Re: Reciprocity Problem

> I would like to enter in a meter reading, and have it give methe number of
> seconds (or minutes) for the exposure with all filter factors and
> reciprocity factors adjusted in. Factoring filters is easy, but I am hung
> up on reciprocity.

If you don't "eyeball" your exposures, which I could bet you don't do, just
take your meter readings through the filter, that way the uncorrected
exposure already includes the filter factor. Remember that filter factors
are just a guide, different scenes with differente predominant colors would
be affected differently by a filter.

> From the responses I have received, it appears that I need to do some sort
> of nonlinear regression curve. I did some quick research on the net for
> information on that, I quickly became bewildered with alot of information.
> I might be biting off more than I can chew!

 Don't think so, if you download Regression Analyzer
http://www.zdnet.com/downloads/stories/info/0,,000QE3,.html you just need to
input any pair of values of KNOWN reciprocity corrections (Y axis)
corresponding to METERED values (X axis), select a Regression Analysis
method (I suggest 2nd or 3rd Polynomial) and magically the program draws the
graph and tell you the algebraic equation. IT REALLY SOUND MORE COMPLICATED
THAN IT IS, the fact is that you don't even have the remote idea on how it
is done.

> I am not sure if this can
> definately be constructed with the program I am using or not. Obviously
> an outside program might not be to helpful, as I am trying to get exposure
> information "on the fly" in the field.

The OUTSIDE program will be used ONLY to get the equation that describes the
reciprocity corrections of your film. Having the equation, you use it with
your MATHPAD to calculate ON THE FLY any reciprocity corrections for a given
metered exposure time. You could even print the GRAPH the Regression
Analyzer gives you and use it as a back up in case your PDA fails.

Guillermo
Received on Tue Jun 19 17:15:59 2001