RE: Exposure for 87C

[ANDPPH@xxxxxxxxxxxxxxxxxx]

>Completed second roll of Kodak HIE 135 using an 87C filter mounted behind
>the shutter of SLR.  Exposed at ISO of 50 this time and developed in D-19
>(no filter factor considered).  Results are beautiful. According to Kodak
>the film should have been rated at ISO 10.  I do wonder where Kodak gets its
>recommendations.

ooops ... forgot who sent this - but anyway ... If you used an ISO of 50 that
meant you were in fact using a filter factor. A filter factor menas that you
use a greater exposure to expose the material than if no filter were placed
over the lens (or in front of the film somewhere).

Filter factors are affected by many things. Some right off the bat are
development conditions and subject reflectance of the wavelengths passed by the
filter and in this case the ratio of IR to visible in the scene plus the
spectral sensitivity of the meter. They also depend on what _you_ consider 
a good negative.

The difference between an EI of 10 and one of 50 is actually not that great
although with a contrasty film like HIE it is a significant difference. For
what it is worth, I personally think that Kodak has done a very good job in
terms of characterizing the sensitometric qualities of HIE (as well as all
their other products). 

Just for the record I have no affiliation with Kodak. I use Kodak products as
well as that of other manufacturers. I do have Kodak friends.

Andy

 o o  0 0 o   o  Andrew Davidhazy, Imaging and Photo Tech - High Speed Photo
  \/\/\/\/\/\/   andpph@xxxxxxx,  http://www.rit.edu/~andpph,   716-475-2592  
___|        |_______________________________________________________________
                 PhotoTech Department:   http://www.rit.edu/~andpph/ipt.html
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