Rob Studdert wrote:
> On 5 Jan 2001, at 18:27, Shel Belinkoff wrote:
>
> > Lewis Kemper, in an article in the current issue
of Camera
> > Arts magazine, states that when bracketing for
critical use,
> > such as registering different layers with
different exposures
> > in photo editing software, one should bracket by
changing the
> > shutter speed because if you varied the aperture
the image
> > sizes would vary slightly.
Ok, I've been thinking about this for a while and I
think that I can see what he means. ( or I'm nuts.)
Say, for example, that you are taking a photo with a
main subject placed at 2 meters from the camera, and a
background subject at 4 meters. You bracket exposures,
and find that you prefer f/2 for your main subject (at
2 meters) and f/5.6 for your background subject (that
is at 4 meters). Now, assuming a normal to moderate
telephoto lens, the background subject will be out of
focus either way, but it will be *more* out of focus
at f/2. Now you would like to (in a photo editing
program) paste the f/5.6 background into the f/2
photo, but it will not be quite the same size as inthe
f/2 photo. It will be slightly smaller. Does this
make sense to anyone else? I don't do much with
photo editing software, but this is how it seems to
me.
Comments?
Thanks, William in Utah.
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