Re: Autoexposure Follies?

[Joshua_Putnam <josh@xxxxxxxxxxxx>]

Pico <Pico@xxxxxxxxxxxxxxxxxxxx> writes:

>From: Theo Benson <TBenson@xxxxxxxxxxxxx>

>>I used to have a Weston Master. Great meter but I had to carry around a
>>Weston-to-ASA (ISO to everyone else) conversion scale. I'm going to run a
>>test using my Gossen spot meter and filter as suggested earlier to see what
>>happens.

>I was referring to the Weston Master light meters intended for photography.
>Apparently you have a scientific meter. You can get a Weston Master for
>about $25, just about anywhere.

He probably had one of the older Weston Master-series meters
that's calibrated in Weston film speeds, which aren't the same
as ISO/ASA film speeds.  But the conversion isn't difficult
enough to need a table -- find your ASA speed on the emulsion
speed dial, then go to the next slower setting, e.g. ASA/50 =
Weston 40.  At least for every film speed I ever used, this
method matches the values in the Weston/ASA conversion table in
my old CRC Handbook of Chemistry and Physics.

For IR, of course, you aren't trying to convert from one speed to
another, just find a reasonable setting, so you can start with a
known good exposure and adjust the speed until the meter matches
the known exposure.  

*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************

------------------------------