also
> noted that "The difference is that before meters were common the film
> makers had a one-stop safety factor in the film speed." These
> statements seem somewhat at odds with one another, since meters were
> quite common before 1959 and TTL meters didn't appear until after
> 1959, with some possible exceptions.
>
> So, perhaps you can explain this concept a little more for, being the
> mental midget that I am, I'm having a hard time fully understanding
> the concept.
>
> --
> Shel Belinkoff
> mailto:[EMAIL PROTECTED]
> "Why should I use a meter? What if the darn thing broke on me
> when I was out making a photograph? Then what would I do?"
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--
Tom "Graywolf" Rittenhouse
Graywolf Photo, Charlotte, NC, USA
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