----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, September 24, 2001 3:44 PM
Subject: Re: constant aperture zooms
> In a message dated 9/24/01 2:17:36 PM !!!First Boot!!!,
[EMAIL PROTECTED]
> writes:
>
> << Constant aperture zooms are very nice for fill flash, even
with
> auto everything cameras, as the background will tend to stay
at
> the same density, no matter what focal length you are
shooting
> at. >>
>
> I'm sure this is self-explanatory to most of you, but not to
me. ....."the
> background will tend to stay at the same density".. Why?
When using fill flash, the flash controls the brightness of
forground subjects by varying the amount of light output. This
will keep forground subjects relatively the same. Varying the
aperture will change the density of objects outside of the flash
range.
This is very obvious (and quite a problem) when you shoot a
wedding using a variable aperture zoom lens. Using the wide
setting to get the entire wedding party at the alter, then zoom
in to get just the bride and groom, the background of the second
picture, while exactly the same in relationship to the subject,
will darken significantly, while the subject will stay
approximately the same due to the flash firing hotter.
William Robb
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