Re: Introduction and ? about Digital Infrared Photography

["Jason Revell (in5)" <jason.revell@xxxxxxxxx>]

>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.

The "strongest" IR filter I use is the B+W 094, this cuts out all
wavelengths below 1,000nm.  This would give no image, or
VERY faint indeed if use with IR film.  It is surprising the difference
this filter makes.  I do IR examination of art works and what shows
nothing on HSI with a 87c can show a lot when viewed with a video
camera and this filter.
If anyone knows of a higher cut-off filter please could you let me
know, as the camera's are sensitive to well over 1,000nm and the
more I can cut out the better.

>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.)

The bets way to get a good guestimate for exposure is by using
the film's sensitivity curve.  Draw a line trough the cut off point of the
filter and then measure the %age of area lost.  This will then tell
you how much you need to increase your exposure by.
i.e. only 6% of area left means increase exposure by 4 stops.

Hope this is of help and could save you some of your CHEAP
film.  :-)

Jason Revell
jason.revell@xxxxxxxxx
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