Re: more ir now?

[filje@xxxxxxxx (p geller)]

>: Andrew Davidhazy < said


>..... Therefore, the only varialble is the amount of atmosphere the
energy
>emitted by the sun has to go through to get to the ground here on Earth.
>>goes up and so the color of the light is more reddish ... and
presumably
>therefore also the _ratio_ of IR to visible also is greater. But the
total
>amount in my opinion can not be any greater than what the ratio
naturally is as
>it leaves the Sun.

I would agree. the light emitted is relatively constant. 
  But is the ratio of  IR proportional to the color temp. 

>Anyway, the _density_ that film produces is a function not only of the
actual
>amount of energy present or available but also the exposure time. This
is the
>basis for the "exposure" formula = Exposure being equal to the
Illuminance
>times the Time.

Yes , I was not clear about this.
 If one uses a lightmeter not an IR meter to measure illumination and
makes an exposure with the  Exposure Index that has previously yielded a
negative (assuming development and other user variables remain constant)
of a given density.....
wouldn't  your EI need to be adjusted upward?

It seems like a  reasonable assumption given that the instructions with
HIE give an
IE of 125 for tungsten light and only 50 for daylight. 


All my sensitive light meters have IR attenuation filters but they seem
to be able to meter some IR just the same through 87 and 89b filters.
Next sunny day (it may be a while) I think I will compare  IR filtered
and 
unfiltered readings  at noon and in the late afternoon. 



Phil
Phillip Geller Photography

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