From: Les Newcomer (lnphoto@ismi.net)
Date: 02/11/00-04:40:36 PM Z
When I typed this it was a fairly nice table, now it looks like garbage.
Sorry.
Les
Les Newcomer wrote:
> Roger,
>
> There is a book called the "Handbook of Photography, it was published in
> 1939 and it can take just about any simple question and turn it into an
> incredibly accurate jumble of mathmatical formulas that will take you a
> week to under stand. For expample:
> "The various film-speed systems are not based on the same fundamental
> use of the D-log E curve (they changed it to Dlog H curve later), and
> the film-speed numnbers do not progess uniformly in the various systems;
> in some cases the speed number progress proportionaltely to the relative
> speed, in others they do no. It is possible, however, to devise a
> relationship between the various film-speed numbers, as given in
> Appendix B, altohough such relations are to be regarded as being, at
> best, rough approximations. If Sa is some arbitrary or relative
> silm-speed or film -sensitivity number and Sn is the film speed or
> sinsitivity in the 'n' system of rating, then the various film -speed
> numbers will be related to the relative sensitivity by the equations
> given in Table I."
>
> Film-speed system Film
> speed symbol Film speed
> related to relative film speed, Sa
> Weston
> Sb
> Sb=.223 Sa
> American H and D (k=10)
> Sc
> Sc=5.8 Sa
> European Hand D
> Sd
> Sd=27 Sa
> Watkins
> Se
> Se=10.65 Sa
> Wynne
> Sf
> Sf=10.9 (square rt of) Sa
> Burroughs-Wellcome
> Sg
> Sg=2.83/Sa
> American Scheiner
> Sh
> Sh=(1+9.5 log10 Sa)
> European
> Scheiner
> Si
> Si= (5+9.5 log10 Sa)
> Eder
> Hecht
> Sj
> Sj=(43+24 log10 Sa)
> DIN
> Sk
> Sk=[(10 log10 Sa) -7] /10
> Eastman*
> Sl
> Sl=1.165 Sa
>
> "* The film-speed values for the Eastman Kodak Co. minimum-gradient
> film-speed system are based on published data for aonly a few emulsions,
> from which it was determined that the Kodak numbers are approximately
> five time the Westion Speed numbers for the same emulsion."
>
> Sa is any number you want to come up with. Appendix B is a table that
> lists Sa as 'relative speed values" much like that of Iso numbers today
> except they start with 1 and then play out the values for all of the
> systems listed above except for Kodak. I've repeated the table and
> replaced the "film speed symbol" with the value equal to 100 on the
> relatve speed column
>
> Film-speed system Film
> speed symbol Film speed
> related to relative film speed, Sa
> Weston
> 23.3
> Sb=.223 Sa
> American H and D (k=10)
> 580
> Sc=5.8 Sa
> European Hand D
> 2700
> Sd=27 Sa
> Watkins
> 1070
> Se=10.65 Sa
> Wynne
> F/209
> Sf=10.9 (square rt of) Sa
> Burroughs-Wellcome
> 0.028
> Sg=2.83/Sa
> American Scheiner
> 20.0
> Sh=(1+9.5 log10 Sa)
> European Scheiner
> 25.0
> Si= (5+9.5 log10 Sa)
> Eder
> Hecht
> 92
> Sj=(43+24 log10 Sa)
> DIN
> 13/10
> Sk=[(10 log10 Sa) -7] /10
> Eastman*
> 116.5*
> Sl=1.165 Sa
>
> I've found if you print theis out and sleep with it under your pillow it
> really does help understanding it.
>
> Les
>
> > Hi!
> > I was wondering if anyone knows just when we began to
> > use ASA numbers? I was looking at 1939-1950 magazine
> > ads for Ansco and Kodak sensitive materials and the
> > the lack of speed information is, well, noticeable.
> >
> > Any one know of a chart listing the equivalent speeds
> > for the former H&D speeds with the ISO (or ASA)
> > speeds?
> >
> > Thanks... and sorry about the off topic(?)subject, but
> > the recent inquires of that um... commercial entity
> > just seemed to open this can of worms...that stuff
> > about international standards of light and...well if
> > you have any information, use your own discretion as
> > to whether it should go on or off list. Thanks.
> >
> > Ray
> > __________________________________________________
> > Do You Yahoo!?
> > Talk to your friends online with Yahoo! Messenger.
> > http://im.yahoo.com
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