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RE: [APML] Cheap Dessicant to store film with
Jason:
The problem with your 'one point tonight, one point next Friday, ...' ideas
is that, as good a technique as that is for many types of experiments, it
doesn't work well for astrophotography. Air turbulence, jet streams,
humidity (not only at your level, but throughout the total air-column you
observe through, dust, dirt, smoke, volcanic ash, ... are all too variable
for testing over extended time periods. Most of these variables you have no
way to measure, so you can't correct for them. Trying to do a statistical
regression would take a huge number of samples at tremendous cost, and
probably give you statistical deviations where the film hypering would be a
minor component of the variability.
I've been doing 'process performance' analysis for years, and the unintended
influences from left field can drive you crazy. The 'butterfly flapping his
wings over the Amazon causing next years hurricane' demonstrates the idea.
-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Lane, Jason R
Sent: Wednesday, 04 August, 2004 14:14
To: Discussion of Film Astrophotography
Subject: RE: [APML] Cheap Dessicant to store film with
Hi guys,
... trimmed ...
As for being able to draw valid conclusions from the tests, this is simple.
The easiest way is to use a control. Jerry, your comment about film being
shot on different nights...maybe I wasn't too clear in what I meant. One
test sample shot on same night as a control sample would give one data
point. A test sample and control shot a fiew weeks later gives a second
data point. Several of these over a period of several months and you have
an idea of the effect over time. Of course, as with any experiment, you
should always describe the assumptions made and variables that could affect
the results. I thought this was common knowledge?
Thanks to all for the great insight and comments. That is what I was
looking for. I shall limit my ambitions to just keeping the moisture that
develops in my fridge and freezer off the film---which is the main thrust of
this exercise---rather than speculating about how well this would
"semi-hyper" the film. :)
Cheers!
Jason
-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Jerry Lodriguss
Sent: Wednesday, August 04, 2004 11:14 AM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Cheap Dessicant to store film with
Hi Kent,
I tend to mostly agree with you. If the purpose is to get the best
astrophotos, then with the films that are good for astrophotography today,
such as E200, you pretty much don't need to hyper them at all. So trying to
hyper by Jason's method would seem pretty much to be a waste of time.
On the other hand, if he is more interested in experimenting with different
hypering methods for the sake of experimenting, I would say, go ahead and
knock himself out. If he want's to experiment with real hypering to see if
there are any new undiscovered films that would be good for long-exposure
deep-sky astrophotography, I can sell him a complete hypering system real
cheap.
The problem is, that from a scientific standpoint, it's going to be almost
impossible for him to isolate the variables and draw any kind of valid
conclusions from his experiments because the film will be shot on different
nights.
I don't know why Jason wants to use calcium chloride, when he can get
silica gel just as cheaply: http://www.safetycentral.com/moisabdespac.html.
I think Chuck Vaughn puts a couple of grains of silica gel in the film can
and tapes it closed with electrical tape when he stores hypered techpan.
Jason also seemed to imply that he might be storing exposed film with his
experimental method. If so, I would advise against that. Not only would it
add another variable, but the latent image on extremely low light level
exposures does not store well. Long exposure deep-sky images should be
processed as soon as possible after exposure. I know some people like to
keep exposed film in the camera over the course of a couple of nights, and
I have certainly done that while camped out on an astrophotography
expedition for a week on a mountain, or in the desert, but keeping exposed
film for months is just crazy to try to save a couple of bucks (literally,
just a couple of dollars), considering the work and effort that went into
the exposures.
Now, storing unexposed film in a dry artificial environment with silica gel
makes a lot of sense if you are in a climate that is wet or high humidity,
like where I came from in the swamps of Louisiana, or like where I am now
in the bogs of New Jersey. But in a humid environment, I would certainly
not take the film out of its original canisters just to put it in a ziploc
bag with silica gel. I would put the unopened film cans in the ziploc bag
with the silica get, and only open it just before loading it into the
camera to shoot it. I wrap a big ziploc bag with silica gel around the
camera during the exposure (or better, flow nitrogen or dry air into the
camera during the exposure), and then store the exposed film in the
original ziploc bag with the silica gel in it for transport back home and
to the processing lab.
Jerry
>Someone once said that "those that don't learn from history are condemned
>to repeat it".
>Or another way of putting it, don't reinvent the wheel.
>
>Sure, Damp-Rid or any other dessicant can be useful, but only for storage
>and transportation of hypered film. The dessication part of the hypering
>process is to remove water and oxygen from the film being hypered. This
>requires a vacuum, the stronger the better and this can't be accomplished
>with just a dessicant like Damp-Dri.
>
>You seem to be trying to find a way to 'hyper' film without hypering it.
>That's an interesting goal, but so is alchemy.
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