Re: B&W IR w/Flash

[Jim Houha <houha@xxxxxxxxxxxxxxxxxxxxxxx>]

>Hi I'm new to the list (see bio below) and have a question about shooting IR
>with a flash. I have covered the flash with an 87c filter in hopes of taking
>discreet night-time photos. However, my first attempts at using this
>technique has produced negs that are consitently 3-4 stops underexposed when
>the subject is within 10 feet.. If the subject is any further away, negative
>density drops off to almost nothing
>
>Anyone out there have any advice? Here are the particulars:
>
>Camera: Nikon FE2
>Camera settings: f/16; Exposure Index - 200ASA; Shutter - A
>Flash: Sunpak 433AF (Dedicated)
>Flash settings: Manual; full power; 1000 ASA;
>Filter: on lens - none; on flash - Kodak Wratten 87C
>Film - Kodak Highspeed IR
>
>Thanks,
>paul
>

Hi Paul

If at f16 you were 3 stops overexposed for subjects at 10 feet, then f5.6
would be indicated. That gives your Sunpak 433 an Guide Number of 56 (in
feet) when used with HIE and a #87 filter. A guide number is nothing more
than the aperature times the distance.

So leave the flash on full power, set the shutter speed to the FE's sync
speed of 1/125, and divide 56 by the distance to the subject (in feet) to
get the f-stop. For example:

   subject at 28 feet,  use f2

   subject at 14 feet,  use f4

   subject at  7 feet,  use f8

   subject at 3.5 feet, use f16



Cheers,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jim Houha                                       houha@xxxxxxxxxxx
 


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