PCA Cala <PCACala@xxxxxxx> moved upon the face of the 'Net and spake thusly:
> Hello Tatu:
>
> << . . . [using] a 90mm macro, but its hard to use small apertures without
> loosing smooth backgrounds. >>
>
> What do you mean by smooth backgrounds? Out of focus? The 90 will throw them
> out of focus faster than a 50 mm macro. The 200 would have very shallow depth
> of field and throw them out of focus even faster.
>
In macrophotography, that's not so.
If you keep the *magnification* the same, depth of field is only
dependent upon aperture, and *not* focal-length.
Obviously the working distance will vary with focal length, and for a
given focal length DoF will vary with subject distance, *but* in
macrophotography changing lenses will not gain depth-of-field.
Chris.
--
Christopher Biggs -- chris@xxxxxxxxxxxxxx - Ph+61-7-3270-4266 - PGP & MIME OK
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