RE: 87c, Red 25, and one more...

["George L Smyth" <GLSmyth@xxxxxxx>]

> -----Original Message-----
> From: owner-infrared@xxxxx [mailto:owner-infrared@xxxxx]On Behalf Of
> Luvdove6@xxxxxxx
> Sent: Friday, October 29, 1999 3:18 AM
> To: infrared@xxxxx
> Subject: Re: 87c, Red 25, and one more...
>
> > Anyway, if you shoot two rolls of film at different speeds then you
> >  definitely need to adjust the development times, so no, you can't do
them
> >  at the same time (unless you are just testing).
>
> I'm still really new at all this so I still don't get how this part
works...
> if you have two rolls you shot... one at say, 50 and one at 200 and you
> metered everything.... one of the factors of exposing the film is
> definitely ASA (EI I guess is always what you'd say for HIE) so the meter
is
> considering the light in the scene, your settings like aperture and
shutter
> speed, and the ASA of the film...  so I still don't see how EXPOSURE is
> different if you use the meter since it would change shutter speed
suggestion(on
> manual) to the ASA speed you set it on.... so how are they exposed
differently?
> Konica says that you should shoot HSI at ASA 12 with red 25 and ASA 32
> without a filter... so sometimes in ONE ROLL I'll switch back and forth
> depending on if I want the result to be like regular b&w (like if
> I'm inside or whatever) and when I develop the roll it all comes out even
> (or seems to, to me)...  do you see why I'm lost?  I know there is a
difference
> but don't understand why  ;-)

(Konica does not make HSI, that's Kodak.)
If you shoot film at different "effective" speeds, then the development
times will always need to be different.  However, it sounds like you are
confusing metering through the filter and without the filter.  When you do
this, and take the filter factor into consideration, the "calculated" speed
will be different but the "effective" speed will be the same.

Try this.  Put a #25 filter on your camera and set it to manual.  Adjust the
settings so that you will correctly expose a particular scene.  Now remove
the filter and reexamine that same scene.  As you can see, if you release
the shutter now, you will overexpose the negative.  Since the filter absorbs
some of the light, the same amount of light will not reach the negative with
it inserted as without.  The number of stops of light that is lost is called
the filter factor.

So when you expose your film, you can either meter the scene through the
filter, or meter without the filter, apply the filter factor in your
settings, then shoot.  The latter is most commonly done when you have a
meter that is not within the camera (like a view camera).  So, as you can
see, the metered speed will be different, as determined whether or not you
are metering through the filter.  This is why I always try to explain that
my typical speed of EI 250 for HIE/HSI comes about when metering through the
filter (I also note this when offering developing times, as it makes a
difference).

Personally, I always meter through the filter, whether I use my 35mm cameras
or my view camera.  I don't see much sense measuring light that will not
strike the film.  However, others have reported that it is better for them
to meter without the filter.  The bottom line is that whatever works best
for you is what you should follow.

george

---
Handmade Photographic Images
http://www2.ari.net/glsmyth/

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