[LargeFormat] Re: flash exposure

[philip Lambert]

Thanks a lot. It does in part relate to large format  as I  photograph
building interiors and am wondering how to use the small flash gun in
question for multiple flashes on the same negative as my wide-angle lens
seems  sharpest at f16..... Maybe this is a different question. I remember
using big US flashbulbs with an immense output, one was usually quite
enough, PF100 I think they were, with exposure suggestions on the
carton....Philip
----- Original Message -----
From: "jpetrush" <jpetrush@webgenuity.com>
To: <largeformat@f32.net>
Sent: Saturday, December 30, 2000 9:22 PM
Subject: Re: [LargeFormat] Re: flash exposure


> Weeellllll, this is a tad OT for LF, but a legitimate photographic
question,
> so, to answer your second question first, every flash maker I have ever
> encountered over rates the output of their flash units by at least a half
> stop, sometimes more.  Either bias the film's ISO setting or dial in your
> "over exposure" factor.
>
> To find the output for a given unknown flash, try the following:
>
> Set your camera on a tripod at a fixed distance from the subject
> Load it with ISO 100 slide film.  This eliminates any processing
> "corrections"
> Set the lens at f/5.6 for a small unit, f/11 for a large powerful one.
> Begin a set of exposures with the *flash* 4 feet away from the subject,
then
> start backing up to 5.6 feet, 8, 11, and 16.
> Keep lens aperture and shutter speed (x sync) fixed throughout
> Take notes
> Evaluate the best of the batch
> Determine the guide number by multiplying the f number times the distance
of
> the best exposure.  This is your guide number in feet for ISO 100 film.
> To determine what f number to use at a given distance, divide 100 by the
> distance
> For films faster or slower than 100, add or subtract the number of stops
> from 100 to that f number.
>
> Or, get yourself a good flash meter <g>
>
> jp
>
> ----- Original Message -----
> From: "philip Lambert" <philip.lambert@virgin.net>
> To: <largeformat@f32.net>
> Sent: Saturday, December 30, 2000 10:03 AM
> Subject: [LargeFormat] Re: flash exposure
>
>
> > How does one achieve correct flash exposure?  I bought an old Canon
flash
> at a fair without a manual and ran off several exposures
> http://www.pairlist.net/mailman/listinfo/largeformat
>