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Old Feb 11, 2008, 3:57 PM   #21
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Old Feb 11, 2008, 4:00 PM   #22
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shmueli2 wrote:
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dear ac.smith , thanks

I have learned quite a lot from your answer, however the stops issue is not clear to me. how do you decide how many stops you are below the correct one? please explain.

shmueli
Stops is a frame of reference for the effect of changing either aperture or shutter speed based on it's effect on exposure. Changing the aperture from f4 to f5.6 reduces the light striking the sensor by 1/2, changing from f4 to f2.8 doubles the amount of light hitting the sensor. Likewise changing the shutter speed from 1/30 sec. to 1/60 sec. halves the amount of light striking the sensor, changing from 1/30 to 1/15 sec doubles the amount of light striking the sensor.
The rule of thumb for minimum shutter speed to avoid the effects of camera shake (this assumes stationary subjects so it accounts for camera shake only) is 1 over the 35mm equivalent focal length. With your S5 at max telephoto (436mm equiv.) the minimum shutter speed would be 1/436 sec. or in round numbers 1/500 sec. Using IS then you should be be able to use a shutter speed of 1/125 sec., two stops (1/250,1/125) slower than the normal minimum.The rule of thumb has been developed empirically and represents the average user under typical conditions, your mileage may vary.

Another example. Shooting an auto show this weekend I had to use 1/8 sec. at f2.8 for correct exposure. Most of my shots were at wide angle so my equivalent focal length was 35mm. The rule of thumb then says I should use a shutter speed of 1/30 sec. but I was able to use 1/8 sec., 2 stops slower (1/15, 1/8 )because of IS.

The IS functioned only to keep my subject, the cars which were stationary, sharp. People, which were moving were still blurred because of their own movement.

Hope this helps.

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Old Feb 11, 2008, 9:41 PM   #23
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to ac.smith

I was about to reply, when your useful comment came in. I, like most people, know that every f stop is half or double the next one. What I was puzzled about, was the "correct stop" that you mentioned. Suddenly I recalled the rule of thumb, concerning the correct ratio between the focal length and the shutter speed, and now it is fully understood

thanks agin shmueli
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Old Feb 11, 2008, 9:53 PM   #24
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Just a little trigger and it all comes back:-). In a forum like this one doesn't always know the background of the posters so I tried to be complete. Still wish you'd post a couple of problem pics. The analysis would be a challenge.
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Old Feb 12, 2008, 7:13 PM   #25
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shmueli2 wrote:
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...the rule of thumb, concerning the correct ratio between the focal length and the shutter speed...
In my experience, it's also a very complex function of the degree of excitement, hence adrenalin level & muscle tension of the photographer, faced with an unrepeatable shot.

Calm, calm, calm!


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Old Feb 14, 2008, 10:27 AM   #26
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Could you give me an idea of the difference between "optical" image stabilization and "digital" image stabilization? I'm trying to decide between two inexpensive compact cameras-- Olympus Stylus 1200 and Canon SD850 --to get my wife (while I wait for a backordered G9).
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Old Feb 14, 2008, 10:46 AM   #27
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jerry bird wrote:
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Could you give me an idea of the difference between "optical" image stabilization and "digital" image stabilization? I'm trying to decide between two inexpensive compact cameras-- Olympus Stylus 1200 and Canon SD850 --to get my wife (while I wait for a backordered G9).
Here is a decent discussion on the subject: http://en.wikipedia.org/wiki/Image_stabilization
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Old Feb 14, 2008, 11:28 AM   #28
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jerry bird wrote:
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Could you give me an idea of the difference between "optical" image stabilization and "digital" image stabilization? I'm trying to decide between two inexpensive compact cameras-- Olympus Stylus 1200 and Canon SD850 --to get my wife (while I wait for a backordered G9).
All digital image stabilization does is increase the ISO, letting your camera use faster shutter speeds. This will lead to noisier photos.
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Old Feb 14, 2008, 1:19 PM   #29
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AndyfromVA wrote:
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All digital image stabilization does is increase the ISO, letting your camera use faster shutter speeds. This will lead to noisier photos.
That's all it amounts to on some cameras but others do actually have routines as described in the wiki article and some combine both.

Beyond that some appear to combine optical (sensor-shift) with some form of digital. This is a quote from the Olympus Stylus 1020 page:

"DUAL IMAGE STABILIZATION. The 2-in-1 anti-blur solution. Sensor-Shift Image Stabilization, which keeps your shot steady by compensating for camera shake, combines with Digital Image Stabilization to capture crisp, clear images in any situation. "

They don't further define digital is their spec. sheets.

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