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Old Nov 22, 2004, 12:47 PM   #1
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Now i am sure you know i am not as much of an einstien when it comes to in depth knowledge on cameras as some of you out there:-). but i will tell you what i do know!! the correct combination of shutter speed and aperture in all situations to eliminate camera shake!! any photographer worth his/her salt should be able to do that?!! whichleads me to my initial question, IS is it for dummies?
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Old Nov 22, 2004, 1:16 PM   #2
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mweb wrote:
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Now i am sure you know i am not as much of an einstien when it comes to in depth knowledge on cameras as some of you out there:-). but i will tell you what i do know!! the correct combination of shutter speed and aperture in all situations to eliminate camera shake!! any photographer worth his/her salt should be able to do that?!!
As a general rule of thumb, you want to have a shutter speed of 1/focal length or faster to help reduce blur from camera shake.

So, if you're shooting at your camera's maximum aperture already, and shutter speeds still aren't fast enough, you can either use a tripod, or get a camera with IS (which gives you around 2 to 3 extra stops). So, without a tripod, you'd need a model capable of shutter speeds 4 to8 times as fast in the same lighting conditions to prevent blur from camera shake (and if you're already at your maximum aperture and ISO speeds, you'd have no choice to to use a tripod).

Let's take a real world example:

If you are shooting indoors without a flashwith the lighting levelat an EV (Exposure Value) of 6 (typical for"well lit" interiors) at an ISO speed of 100 and an aperture of f/2.8, the shutter speed needed for proper exposure would be approximately 1/8 second.

Now, the problem with a shutter speed this slow, is that most users will get motion blurfom camera shake unlessusing a tripod -- even shooting at full wide angle on most models.

As a general rule of thumb, just to reduce blur from camera shake, you need shutter speeds of 1/focal length or faster. Of course, this isis only a rule of thumb. Some users can hold a camera steadier than others, and some users will require faster shutter speeds compared to others.

So, let's say you're shooting at a 35mm equivalent focal length of 100mm. In this case, you'd want shutter speeds of 1/100 second or faster to prevent blur from camera shake (1/focal length).

Even with a relatively bright f/2.8 lens, with lighting at an EV of 6, increasing ISO speed to 400 (which will be noisy on most non-DSLR models), you'd only have shutter speeds of around 1/30 second for proper exposure (less than one third the recommended shutter speed to prevent blur from camera shake without a tripod at a 100mm equivalent focal length).

Yet, a model with a stabilized lens would still be able to get pretty sharp photos without a tripod in the same conditions (since you should gain at least 2 stops -- which means that even though you're shooting at 1/30 second, f/2.8, ISO 400, the Image Stabilization would reduce the shake,as if you're shooting at 1/125 second or faster.

In other conditions with more light, you may be able to keep ISO speeds set much lower (for less noise), compared to a model without Image Stabilization.

So, it can be a big benefit in some conditions, compared to a model without it (allowing hand held photos that would be virtually impossible in some conditions without a tripod, and allowing the use of lower ISO speeds in other conditons compared to models without a stabilized lens).


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Old Nov 22, 2004, 1:17 PM   #3
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Yes, you can eliminate the effects of camera shake by using a fast shutter speed and opening up the lens. However, that combination of shutter speed and aperture may not produce the kind of shot you want. Depth of field will be very shallow. If you are trying to do "fuzzy" water effects or night shots, you need slow shutter speeds. A tripod will help but if the tripod is not a good sturdy, heavy one, it might shake more than your hands.

Image stabilization will help in many of these cases. Image stabilization lenses are expensive but can help to save a good picture.

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Old Nov 22, 2004, 1:58 PM   #4
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Why? Because with image stabilization (or vibration reduction) I can get a shot at night that I would otherwise not be able to. I can shoot at 200mm f/2.8, use an ISO of 1250 and get away with a 1/25s exposure without flash, for an awesome available light shot and creamy smooth background. And did I mention I can do it handheld too? :-)
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Old Nov 22, 2004, 2:27 PM   #5
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MMMMMMMMMMM interesting, second question. does IS have any negative effect on the quality of output?
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Old Nov 22, 2004, 4:00 PM   #6
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I'm not sure what the negative affects are, but I know it is suggested on some IS lenses that you turn the IS OFF if you are using a tripod. I'm not sure what happens if you don't - I'm pretty good about turning mine off when I use the tripod but then I hand-hold 90% of the time.
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Old Nov 22, 2004, 4:08 PM   #7
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So JohnG you use IS lenses on a Canon SLR ?
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Old Nov 22, 2004, 7:43 PM   #8
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I have the Canon 28-135 USM IS lense. That is the only one I have with IS. I do notice the IS is useful as I can handhold to 1/15 and still get some pretty good results.
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Old Nov 22, 2004, 9:55 PM   #9
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I have 3 lenses with image stabilization.

The problem that JohnG talks about is that the earlier versions of IS work by detecting the vibration... but if the vibration is too small they still try to correct against it and fail. This actually causes the moving element (the element that is moved to counter the vibration) to introduce improper movement into the lens which distortes the picture (like camera motion blur.)

Because no matter how steady the tripod is, even a little wind or the action of the shutter can produce small vibrations which will confuse the IS system.

I also have two lenses that work fine with IS on on a tripod, and I love it. I am always shooting outdoors and I need IS to counter the wind induced movement on my big lens.

Eric
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Old Nov 23, 2004, 3:55 AM   #10
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While I take my hat off to the more detailed physics explained here, in a nutshell, I know I have missed some great wildlife shots because I simply didn't have time to diddle around with all the right settings, for a good low light shot. I am looking forward to my next digital camera (maybe Nikon's 8800) having an image stabilizing system. I'm sure this will help expand the number of possible shots I can take when I need to get the camera up and clickingin as little time as possible. Just one good reason I can name to want it. Best regards,

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