(meteorobs) Re: Off-Topic X-ray film etc.

[Richardson, Terry R.]

Ed,

Your lens is fast but they had even faster ones believe it or not. The phosphor screens had low efficiency convewrting x-ray ro light and of course if there was a patient involved, then the x-ray dosage would have been too high is the photographing lens had a slow f/ration. These lenses were produced in the 1950's when the only phosphor was calcium tungstate. there are better ones now.

Pretty much any film does a good job in the blue and UV. In film's early days it was the yellow and red sensitivity that was missing until the development of panchromatic films and then later infrared sensitivity was also developed again with the use of various agens. The situation is really a cousin of the photoelectric effect where shorter wavelength and thus higher energy photons (sudh as UV and blue) have the energy to transform the silver halide crystal so that is is reduced by development while red light and longer wavelengths lacks the energy.

I don't seem to have any ready information in my database on the spectral resonse of x-ray film to UV but I suspect is it uniformly good.

Below is a link with more information that might be useful to you. Also let me say I have followed your work from the post here and I admire what you do and have often tried to think of ways I might someday have some of my students try to collaborate with you perhaps analyzing data or doing spectra themselves. Also you should not rule out trying to get a grant for your work. Money is tight now and I am not an expert but there are probably ways to make that happen.  At least you should take a stab at it.

x-ray link->     http://www.e-radiography.net/radtech/f/film.htm

Clear skies,

TRR


-----Original Message-----
From: meteorobs-bounces at meteorobs.org on behalf of Ed Majden
Sent: Sat 9/3/2005 7:57 PM
To: Global Meteor Observing Forum
Cc: RASCALS
Subject: (meteorobs) Re:  Off-Topic  X-ray film etc.
 
on 9/3/05 15:17, Richardson, Terry R. at RichardsonT at cofc.edu wrote:

> Ed,
> 
> I am afraid I have some unfortunate news about your lens. The lens you have is
> called an "x-ray" lens because it was used to photograph the phosphor screen
> in an x-ray imaging sequence.

Terry:
    Thanks for the info on the Rayxar lens.  I didn't consider it being used
to photograph a green phosphor screen but your probably right.  I wonder why
the high speed in this case?  Do you know what the spectral characteristics
of X-ray film are?  What range do they cover.  Millman/Halliday used Kodak
spectroscopic 103-0 emulsion on glass plates.  Probably rather expensive if
still available.  Many of these emulsions are either not available or are
special order these days.  Back in the 1950's Peter Millman had a special
lens made for near UV spectra, quartz I think.  At least the 300 g/mm
transmission grating was ruled on a quartz blank.  I have a B&L precision
replica, blazed for 4000A that I use on normal lenses.  I bought it second
hand otherwise I would have got one blazed for 5000A. I can get down to
around 3600A/3700A with it.  Ian Halliday said he didn't know the exact
specs on their lens but used it for meteor spectroscopy.  It covered a range
down to 3000A but that was probably the limit set by atmospheric absorption.
Ian Halliday wrote a paper on his UV spectra, Publications of the Dominion
Observatory Ottawa Volume XXV - Number 12, A Study of Ultraviolet Meteor
Spectra. (1969).  A very interesting paper on this topic.  Unfortunately, as
an amateur I don't have the big dollars to spend, so I try and find surplus
stuff and hope for the best! ;-)

Ed

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