Let's say, to make up some easy numbers, the camera shoots a 3Mp
picture. Whatever it sees, it spreads across all 3 million pixels -
whether that's the full cubicle or the face of the person working there.
What makes the picture look closer, whether by optical or digital zoom,
is that the face takes up more space in the frame.
Taking more space in the frame means that the face now uses the
same 3 million pixels that in a wider shot recorded the entire cubicle.
That's part of why digital lenses talk about magnification rather
than focal length, and why a 300mm digital zoom lens on my Nikon digital
is "equivalent" to a 450mm lens on my old FM.
But if I shoot wide and crop in PS, I actually remove a bunch of
pixels from the pic. To get the size back, I have to add pixels, and
that means PS has to interpolate colors and detail as it makes the
transition to give me back a portion of the original pic in the original
3Mp size.
That said, it can be done, and the result isn't really terrible,
especially for newsprint and online reproduction. But it's better if the
camera uses all the pixels it has in the shot, rather than doing the
conversion in PS.
On 2/6/2010 10:43 AM, Don Ferguson wrote:
> Yep, but my point is that with digital (rather than optical) zoom, the same
> thing happens whether it's on the camera or in PS.
