typical (small) motion blurring

Pixie wrote:

"Chris Malcolm" wrote in message
...
Pixie wrote:

I've often wondered whether image stabilization can degrade a picture
slightly, even though it can let you take a picture in slightly lower
light
than would be the case with a camera that doesn't have image
stabilization?

It usually does. That's why leaving IS running when on a stable tripod
will usually degrade the sharpness, which is why most modern IS
systems have some kind of tripod detection system and politely turn
themselves off when they think they're on a tripod. If you're lucky
:-)

Thanks Chris for this reply. I guess image stabilization is a much debated
issue, as in this discussion:

http://www.cheapshooter.com/2007/08/...e-or-a-gimmick

Your tip to turn off IS when using a tripod is most interesting. I found a
Wikipedia discussion that agrees with you:

"Most manufacturers suggest that the IS feature of a lens be turned off when
the lens is mounted on a tripod, as it can cause erratic results and is
generally unnecessary. Many modern image stabilization lenses (notably
Canon's more recent IS lenses) are able to auto-detect that they are
tripod-mounted (as a result of extremely low vibration readings) and disable
IS automatically to prevent erratic behavior by the IS and ultimately
reduced image quality."

http://en.wikipedia.org/wiki/Image_stabilization

You would think that IS would not have erratic behavior because the camera
is securely mounted on a tripod, I wonder why this happens?

Economics. It would be possible to make an IS that behaved well to
such a high resolution that it never drifted a single pixel, but the
cost would be astronomical. In practice they make it work well enough
that you probably won't notice any IS blurring, i.e. it's no better
than the lens, autofocus, etc., of the rest of the camera. Which means
that there will at least be a little pixel jitter.

In some cameras you may also get position normalisation drift if the
camera was moved about quite a bit before taking the shot. If trying
to follow that movement pushed the IS off to one side, when left
stable it will gradually creep back to its central position, which on
a long exposure can leave an odd smear in the image.

Would IS also
behave erratically if someone is able to handhold a small camera very
steadily? I have often rested a camera on a ledge or similar to keep it
steady, so I guess I should turn IS off then also?

As so often with complicated technology the answer is that it
depends. You'll simply have to experiment if this is impprtant.

When I went to buy a camera, they told me to buy one without IS if I wanted
the best image quality. But if you can turn IS off when you want to, it
might be better to get a camera with IS. However, it looks like you need to
know quite a lot about IS before using it, not everyone would think to turn
off IS when the camera is on a tripod!

Modern cameras usually do a very good job when left to their own
devices. Generally speaking you only need to care about these esoteric
details when you're pushing to get the maximum possible performance
out of your kit.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Pixie wrote:

Another point, even when the camera is on a tripod, it may pay to use the
self timer function, I have found using this improves the clarity of
pictures slightly.

The timer may allow residual oscillations of the tripod/camera set up
to die down. These can sometimes be surprisingly large, e.g. if using
a lot of extension column. It also removes shutter press
movement. Even better is using a remote shutter release.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

"Chris Malcolm" wrote in message
...
Pixie wrote:

Another point, even when the camera is on a tripod, it may pay to use the
self timer function, I have found using this improves the clarity of
pictures slightly.

The timer may allow residual oscillations of the tripod/camera set up
to die down. These can sometimes be surprisingly large, e.g. if using
a lot of extension column. It also removes shutter press
movement. Even better is using a remote shutter release.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]


Some cameras will allow a delay between the mirror flipping up and shutter
curtain movement. Some cameras will allow you to flip the mirror up with one
press of the shutter and release the curtain with the second press. A remote
release does help. Nikon D-200 has both of these features. I am sure there
are others.

My 80-400mm does some funny things mounted on a tripod.

On 8 Mar 2008 11:34:56 GMT, Chris Malcolm
wrote:

Pixie wrote:

Another point, even when the camera is on a tripod, it may pay to use the
self timer function, I have found using this improves the clarity of
pictures slightly.

The timer may allow residual oscillations of the tripod/camera set up
to die down. These can sometimes be surprisingly large, e.g. if using
a lot of extension column. It also removes shutter press
movement. Even better is using a remote shutter release.

The 'restless earth' can be further amplified by
buildings, or other structures depending on their
construction. A remote shutter release would be a boon.

On Sat, 8 Mar 2008 18:07:34 +1300, "Pixie" wrote:


Perhaps the only way is to run a few tests with your own camera, both with
IS on and IS off when your camera is on a tripod and compare the results. In
my case, I found that having IS turned off produced slightly better results
than when IS was on (when the camera was on a tripod). So, I will turn IS
off in future when the camera is on a tripod.

