2 stop IS - What does it mean in practice?

[swag72]

OK, not the dumb question it first seems!! I know that IS reduces camera shake. What I was wondering was the 2 stop, 3 stop IS stuff. I was thinking about it literally .............. Here goes!!

Using my camera in manual, I take a reading and the shutter speed is say 1/500. If I have 2 stop IS, 2 stops on from there is 1/125 (Right?), so does that mean I could use 1/125 without additional shake? But then, wouldn't that mean my shot would be under exposed.

Don't know if I've phrased this well, but hope that my rambling makes sense.

 

[daftbugga]

yes 1/500 to 1/125 is indeed 2 stops

so your theory is correct ,as for causing over exposure .not if you then close the aperture down by 2 stops.

and your rambling does just about make sense . what about mine ?

 

[seriousrikk]

Ignore the exposure aspect and you are there.

Say you know you can hold your lens steady at 1/125th of a second, but because light levels are so low that shutter speed is not possible. With 2 stops of IS you could go down to 1/30th of a second and the lens woud still be steady.

 

[Gofer]

OK, not the dumb question it first seems!! I know that IS reduces camera shake. What I was wondering was the 2 stop, 3 stop IS stuff. I was thinking about it literally .............. Here goes!!

Using my camera in manual, I take a reading and the shutter speed is say 1/500. If I have 2 stop IS, 2 stops on from there is 1/125 (Right?), so does that mean I could use 1/125 without additional shake? But then, wouldn't that mean my shot would be under exposed.

Don't know if I've phrased this well, but hope that my rambling makes sense.

Yes for that particular shot but it would allow you to use an aperture two stops smaller which would bring the shutter speed down to 1/125.

 

[foggy4ever]

As you stop down your shutter(1/500,1/250,1/125) speed you would need to compensate by closing your aperture 2 stops depending on your meter reading. Or you could change ISO which ever suits your needs.



I need to type faster!

 

[swanseamale47]

What that doesn't take into account is any movement of your subject, if for example you needed a fast shutter speed to "freeze" movement, the IS won't help in that situation, it's just letting you hold the lens steadier at a slower speed in effect. Wayne

 

[Suvv]

OK, not the dumb question it first seems!! I know that IS reduces camera shake. What I was wondering was the 2 stop, 3 stop IS stuff. I was thinking about it literally .............. Here goes!!

Using my camera in manual, I take a reading and the shutter speed is say 1/500. If I have 2 stop IS, 2 stops on from there is 1/125 (Right?), so does that mean I could use 1/125 without additional shake? But then, wouldn't that mean my shot would be under exposed.

Don't know if I've phrased this well, but hope that my rambling makes sense.

Your shot would be overexposed. 1/125 is longer / slower than 1/500 so more light gets in.
As mentioned, change the aperture to compensate.
Close it down by 2 stops, not it open as stated by foggy4ever.
It allows you a greater range of shutter speeds and therefore a greater range of apertures.

 

[foggy4ever]

Your shot would be overexposed. 1/125 is longer / slower than 1/500 so more light gets in.
As mentioned, change the aperture to compensate.
Close it down by 2 stops, not it open as stated by foggy4ever.
It allows you a greater range of shutter speeds and therefore a greater range of apertures.

thanks for the correction sometimes my fingers don't type what my brain is thinking.

 

[Suvv]

thanks for the correction sometimes my fingers don't type what my brain is thinking.

I know the feeling. I had to read my reply 3 times before posting to make sure that it was correct

 

[foggy4ever]

I know the feeling. I had to read my reply 3 times before posting to make sure that it was correct

spent all of saturday at cadwell shooting bikes in manual for first time. It gave me a much better understanding of the exposure triangle, then get it wrong when trying to help:bonk: