What exactly is "Image Stabilization"?

I'm a total newbie in digital camera. What exactly is Image
Stabilization and how does it apply in practical use? As I understand
it, camera shaking blur becomes a problem when you shoot under low
lighting levels and you don't want to turn on the flash. This is where
you would need I.S..

Would IS improve anything if you take shots in an outdoor setting with
plenty of lights? What about indoors when you use a flash?

Aside from the scenarios I've mentioned above, what else is I.S. used
for?

wrote:
I'm a total newbie in digital camera. What exactly is Image
Stabilization and how does it apply in practical use? As I understand
it, camera shaking blur becomes a problem when you shoot under low
lighting levels and you don't want to turn on the flash. This is where
you would need I.S..

Would IS improve anything if you take shots in an outdoor setting with
plenty of lights? What about indoors when you use a flash?

Aside from the scenarios I've mentioned above, what else is I.S. used
for?

It's really more a question of shutter speed and focal length. Obviously
low light situations call for a slower shutter speed.

As to how well one can hold a camera steady, that varies with the
individual. I seem to be able to do reasonably well, it's always best to
use any support available but having IS is a nice boost.
Dave Cohen

On 1 Sep 2006 09:04:43 -0700, wrote:
I'm a total newbie in digital camera. What exactly is Image
Stabilization and how does it apply in practical use? As I understand
it, camera shaking blur becomes a problem when you shoot under low
lighting levels and you don't want to turn on the flash. This is where
you would need I.S..

Pretty much, though IS can be useful even in moderate light levels. It
also depends on the focal length of the lens you are using; the longer
the focal length, the more useful IS tends to be (because small amounts
of physical shaking are more apparent with longer lens).

I should note that if you're shopping for a camera, you should be
careful to distinguish between real optical image stabilization (which
works by physically moving either a lens element or the sensor itself to
null out vibrations) and so-called digital image stabilization, which
just ups the gain on the sensor to allow shorter shutter times. The
former is the real deal; the latter doesn't do nearly as good a job.

Would IS improve anything if you take shots in an outdoor setting with
plenty of lights? What about indoors when you use a flash?

If there is really a lot of light (say full daylight), IS won't add
much. Ditto with most flash shots.

Aside from the scenarios I've mentioned above, what else is I.S. used
for?

You've pretty much covered it. It allows you to take less-blurry photos
in fairly low light. It's not a magic wand; if the light level falls
enough that the camera needs 1/2 second exposures or something, IS isn't
going to do the job. For that, you'll need to physically brace the
camera, preferably by using a tripod.

-dms

It's really more a question of shutter speed and focal length. Obviously
low light situations call for a slower shutter speed.

When you say "slower shutter speed", are you talking about setting the
ISO level or are you talking about increasing the seconds in "long
shutter"?

My current Canon camera, the one I'm about to replace, has ISO range
from 50 to 400. It can also do long shutter from 1seconds up to 15
seconds.

Here's an excerpt from one of the camera reviews I've read and could
not understand:
"(with Image stabilization) I was able to capture consistently
blur-free images at shutter speeds of about two stops slower than the
rule of thumb 1/focal-length, in this case at 1/30 second at a focal
length of 140mm."

Is he talking about the amount of time the shutter is turned on to
collect more light and not ISO setting? If that is so then what's 2
stops mean? 1 stop = 1 seconds?

I wont shoot without IS on my sony H5, you can shoot handheld at full
zoom almost 3500mm with a 1.7 tele extender and 57x. For most any shot
even bright daylight it makes a difference, just as a tripod gets you
the clearest shot. It realy helps.

On 1 Sep 2006 10:40:34 -0700, wrote:
It's really more a question of shutter speed and focal length. Obviously
low light situations call for a slower shutter speed.

When you say "slower shutter speed", are you talking about setting the
ISO level or are you talking about increasing the seconds in "long
shutter"?

My current Canon camera, the one I'm about to replace, has ISO range
from 50 to 400. It can also do long shutter from 1seconds up to 15
seconds.

Here's an excerpt from one of the camera reviews I've read and could
not understand:
"(with Image stabilization) I was able to capture consistently
blur-free images at shutter speeds of about two stops slower than the
rule of thumb 1/focal-length, in this case at 1/30 second at a focal
length of 140mm."

