Re: Flash and IR filters and Konica 750

[Clive Warren <Clive.Warren@xxxxxxxxxxxxx>]

At 8:20 am -0800 27/1/98, Thomas H. Hogan wrote:

>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

>> 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?

Dear Hank,

Thanks for your comments and suggestions.

The flash exposures were taken in a dark room with the flash as only source
of illumination.  Various sources on the web have suggested that a flash
gun with IR filter will behave in a similar way to that when using normal
unfiltered flash light with a standard film.

The shutter used was leaf so shot at 1/250 just in case there was any
additional light as no IR filter was used on the lens.

I particularly want to use flash for a number of reasons - had hoped to be
experimenting with bounce this evening, however need to sort this problem
first.


All the best,

              Clive   http://clive.bel-epa.com


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