# What is the "X" on Digital Camera Zoom

Tags:
Last response: in Digital Camera
Share
Anonymous
January 27, 2005 2:10:30 AM

I tried google with this question.
I have been wondering what those zoom specifications are. Like 3x, 4x
etc.
Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
It seemed to match the numbers for an s500 canon camera.
7.4 (W) - 22.2 (T) mm
(35 mm film equivalent: 36 (W) - 108 (T) mm)
22.2/7.4 = 3
Or is this a measure of how much the zoom is able to pull the subject
closer compared to the eye ( I remember reading that 50mm
on an SLR camera is equal magnification to what naked eye sees.

If it is just T (mm)/W (mm), why is it even important. As a small lens
without much magnification will have higher X, if it has an even
smaller W(mm)

Thanks
--nw

More about : digital camera zoom

Anonymous
January 27, 2005 2:46:20 AM

norris_watkins@hotmail.com wrote:
> I tried google with this question.
> I have been wondering what those zoom specifications are. Like 3x, 4x
> etc.
> Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
> It seemed to match the numbers for an s500 canon camera.
> 7.4 (W) - 22.2 (T) mm
> (35 mm film equivalent: 36 (W) - 108 (T) mm)
> 22.2/7.4 = 3
> Or is this a measure of how much the zoom is able to pull the subject
> closer compared to the eye ( I remember reading that 50mm
> on an SLR camera is equal magnification to what naked eye sees.
>
> If it is just T (mm)/W (mm), why is it even important. As a small lens
> without much magnification will have higher X, if it has an even
> smaller W(mm)
>
> Thanks
> --nw
>
Yep! It is the ratio of the longest focal length to the shortest F.L.
Bob Williams
Anonymous
January 27, 2005 10:43:11 AM

<norris_watkins@hotmail.com> wrote in message
> I tried google with this question.
> I have been wondering what those zoom specifications are. Like 3x, 4x
> etc.
> Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
> It seemed to match the numbers for an s500 canon camera.
> 7.4 (W) - 22.2 (T) mm
> (35 mm film equivalent: 36 (W) - 108 (T) mm)
> 22.2/7.4 = 3
> Or is this a measure of how much the zoom is able to pull the subject
> closer compared to the eye ( I remember reading that 50mm
> on an SLR camera is equal magnification to what naked eye sees.
>
> If it is just T (mm)/W (mm), why is it even important. As a small lens
> without much magnification will have higher X, if it has an even
> smaller W(mm)
>
> Thanks
> --nw
>

It is the ratio as you have calculated.
Related resources
January 27, 2005 12:46:55 PM

<norris_watkins@hotmail.com> wrote in message
> I tried google with this question.
> I have been wondering what those zoom specifications are. Like 3x, 4x
> etc.
> Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
> It seemed to match the numbers for an s500 canon camera.
> 7.4 (W) - 22.2 (T) mm
> (35 mm film equivalent: 36 (W) - 108 (T) mm)
> 22.2/7.4 = 3
> Or is this a measure of how much the zoom is able to pull the subject
> closer compared to the eye ( I remember reading that 50mm
> on an SLR camera is equal magnification to what naked eye sees.
>
> If it is just T (mm)/W (mm), why is it even important. As a small lens
> without much magnification will have higher X, if it has an even
> smaller W(mm)
>
It's the zoom ratio, the X is a stupid method. because a 28~280mm zoom and a
35-350mm both have a 10:1 zoom ratio and would both be marketed as 10X
zooms. Based on a normal 50mm lens a 10X magnification factor would be a
3090mm lens. NOTE: I used the 35mm equiv. as I was too lazy to do the math
(not enough coffee yet!)
Anonymous
January 27, 2005 1:02:37 PM

norris_watkins@hotmail.com wrote:

