Thanks for the tips. I will reply to some below:
[MAFUD:]
>"Lightless", the 1900 fires any number of remote servo flash units. If what
>you need is a trigger to fire other flash units, the 1900 will work,
>understanding the 1900 does *not* emit "light" from its on-camera position.
+++ Mafud, thanks, although I think the 1900 will be way too weak to shed
enough IR light on the scene, I imagine it has power more like led diodes
in IR TV remotes or flash AF assist beams. I would be glad to be mistaken
;) I will look into it.
[GLENN:]
d) You'll want BW IR, because if you use colour IR all you'll
see is red (which is how IR shows up -- IR shows a red,
+++ thanks for tip. E6 IR is WAY TOO expensive for such experiments, anyway
(here a single roll costs as much as 10 4x5" Velvia trannies in Quickload
b) You'll be using the flash at a fixed guide number, rather
than either auto or TTL modes -- you may have to determine
+++ I thought so, yet perhaps the mentioned Kodak's datasheet will help.
This is a project needing lots of experiments anyway (twill be my first IR!)
I need to get me some of that. (Any E6, or specific emulsions?)
+++ I always thought that any E6 will do. Propably best source for
inexpensive ones is ask at a local pro lab doing 4x5" and MF stuff, some
photogs throw the occassional "darn darkslide left in place!" frames in the
lab. I was able to get several rolls of 120 Ektachrome 64T for virtually a
smile ('twas after the "best before" date), and didn't do many shots on it
- so I will just left the rest of it blank. Somewhere on web is this
article (parts follow):
<quoted from "HandMade Photographic Images by George L Smyth">
I just determined what I had long suspected. I measured
the spectral transmission characteristics of one and two
thicknesses of
unexposed but developed E6 films and found them to be comparable to
that
of a Wratten 87 IR filter. In addition I also made some pix on HIE
film
through two sheets of D max EF sheet film and compared the pix to
some
taken through a "standard" IR filter, the Wratten 87.
The result of this is that it appears that one thickness
of E6 film is roughly the equivalent of an 87 filter but with a
broader
spectral response and with some 1% transmission valleys at 500 and
600
nm. Its transmission starts to drop from 1% at 700 nm to about 95%
at
800 nm. Two thicknesses of D max E6 are basically visually opaque
with
transmission dropping rapidly starting at 720 nm and dropping quite
rapidly
to 90% or so at 850 nm.
Maybe they might be closer to what a 88 is. Basically
the 2 sheets of E6 simply do not have as steep of a cutoff as the
Wratten
filters do nor as good a maximum transmittance. But they are
serviceable!!!
especially for placing over a flashgun where expensive Wratten
filters
tend to fry and buckle!
Picture-taking wise, the two thicknesses of E6 film did
not seem to degrade image sharpness significantly when used with
4x5 format.
I have not tested 35mm. They would obviously not matter much when
used
over a flash for inconspicuous flash photography at parties, etc.!
(camera
lens with or without additional filter over it).
</end of quote>
+++ I suspect that just any type of E6 will work, although he mentions only
Ektachrome. When you look tru a e.g. Fuji E6 black frames, you see only
purple/dark red colours.
[Bill Casselberry] (BTW, I am sorry but I forgot what your "bill" handle
was, to differentiate you from other bills on the list ;) It was sometimes
last year when we had this "discussion". Now W.Robb's Wheatfield Willie,
etc. What about you :o)
I haven't used these, but you want the flash head that outputs
IR light. From discussions on the IRList, the E6 film isn't all
that great for this & will be badly distorted after a few shots
from the heat - if you try it, have plenty on hand.
+++ Would you remember what were the other problems with E6 filter besides
cracking from heat?
+++ For my Sunpak, I can make an indeffinite amount of the E6 filters from
old Ektachrome for nearly a smile. But I would liked to use IR on a big
two-strobe Braun flash from 1950 (its power is similar to the Sunpak's, or
about 45-55 GN(m), but with almost 100 degree coverage at this GN!!!). It's
a powerful flash with separate power unit and BIG flashtubes generating A
LOT of heat - ideal for IR flash. Also, it charges off house AC, so it
doesn't do that buzzing sound. But it uses studio-flash-like reflector,
around 8" in diameter, so I would need bigger filters. 8x10" E6 is pretty
expensive. Better stick with one flash, though ;)
>> Will the TTL metering work well?
> your IR source will be constant, so manual exposure after a
> determination would be sufficient.
But the flash's auto sensor or body's TTL flash sensor wouldn't propably
work, or yes?
Manual flash wouldn't be much problem though, the Sunpak's got down to 1/64
manual output for precise aperture selection.
All my lenses (even zooms) got that red IR focus mark, so focusing
shouldn't be such a problem.
> that was me - I admit! "6400mm, guilty as charged" :^D
B-) Wow! Do you still have the scan from it on web somewhere? If yes,
where? I only got up to 2x500=1000mm ;-( What was the effective aperture
again?
Now, how should I beat you ;-) I will have quarter-dioptre (4000mm) glass
lens made, and another shorter negative one, to construct an 8000mm/256
TELEPHOTO ;-D
Frantisek
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