Re: Introduction and ? about Digital Infrared Photography

[Joshua_Putnam <josh@xxxxxxxxxxxx>]

>Date: Mon, 1 Feb 1999 19:21:38 -0500
>From: "Brad" <brad@xxxxxxxxxxxx>
>Subject: Introduction and ? about Digital Infrared Photography

>After getting some spam for the following site:

>http://www.kaya-optics.com/

>They are selling a filter for cam-corders and 
>digital cameras, anything that uses a CCD 
>(charged coupled device) for $120+.  This
>filter allows the camera to see through tight and
>thin clothing.  My thought was that it was an 
>infrared filter, and what a scam this was.  I hadn't
>looked into the prices of filters lately.

>But, my thoughts turned to simple hobby
>infrared digital photography.  I searched the web
>and only found one page, by Eric Cheng.  His 
>page offered some good examples, but little technical
>info.  I wrote to Eric, and he agreed that their wasn't
>much info out there, that I might have to open the 
>camera and remove an infrared blocking filter.  I
>wasn't too keen on that.

I use an opaque IR filter on my video camera for previewing
things before taking the time to shoot IR film, and I've found
that it works quite well.  It's a Sony Nightshot camera, the one
that all the "X-Ray" hype is about -- its internal IR-blocking
filter swings out of the way for use in monochrome IR mode.

The IR response of the Nightshot is definitely better than HIE.
It still gets quite a bright image through an 87A filter, with
such a deep cutoff that I have yet to figure out how long an
exposure to give HIE in bright sunshine to get a useable image.

Since scenes that may be interesting in IR are often rather dull
in the visual spectrum, in dry weather I mount the video camera
on my touring bicycle when I go for rides, and have had several
interesting images present themselves when I watch the tape later
on, allowing me to go back with film another day.

The X-ray hype isn't quite entirely bogus -- there's just enough
truth to it that people will probably keep grossly overpaying for
IR filters for a long time.  Thin synthetic clothing in close
contact with the body does become semi-transparent in the deeper
IR the cameras can pick up, but it's hardly anything to get
excited over.  Beer commercials on TV show more.

If you want to try the deeper IR filter, ignore the people
hyping "X-ray" filters for $100+ -- they're mostly just 87C
filters anyway.  I'm using 87A polyester foil filter material
from W.J. Markerink, who has shown admirable restraint by not
selling his entire supply for ten times what it's worth to
clueless bidders on Ebay :-)  If the sun ever comes out again
I'll get back to figuring out what exposure, if any, will allow
this filter to be used with HIE instead of the video camera.  I
got some faint images with multi-second exposures, but nothing
worthwhile.  (Thank goodness for expired bulk film in the walk-in
cooler at Glazer's -- perfectly good HIE at around $2/36 exp.)

-- 

 Josh@xxxxxxxxxxxx  is  Joshua Putnam / P.O. Box 13220 / Burton, WA 98013
                       "My other bike is a car."                   
                     http://www.wolfenet.com/~josh/
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