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there's a rule of thumb in SLR photography which says that if you use a x
mm lens, then your shutter speed should not be less than 1/x s, to avoid
blurring due to camera shake when you don't use a tripod. e.g. if you use
300mm, then shutter speed should be more than 1/300s.
how can this be applied to digicams, since their lens actual focal length
are shorter than the SLR equivalent? is the figure taken the equivalent SLR
focal length or the digicam's focal length?

OlEnSh wrote:
> there's a rule of thumb in SLR photography which says that if you
> use a x mm lens, then your shutter speed should not be less than
> 1/x s, to avoid blurring due to camera shake
....
> how can this be applied to digicams, since their lens actual focal
> length are shorter than the SLR equivalent?

What is important is the angle of view of the lens and the duration of
the exposure. The rule of thumb is based on an assumption that a
handheld exposure involves movement of the camera at a rate which is
independent of other factors.

Thus, as the lens becomes longer, the angle of view becomes smaller, the
relative effect of a given amount of movement on the image becomes
larger, and so the duration of the movement needs to be reduced by using
a faster exposure.

Or more simply, double the lens length, halve the field of view, double
the effect of movement, so halve the duration of exposure.

It's just serendipity that for a 35mm camera the acceptable exposure is
about 1/f.l. (f.l. = focal length) and not 7/f.l. or 0.15/f.l.

For a camera with a different sensor system and hence different lens
lengths for the same image proportions, what matters is the field of
view. So if the total movement at 1/250sec is acceptable for a 250mm
lens on a 35 mm camera, it should also be acceptable for a 25mm lens on
a digital camera if the field of view is the same.

> is the figure taken the equivalent SLR focal length

Yes.

However....

Others may agree with me or they may tell me I'm dreaming, but I am
finding that I can go somewhat slower than this rule of thumb suggests
with my non-slr digital camera.

Presumably this is because there are no significant moving parts to
shake the camera. The shutter/aperture mechanism is rotationally
symmetrical, with no net "shake" of the camera, so the camera is far
smoother than a 35mm film camera with a mirror and two shutter blinds
hurtling about inside it.

Hi,

My problem is that becaue the camera is so light and I can use the LCD for
composing the picture, I tend to hold the camera away from my body, thus
introducing "hand shake".
I have to remind myslef to stedy the camera against my body, especially at
longer zooms in order to minimize shake.
Rosita

In article <bjmou7$1en$>,
says...
> there's a rule of thumb in SLR photography which says that if you use a x
> mm lens, then your shutter speed should not be less than 1/x s, to avoid
> blurring due to camera shake when you don't use a tripod. e.g. if you use
> 300mm, then shutter speed should be more than 1/300s.
> how can this be applied to digicams, since their lens actual focal length
> are shorter than the SLR equivalent? is the figure taken the equivalent SLR
> focal length or the digicam's focal length?

You must use the equivalent 35mm focal length to figure the minimum
shutter speed.

--
________________________________
Todd Walker
http://twalker.d2g.com
Canon 10D:
http://twalker.d2g.com/canon10d
My Digital Photography Weblog:
http://twalker.d2g.com/dpblog.htm
_________________________________

et (HRosita) writes:

> My problem is that becaue the camera is so light and I can use the LCD for
> composing the picture, I tend to hold the camera away from my body, thus
> introducing "hand shake".
> I have to remind myslef to stedy the camera against my body, especially at
> longer zooms in order to minimize shake.

If your camera has or *can* have a fairly conventional neck strap,
then push the camera *away* from you until the neckstrap is tight, and
pull your elbows in to your stomach. You've now got the camera held
in a *very* stable position (I find I can shoot this way at much
slower shutter speeds than I can pulling the camera up to my face) and
you can still see the LCD. One of the best things about consumer
digital cameras.
--
David Dyer-Bennet, <dd->, <www.dd-b.net/dd-b/>
RKBA: <noguns-nomoney.com> <www.dd-b.net/carry/>
Photos: <dd-b.lighthunters.net> Snapshots: <www.dd-b.net/dd-b/SnapshotAlbum/>
Dragaera mailing lists: <dragaera.info/>

> David Dyer-Bennet wrote:

>If your camera has or *can* have a fairly conventional neck strap,
>then push the camera *away* from you until the neckstrap is tight, and
>pull your elbows in to your stomach. You've now got the camera held
>in a *very* stable position (I find I can shoot this way at much
>slower shutter speeds than I can pulling the camera up to my face) and
>you can still see the LCD. One of the best things about consumer
>digital cameras.

Will try that as I always have the neckstrap on (with camera attached) -

Rosita