Joining in and GN flash/filter question

[Eric Pederson <epederso@xxxxxxxxxxxxxxxxxxxx>]

Greetings!

I am new to IR photography and I'm just now joining the list, having
already read (perhaps sporadically)  through the FAQ and much of the
mailing list archive.  I'll start with my question and then provide bio
information as suggested in my welcoming email. 

Question:
Assuming comparably calculated guide numbers across flashes, can I assume
comparable IR output? 

I have several flashes and am interested in playing with a visible light
opaque filter in front of the flash. I'll need to make a series of test
shots, but what I would like to be able to assume is that if I make a
series of test shots with a particular filter/film combo on a particular
flash, that I could use that exposure information for any other flash as
well -- making the appropriate GN calculations and shooting on manual, of
course. Also, for the same flash in different zoomed head positions, can I
assume that the IR reflectance within the zoom head will be comparable to
the indicated visible light reflectance and thus I would only need to
make tests in a single position?

Bio:
- Name: Eric Pederson

- Profession/Study: Professor, Linguistics

- Country: USA

- Personal history of photography: Very amateur, starting in mid 1970's.

- Preferred subjects: mostly travel snapshots in earlier years,
now mostly my kids. Landscape and portrait when time allows.

- Format (35mm/medium format/large format): 35mm (mostly Olympus OM) and
LF (4x5", Tachihara/Schneider 150mm) 

- Materials (film, filters, paper, chemistry): Mostly b/w these days. 
Mostly TMax100/400 and mostly Kodak paper/chemestry (Polymax, Xtol,
...). Attracted to MACO sheet film since HSI (which I've only used once)
has been discontinued. I would like to get to know the same film in both
formats as a beginning. 

- Other strange hobbies: When I was younger and without kids..... :-)

- How did you find out about this list: Web link through the Bronica pages (I
think).

- Expand on anything photographic you like:
I've become interested in handcoloring and the low print density
and ethereal qualities of IR prints seem particularly appropriate for
(my sloppy) hand-coloring. 

I just acquired a cheap 35mm rangefinder (Yashica GSN) which handled a
test roll perfectly. Planning on replacing the light seals and just
leaving IR film in it. Unfortunately, only auto exposure (and B/flash) and
the minimum ASA is 25, so that will limit my film and film choices
somewhat.  (Not TTL fortunately).

Eric Pederson
epederso@xxxxxxxxxxxxxxxxxxxx (no "n" in "epederso")
Professional home page:
	http://logos.uoregon.edu/uoling/faculty/pederson/pederson.html
Personal home page:
	http://darkwing.uoregon.edu/~epederso/

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