Re: B&W IE

[George L Smyth <GLSmyth@xxxxxxx>]

Murray White wrote:

>  Assuming that you are using Kodak IR, meter
> >at EI250 through a #25 filter then open up 3-4 stops (that's what I
> >do).
>         Really?? Boy this gets "confusedor & confusedor".  Someone says EI
> 250, someone says ISO 200. Some say use the filter on the lens before
> metering, some say meter, open up for filter factor and add the filter. I
> really can't understand why one would meter through the filter and then open
> up more. Wouldn't it also be easier to assign an ISO  to the film, use
> either reflected or incident meter reading and state which and if reflected
> is being done from a gray card and then apply the filter factor for the
> amount of additional exposure required?

It sounds like you're starting to get the idea. <g>  The bottom line is
that many people use this film in many different ways.  I can point you
to my Web page at "Rest Gently" (in the South Wing) as an example of an
image that was shot using EI250, and "House Of Dreams" (in the North
Wing) as an example of one shot at EI100.  This is very versatile film.

I meter TTF (through the filter) because I've always done it and it
makes sense to me (I know of others who use a handheld meter without a
filter - we all have our ways).  I use a #25 filter because it gives the
meter a closer approximation of the light that will eventually strike
the film.  As meters generally are not calibrated for infrared
radiation, placing an opaque filter over the meter would render
unmeaningful and incorrect information.  I've "generally" found there to
be a 2 stop difference between my Hoya R72 filter and a #25 filter, so
it makes sense to me to meter the most meaningful information available,
then compensate for the filter that's actually used.  I say "generally"
for the reason mentioned below.

An ISO rating would not be meaningful for this film because it is
sensitized to respond to infrared radiation.  As this type of light is
variable and is not reliably measured with your filter, there is no way
to properly rate the film.  As a matter of fact, when I suggest to
people that they use EI250 as a starting point, I actually modify my
personal EI as determined by the time of day, time of year, weather
conditions, etc.  For the effects most people are looking for, EI250
will get them in the ballpark.

Also remember that the developer you use and the way you develop your
film will affect the film speed.  Someone suggesting EI200 may be
looking for exactly the same thing I am, but their development may be
different.  The bottom line is to do your own testing.  I know that it's
boring, but a full weekend of work will give you enough information to
be able to get the most this film has to offer.  If you'd like, I can
elaborate on that, or you can just shoot and adjust.  Either method
works.

george

-- 
 Handmade Photographic Images     
  http://www2.ari.net/glsmyth

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Topic No. 17