If you are using a P&S camera with digital zoom and an EVF it is easy to test.
Just put the camera on a tripod, zoom in as much as possible, including full
range of digital-zoom. Point it at some distant contrasty scene with a lot of
detail. Wait for the IS to settle down. Then just watch in the viewfinder to see
if there is less than 1 pixel-width of motion in any sharply defined edge or
detail for about a minute. If you see zero motion then you don't need to turn it
off when on a tripod. If you are doing this on a wooden floor try to not shift
your weight because even that slight motion from floorboard to tripod might be
enough to wake-up the IS mechanism in your camera/lens. The same is true if
doing this near a road with heavy traffic. Trucks can impart a lot of motion
into the ground. People who are into holography and have to keep the distance
between subject and film to within 1/4th wavelength of light are well aware of
this and go to great lengths to isolate their holography bench from any nearby
freeways in the vicinity of their labs by using extensive air-cushioning
methods.

In all my cameras the IS settles down after 2 seconds of being on a tripod, but
I put the camera on a self-timer for 3 seconds to be sure. As well as to help
with residual tripod vibrations.

Speaking of which, you might have experienced blur from not allowing vibrations
to dampen out of the tripod.


Another point, even when the camera is on a tripod, it may pay to use the
self timer function, I have found using this improves the clarity of
pictures slightly.

Very important. Astronomers are well aware of this when using higher-power
eyepieces on their telescopes. Telescope mounts, as sturdy, bulky, and heavy as
they are (the base of mine alone weighs over 150 lbs, sturdy cast-iron, w/
telescope over 250 lbs.) are still subject to vibrations. They are usually given
the "tap-test" to see how long it takes for a magnified star to stop swinging
wildly in the display. Even with my telescope on highest power it can take
nearly 30 seconds for it to stop vibrating from a tap-test depending on the
telescope's mass orientation. Some poorer telescope mounts and simple tripods
can take over a minute for all vibrations to settle down. It is a common
practice in smaller telescopes with poorly made tripods (your typical
high-quality camera tripod) to put a planet or star just outside of the FOV of
the eyepiece, so that by the time the object moves to the center of the eyepiece
from the earth's rotation all vibrations in the tripod will die out by then,
hopefully. In a slight breeze this can be impossible. You can help this by
putting sorbothane pads under each tripod foot, as well as hanging a heavy
camera bag (or other weight) suspended below the center of the column of the
tripod.

You'd be surprised just how much that tripod might be vibrating and for how long
but you can't see it due to the low image-magnification factor in all nearly all
camera lenses with your viewfinder, but your pixels will sure notice it.

On Mar 7, 10:14*am, dale_78 wrote:
On Thu, 6 Mar 2008 09:09:21 +1300, "Pixie" wrote:

"Pooua" wrote in message
...
On Mar 4, 5:43 pm, James1234567 wrote:
Could anyone point me to any information on this question: If a
person is attempting and reasonably capable of holding a digital
camera steady, how many pixels of blurring, due to unintended motion,
would by typical for the image taken by the camera?

What if someone is under stress?

Thanks, J

That depends on the zoom and the pixels and probably a bunch of other
factors. It is fairly easy to hold a wide-angle lens steady in bright
light with a fast exposure. It is virtually impossible to hold a 300
mm lens under low light and long exposure steady by hand.

I would agree with this answer. There's also the size of the camera to take
into account. If it's a big heavy thing that doesn't have image
stabilization, it pays to check each picture straight after you've taken it
to see that the image hasn't blurred through camera shake (even in good
light).

I've often wondered whether image stabilization can degrade a picture
slightly, even though it can let you take a picture in slightly lower light
than would be the case with a camera that doesn't have image stabilization?
But even with image stabilization, it's probably not going to help much with
the example you give above about the 300mm lense in low light and with a
long exposure.

On the contrary. If your hand-held skills are admirable. I have obtained
1-second long tack-sharp exposures often with a 430mm lens.

Yeah? Let's see you do that for 5 or 10 seconds! Sometimes I can do
it, but it is quite difficult and I have to be feeling pretty good (or
braced against something solid) to manage it.

But you must turn
off IS from "continuous" mode and put it on "shoot only" mode. This way you can
stabilize your camera as much as possible on your own with the instant visual
feedback before the shot. You can't see how much you are shaking the camera with
IS turned on. Only during the actual exposure should you let the camera take
over.

That's interesting advice. I don't use IS very much, because the only
lens I own that has IS is going bad. Last year, I rented a Canon
28-300 mm lens with IS, though, and it threw me that it had 2 settings
for IS. I did OK with Mode 1, or whatever it was, I guess.