Is he talking about the amount of time the shutter is turned on to
collect more light and not ISO setting? If that is so then what's 2
stops mean? 1 stop = 1 seconds?

Yes, it's talking about keeping the shutter open for a longer time. In
this context, 1 stop means "double the exposure time". The standard
rule of thumb is that shutter speeds of 1/focal length are fast enough
to avoid shake. So, for a 140mm lens, you should use 1/140s or faster
shutter times. This particular IS system adds two stops, or a factor of
4, to the length of time which can be hand-held without seeing blurring.

1/140s * 4 = 1/35s

Many IS systems can give 3 stops (factor of 8) or even 4 stops (factor
of 16) improvement to the duration of blur-free exposures.

-dms

On 1 Sep 2006 10:40:34 -0700, wrote:

It's really more a question of shutter speed and focal length. Obviously
low light situations call for a slower shutter speed.

When you say "slower shutter speed", are you talking about setting the
ISO level or are you talking about increasing the seconds in "long
shutter"?

If you have your camera set to get a good exposure and suddenly
the amount of available light is reduced by 1/2, you have several
ways to handle it. You can change the shutter speed to keep it open
twice as long, or you can open the aperture to let twice as much
light through, or you can keep both aperture and shutter speed the
same, but increase the camera's ISO, which will amplify the signal,
but at the risk of reducing image quality.


Here's an excerpt from one of the camera reviews I've read and could
not understand:
"(with Image stabilization) I was able to capture consistently
blur-free images at shutter speeds of about two stops slower than the
rule of thumb 1/focal-length, in this case at 1/30 second at a focal
length of 140mm."

Is he talking about the amount of time the shutter is turned on to
collect more light and not ISO setting? If that is so then what's 2
stops mean? 1 stop = 1 seconds?

I think that you'd benefit greatly from a decent book on
photography. It doesn't have to be specific to digital cameras, so
if you see what appears to be a good book based on using film
cameras, that would do as well. As for "stops", take a look at an
old manual camera that has a separate control for aperture and
shutter speed. The aperture was usually controlled by rotating a
ring on the lens and the shutter speed by rotating a dial on the
camera body. They each had "detents", where you could feel a click
as you'd change settings by the smallest amount. This small amount
was referred to as a single "stop", and amounted to increasing or
decreasing the amount of light by a factor of 2. Familiar shutter
speeds were 1/30, 1/60, 1/125, 1/500 and 1/1000 second. Similarly,
consecutive apertures were if/1.4, if/2, if/2.8, if/4, if/5.6, if/8,
and so on. So if your camera was set to get the correct exposure
using f/2 and 1/1000 second, you could decrease the aperture by 3
stops (down to f/5.6) and lengthen the shutter by 3 stops (to 1/60
sec.) and the exposure would be the same. Reducing the aperture by
3 stops would reduce the amount of light by 1/8 (1/2 * 1/2 * 1/2),
but lengthening the shutter time by 3 stops would keep the shutter
open 8 times longer (2 * 2 * 2), resulting in the same exposure.

As for the image stabilization question, a common rule of thumb
used long before IS was invented was that the average person should
avoid taking pictures where the shutter speed was less than 1/fl.
(1/focal length). This was based on 35mm cameras, so if a 50mm lens
was used, 1/50 would be closest to the 1/60th second shutter speed/
Some people would be able to take reasonably blur-free pictures
using this camera and lens using a 1/30th second shutter speed, but
most people would start to notice blurriness in their shots with a
shutter speed this slow. In the example that you quoted, the rule
of thumb would indicate that a 140mm lens, if used hand-held, should
not use a shutter speed slower than 1/140th second. If Image
Stabilization was available, it could allow the shutter speed to be
decreased by at least 2 stops without increasing blur. This gives
1/140th sec. * 1/2 * 1/2 == 1/35th sec, or pretty close to the
1/30th second mentioned in the camera review. Recent lenses having
either Image Stabilization or Vibration Reduction can probably get a
3 stop benefit, which would allow the same 140mm lens to be used
hand-held down to 1/15th sec.

wrote:


Here's an excerpt from one of the camera reviews I've read and could
not understand:
"(with Image stabilization) I was able to capture consistently
blur-free images at shutter speeds of about two stops slower than the
rule of thumb 1/focal-length, in this case at 1/30 second at a focal
length of 140mm."

