Re: Exposure (was: Rangefinder etc)

[boblong@xxxxxxxxxxx (Robert Long)]

On Thu, 18 Jul 1996 11:01:55 +0200, you wrote:

|On 18 Jul 96 at 1:52, Vaughan Bromfield wrote:
|
|> Kodak's data suggests ISO 80 for HIE. This refers to a hand-held meter, and
|> assumes a red or ir filter is on the camera lens. That is, don't add any
|> filter factor corrections to the ISO 80 reading!
|> 
|> For real-time SLR TTL metering, set the meter to 300 - 400 ISO with a red
|> filter. Or set the camera to 80 ISO and set the shutter/aperture without a
|> filter, then screw on the filter and expose.
|
|My favorite way of explaining exposure is indeed starting with this 
|400 ASA. Then adjust +3 stops for red, +4 for 87 and darker, and +5 
|for 87C.
|In the past several people have emailed me asking for the proper
|setting for the darker colors 87B and 87A. Regrettably, Kodak has
|skipped many of its IR colors (only 87 & 87C remaining I believe),
|so I am currently involved in a (too) long project having this color
|made in resin.
|
|But I noticed from at least one bio that a 87B user is among 
|us....perhaps you could tell us the typical exposure for this filter?
|Would be very convenient if one could just add another stop, so +6 
|for 87B, and +7 for 87A. But the curve of the film's sensitivity 
|should tell me otherwise....it wouldn't surprise me if it is +8 and 
|+10....
|
|BTW, anyone numbers on Konica with darker filters than #25?
|I once read that for practical purposes (read: not yet bulb setting) 
|#89B was the darkest usable color; but I also read about using #87, 
|ending up with fractions of ASA....;-))

I'm having a lot of trouble reconciling any of this with what I read
in the instructions packed with my current roll of HIE.  The roll was
purchased recently but the sheet's revision date is 7-83.  Is that
really current?

The sheet specifically says that the ISO 80 speed is for use *without*
a filter and that if you are using the recommended Wratten 25 filter
you should set the meter for ISO 50.  That is less than a 1 stop
difference, but of course the Wratten 25 presumably passes the entire
IR band with little attenuation, so it would only be visible
wavelengths that would suffer the usual filter factor.

Again, in giving recommended settings without a meter, the sheet shows
a 1-stop difference between the Wratten 25 setting (1/125 at f/11) and
that for no filter (1/125 at f/16).  This doesn't sound like ISO 400.