Re: Flash and IR filters and Konica 750

[Clive Warren <Clive.Warren@xxxxxxxxxxxxx>]

At 3:40 pm +0100 27/1/98, Gary Beasley wrote:

>>
>>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?
>>
>You might experiment with cheap black electrical tape lapped on a piece of
>mylar or something similar. This stuff acted like an 87 filter on the head
>of an infrared meter I was tinkering with a while back.
>As far as the flash, take it off auto if you can and calculate your f stop
>yourself. Do a wide bracket to find your true guide number for your
>filtration. The auto circuit may be totally skewed by the filtering,
>especially if it bounces any light back to the eye directly.


At the time it seemed reasonable to assume that the flash on auto would
tend to err on overexposure rather than underexposure, given that the
filter was blocking all visible light (except for a greenish tinge).

Will try it on manual after I have investigated spectral sensitivity curves
for the manufactured filter and Konica 750 film.


All the best,

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


*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************

------------------------------

End of Infrared-Digest V0 #371
******************************