> I tried google with this question.
> I have been wondering what those zoom specifications are. Like 3x, 4x
> etc.
> Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
> It seemed to match the numbers for an s500 canon camera.
> 7.4 (W) - 22.2 (T) mm
> (35 mm film equivalent: 36 (W) - 108 (T) mm)
> 22.2/7.4 = 3
> Or is this a measure of how much the zoom is able to pull the subject
> closer compared to the eye ( I remember reading that 50mm
> on an SLR camera is equal magnification to what naked eye sees.
>
> If it is just T (mm)/W (mm), why is it even important. As a small lens
> without much magnification will have higher X, if it has an even
> smaller W(mm)

First off, you have to understand that the word 'zoom' when applied
to lenses does NOT refer to magnification.. It refers to motion.

Zoom is a verb used to describe the apparent motion that you see
in the viewfinder as you vary the focal length of a variable lens.

If you increase the focal length as you look through the
viewfinder, your subject will appear to 'zoom' towards you. In the
film industry, doing this is called 'zooming in'

If you decrease the focal length as you look through the lens,
your subject appears to 'zoom' away from you. This is called
'zooming out'.

Zoom allows you to adjust how close *or* how _far_ the subject
appears to be from the camera.

As others have said... Zoom is calculated by dividing the maximum
focal length by the minimum focal length. The greater the difference,
the more ability it has to make an object appear both further away
and closer. A 15-30mm lens has 2X zoom A 100-200mm lens has 2x zoom.

A fixed lens has *no* zoom. If you take a fixed 1200mm lens on a 35mm
camera for example, it can magnify enough to see the hairs on a fly's leg
at 100 yards. It can show an abundance of detail on the moon's surface..
But.. The maximum and minimum focal length is exactly the same..

So using the zoom formula: 1200mm / 1200mm = 1X.

All fixed lenses have a zoom of 1X no matter how powerful they are.
Anonymous
January 27, 2005 7:30:48 PM

<norris_watkins@hotmail.com> wrote in message
>I tried google with this question.
> I have been wondering what those zoom specifications are. Like 3x, 4x
> etc.
> Is this the ratio of the closest ( T ) zoom / farthest ( W ) zoom.
> It seemed to match the numbers for an s500 canon camera.
> 7.4 (W) - 22.2 (T) mm
> (35 mm film equivalent: 36 (W) - 108 (T) mm)
> 22.2/7.4 = 3

Correct. The "3x" (pronounced "three times") means the longest focal length
of the zoom is three times the shortest.

> Or is this a measure of how much the zoom is able to pull the subject
> closer compared to the eye ( I remember reading that 50mm
> on an SLR camera is equal magnification to what naked eye sees.

There really is no such thing as "equal magnification to what naked eye
sees." The magnification of the camera lens and the human eye cannot be
directly compared. The 50mm lens has been considered "normal" for 35mm
cameras since about 1925, but there really is no scientific basis for this.
Other focal lengths from 35mm to 58mm have been used as "normal" on 35mm
cameras, and no one can say that one is actually any more "normal" than
another.

>
> If it is just T (mm)/W (mm), why is it even important. As a small lens
> without much magnification will have higher X, if it has an even
> smaller W(mm)

It's just a measure of the zoom RANGE. You are correct that the "x" is not a
measure of lens magnification, e.g. a 35-105mm lens and a 70-210mm lens are
both 3x zooms, though the latter is twice the focal length (and will have
twice the image size) at either end of its zoom range.

The zoom range is important because it tells you how much flexibility you
will have in adjusting image size (magnification). Most zoom lenses built
into digital cameras are somewhere around 35mm (35mm film equivalent) at the
short ("W") end, though there are exceptions to this. So generally speaking,
4x or 5x zoom lenses will be longer (larger image size) at the "T" end than
will a 3x zoom lens. On the other hand, the 7x zoom lens on a Minolta DiMAGE
7 series camera is both substantially wider at the short end and longer at
the long end (28-200mm in 35mm equivalence) than a 3x zoom lens, which is
extremely useful. All else being equal, the wider the zoom range the better.

N.
!