Is he talking about the amount of time the shutter is turned on to
collect more light and not ISO setting?
Yes, that's exactly what it means. But a higher ISO also
means that the camera is made more sensitive to light so
that a faster shutter speed can be used to get the same
image brightness as a slower shutter speed at lower ISO
(though high ISO also means more noise in the picture).

If that is so then what's 2 stops mean? 1 stop = 1 seconds?

No. Traditionally, shutter speed settings are provided so that
each setting is approximately half or twice as fast as the
next one - 1/30 sec, 1/60 sec, 1/125 sec, 1/250 sec, and
so on (many digital cameras also provide other speeds in
between these standard speeds). Each standard shutter speed
lets in twice or half as much light as the next one. Each
standard setting is called a "stop" because film cameras
usually had provision to set the shutter speed by way of a
mechanical device with a click stop at each setting.
Therefore, a change from 1/60 to 1/250 sec is a two-stop
change up, and a change from 1/500 to 1/30 sec is four
stops down.

An improvement of three stops with IS means that, if you
can shoot a blur-free picture at 1/250 sec, then IS will
let you shoot blur-free at 1/30 sec under the same conditions.

I should note that if you're shopping for a camera, you should be
careful to distinguish between real optical image stabilization (which
works by physically moving either a lens element or the sensor itself to
null out vibrations) and so-called digital image stabilization, which
just ups the gain on the sensor to allow shorter shutter times. The
former is the real deal; the latter doesn't do nearly as good a job.

If I am not mistaken some digital IS works by actually digitally
zooming the image rather than adjusting the gain. The processor then
actually only uses part of this zoomed image (the portion visible in
the viewfinder/LCD) but as the camera shakes or moves the processor
compensates by using keeping the theoretical area of interest from the
picture rather than the exact centre of the image. At least that is
how my digital camcorder seems to work.

Still your point is well taken - optical IS does a much better job
compared to digital (similar to how optical zoom is much better than
digital zoom).

On 1 Sep 2006 10:40:34 -0700, wrote:

It's really more a question of shutter speed and focal length. Obviously
low light situations call for a slower shutter speed.

When you say "slower shutter speed", are you talking about setting the
ISO level or are you talking about increasing the seconds in "long
shutter"?

My current Canon camera, the one I'm about to replace, has ISO range
from 50 to 400. It can also do long shutter from 1seconds up to 15
seconds.

Here's an excerpt from one of the camera reviews I've read and could
not understand:
"(with Image stabilization) I was able to capture consistently
blur-free images at shutter speeds of about two stops slower than the
rule of thumb 1/focal-length, in this case at 1/30 second at a focal
length of 140mm."

Is he talking about the amount of time the shutter is turned on to
collect more light and not ISO setting? If that is so then what's 2
stops mean? 1 stop = 1 seconds?

I really suggest you get a book on photo basics; there's a lot to
learn if you want to know how to control lighting.
Quickly: there are two ways ot control how much light gets to the
sensor, and they can operate interactively.
The shutter controls light by controling how long light hits the
sensor. it shoudl be obvious that a one second shutter speed will let
in 1/2 the ligt a 2 second speed does. It works the other way, too;
1/100 second lets in twice as much as 1/200 second shutter speed.
Doubling or halving he shutter speed alters the light by one stop, or
one EV (Exposure Value).
The aperture controls light by opening up or closing down, just like
the iris in your eye. The aperture is expressed in stops, or f:numbers
(also seen as f/numbers). The f:number is a ratio of the aperture
opening in mm to the focal length of the lens, also in mm. An f:2
lens' aperture is 1/2 the focal length of the lens (for example, 25mm
on a 50mm lens). Halving the aperture diameter is halving the amount
of light by one stop, or one EV.
F:numbers can be confusing, as they are usually given in a series that
corresponds to the square root of two; thus, f/1, f/1.4, f/2, f/2.8,
f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, etc. (This has to do with the
area of a circle, and math makes my head hurt, so I just take this on
faith. :-) )
The book will help.
Hope this helps.
--
Bill Funk
replace "g" with "a"