SLR Zoom

"Vinylmixer" writes:

I know that consumer cameras use 2x, 3x 4x etc to specify their
zooming capabilities, but SLR use lense length (or so im thinking)
but is there a site that shows photos of the zooming of these lenses
i.e. the difference a 200mm lense makes and a 400mm make compared to
say a 50mm etc etc

There are two *different* uses of "x" in talking about lenses
(including zooms).

In the binocular world, and the spotting scope world, people use "x"
to talk about magnification -- 8x binoculars make things eight times
bigger. We don't use that convention much in photography.

For camera lenses, talking about zoom lenses, "x" is used to describe
the zoom ratio -- the ratio between the longest and shortest focal
length the lens will go to. So a 100-500mm zoom is a 5x zoom -- and
so is a 12mm-60mm zoom. This is the usage of "x" that you see when
reading about consumer digicams.

For 35mm gear, a 50mm lens is by convention "normal". Since consumer
digicams usually specify the "35mm-equivalent" focal length rather
than the real focal length for their lenses, you can compute the
magnification by dividing the maximum stated focal length by 50 (this
gets you the "x" used for binoculars, magnification). So if a camera
claims a 28mm-280mm focal length (35mm-equivalent) zoom, the long end
is 280/50 or a bit better than 5 times magnification -- like 5x
binoculars.

At most camera stores, you can find a brochure or even counter mat
that shows a sequence of photos taken with all the different lenses in
some manufacturers lineup -- all from the same spot. That will give
you a pretty good visual idea what the different focal lengths mean.

However, since every consumer digicam I've checked has something
between 28mm and 40mm as the widest (smallest focal length)
35mm-equivalent focal length, the zoom ratio "x" factor actually gives
you a decent idea of the longest focal length provided -- a 10x lens
will be pretty reliably longer than an 8x lens on these cameras.
--
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RKBA: http://noguns-nomoney.com/ http://www.dd-b.net/carry/
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Jim Townsend wrote:

Vinylmixer wrote:

so does that mean u get more zoom?


Just a note on zoom..

Zoom is a verb.. It describes the apparent motion you see in
the viewfinder when you change the focal length of a variable
focal length lens. Not only can you zoom in, but you can zoom
out as well.

If you are close to an object where it is too big to get
in the frame, you can zoom OUT to make it fit.

FWIW, zoom came from the motion picture industry.. A camera
can move on several axis.. It can PAN (look left and right),
it can TILT.. (look up and down).. And finally it can
ZOOM.. (make objects appear to move farther away or closer).

or dolly in or out.


Fixed lenses have no zoom. There is no way to change the
focal length. If you want to zoom with a fixed lens, you
use your feet. You step backwards to make things appear
smaller and you step forwards to make them larger.

A fixed 1200mm lens on a 35mm camera will blow a set of 12X
binoculars away when it comes to magnification, but since you
can't change the focal length, the zoom factor of a fixed 1200mm
lens is 1X.

Jim Townsend wrote:

Vinylmixer wrote:

so does that mean u get more zoom?


Just a note on zoom..

Zoom is a verb.. It describes the apparent motion you see in
the viewfinder when you change the focal length of a variable
focal length lens. Not only can you zoom in, but you can zoom
out as well.

If you are close to an object where it is too big to get
in the frame, you can zoom OUT to make it fit.

FWIW, zoom came from the motion picture industry.. A camera
can move on several axis.. It can PAN (look left and right),
it can TILT.. (look up and down).. And finally it can
ZOOM.. (make objects appear to move farther away or closer).

or dolly in or out.


Fixed lenses have no zoom. There is no way to change the
focal length. If you want to zoom with a fixed lens, you
use your feet. You step backwards to make things appear
smaller and you step forwards to make them larger.

A fixed 1200mm lens on a 35mm camera will blow a set of 12X
binoculars away when it comes to magnification, but since you
can't change the focal length, the zoom factor of a fixed 1200mm
lens is 1X.

In article , Crownfield
wrote:

Jim Townsend wrote:


FWIW, zoom came from the motion picture industry.. A camera
can move on several axis.. It can PAN (look left and right),
it can TILT.. (look up and down).. And finally it can
ZOOM.. (make objects appear to move farther away or closer).

or dolly in or out.

and track left or right.

(I forget what the term is for vertical translation...crane? Something.)

In article , Crownfield
wrote:

Jim Townsend wrote:


FWIW, zoom came from the motion picture industry.. A camera
can move on several axis.. It can PAN (look left and right),
it can TILT.. (look up and down).. And finally it can
ZOOM.. (make objects appear to move farther away or closer).

or dolly in or out.

and track left or right.

(I forget what the term is for vertical translation...crane? Something.)