Re: Flash and IR filters and Konica 750

["Thomas H. Hogan" <flzhgn@xxxxxxxxxxxxx>]

Dear Clive,

My guess is that the long exposure used with the Hoya 87 IR
filter on the lens allowed enough long wavelength (~750nm)
to give you nice infrared exposures but that the flash exposures
which were probably at the synch speed (1/60sec?) were not.

If you repeated the experiment using an incandescent light
source like a low wattage tungsten bulb behind the #87 filter
and long exposures (1/4 sec ?) then you might get sufficient
infrared light of the wavelength required to expose the film.
(If the tungsten light is too bright it might burn the #87 gel.)

You'd have to do this in a darkened room or have a #87 filter 
over the film/camera as well as the light source.

Hank
Clive Warren wrote:
> 
> Dear All,
> 
> Well the experiments with 120 Konica 750 IR have been very interesting.  I
> can report superb results with the following:
> 
> Hand Held Meter rating at 9 ASA
> Hoya 87 IR filter on lens
> f16   1/4 sec
> 
> Process Ilford HC for 6 minutes
> 
> High contrast, the prints will be black skies, white foliage etc etc.
> Can't wait to print the negs..... had planned to do it today but it'll be a
> couple of weeks now as my current condenser enlarger only goes up to 6 x 6.
> Am thinking about an LPL colour head enlarger as a replacement - anyone
> have experience of this kit?
> 
> Flash experiments a complete failure:
> 
> Rated at 50 ASA
> No filter
> Flash head covered with two sheets of exposed developed Ektachrome
> Used flash guide calculator and flash on auto
> 
> Process Ilford HC for 6 minutes
> 
> No discerible image on negs - nothing....  which is surprising.  Flash
> fired through the two sheets of film shows a green tinge, thought it would
> be red.
> 
> Does anyone have any ideas?
> 
> All the best,
> 
>               Clive   http://clive.bel-epa.com
> 
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