Reid <dontuse@fell-walker.co.uk> observed

Yes. But 'closer' only in the sense of magnifying the view.

Yes, but 'only that they get more in the frame.

Yes.

Not sure what you mean by 'proportions'. If you mean that the centre
(proprtionately) of a frame taken with a 24mm lens is identical
(picture-wise) of that taken with a 35mm, then yes.

Um. I think so, if you mean what I said above. '-)

HIH

Mike
[The reply-to address is valid for 30 days from this posting]

What happens is that the lense focusses on the sensor like it would
on film. But since the sensor is smaller, you "cut off" the edges
of the picture. So what happens is the equivalnet of a darkroom
magnification.

So you keep the proportions of the lense, just like on 35mm.

Not correct. A 50mm will produce a 50mm perspective on both lenses.
But the digital will have the edges cropped off.

DoF will be larger with the digital, since the smaller sensor
needs more magnification to become 5x7", and thus has a smaller
Circle of Confusion.

Life is always more complicated than it at first appears ;-)

OK, lets clear up a very common mistake. The relationship between the
size of your subject and objects in the foreground and background is
referred to as perspective. Contrary to popular opinion focal length
(ie whether you use a telephoto or wide angle) has absolutely no
effect on perspective. What does have an effect on perspective is the
distance between you and your subject (and foreground and background
objects). As you get further away from your subject, the apparent
distance between object gets less, hence you get a "compressed'
perspective. Because you are generally further away from your subject
when you use a telephoto lens, this 'compressed perspective' effect is
often attributed to the use of a telephoto lens, when it is in fact
due to the increased distance between you and your subject.

If you don't believe me, try the following exercise: Take two pictures
of the same subject without moving at all. Take the 1st picture with a
standard lens (eg 50mm on full frame 35mm film) and the 2nd with a
telephoto lens (eg 300mm). Then make two prints of the same size (for
the sake of argument lets say 6"x4" though it doesn't really matter).
Enlarge just the centre portion of the 50mm photo so the subject
appears to be the same size in both prints. You will end up with two
photos that are absolutely identical from a perspective point of view.

This is basically right, but what is usually called a 'focal length
multiplier' should really be called a 'field of view crop'. A 24mm
lens on my Canon 300D will have a similar field of view to a 38mm lens
on a full frame 35mm camera, but in other ways it will behave like a
24mm lens because the focal length itself hasn't been changed.

I assume by proportions you in fact mean perspective (you still
talking about the relative size of the the subject to foreground and
background objects right?). Working on this assumption remember what I
said about focal length has nothing to do with perspective.
Perspective is controlled by the distance between you and the subject.

To recap, a 24mm lens on a digital SLR will not produce an identical
image to a 38mm lens on a full frame camera, but it will have similar
field of view to a 38mm lens and conceptually it is convenient to
think of it as having become a 38mm lens (though it is still a 24mm
lens).

But despite the apparent complications it's really very simple and I
wouldn't get caught up in these things too much. Just bung the lens on
your camera and see what things looks like though the viewfinder ;-)

Cheers, Chris
------------------------------
Chris Osborne - Edinburgh
chris(at)cjo.info
http://aspects.cjo.info/

Completely wrong.

Long focal length lenses have a smaller angle of view.  Wide angle
lenses have a wider angle of view.  That's all.

Long lenses don't "get closer", they simply magnify the central
portion of the image that a wide angle lens would produce.  Neither do
they "make distant objects appear big relative to foreground objects".

The only thing that affects perspective (which is what affects the
relative size of near and far objects) is the location from which you
make the shot.  The perspective from a given location is identical,
regardless of the focal length of lens in use.

The subject of perspective is comprehensively covered in most books on
the basics of photography, in one of which you really should invest.

I seem to remember this was covered fairly comprehensively in one
particularly memorable episode of the TV comedy series "Father Ted".  

;-)