It's all about presentation. Let's use the SI's max landscape
presentation as an example: 1200x800.
When I take a photo for the SI I may crop out part of the frame to
remove distracting stuff or to improve the composition - but the amount
cut away is usually quite low. At worst it might be 25% in one or both
dimensions removed (up to 50% of the surface).
Then re-size for presentation at 1200x800.
So, 50% (or more) of the originally viewfinder framed image remains.
eg: "As I saw it" through the viewfinder.
BUT:
My camera is 6000 x 4000 pixels. If I directly crop a section out
without re-sizing to 1200 x 800 it is the same as a 5x zoom for the
presentation format.
In that case I've removed 96% of the original pixels and "zoomed in"
considerably for a given presentation size.
A mere 4% of the original in-frame image remains "as I saw it" through
the VF.
> As far as I'm concerned, if you have an 18/55 or 18/270 lens (as I
> do), you shoot as close as that lens can focus, and you crop down to a
> portion of that image...you're legal.
I'd propose that the litmus test here is "how well will it print" before
the cropped section was resized for the SI. My example above (4%) would
not print very nicely at 8x5.3 inches.
The guideline should perhaps be something like: before resizing for the
SI, would the cropped section print to 12x8 inches and look good?
(In photoshop one can "View printed size" assuming the screen pitch is
entered and the print pitch is set).
> Nikon has a "macro" setting,
> but it isn't macro and I never use it. Real macro is produced by the
> lens used (or the lens and an extension tube) and not by a mode
> setting.
If the "macro" is an in-camera thing, then it's not macro; if it's a
zoom lens with a "macro" mode then it's not macro but very-closeup.