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If I'm using a lens with image stabilization will my camera body detect this and automatically lower the required shutter speed?

For example, say I set an aperture of f4 with a non-IS lens, and I want to have a fast shutter speed of 1/800. The camera detects this will lead to an under-exposed photo and will flash a warning at me in the view finder.

Then I attach an IS lens, and the image stabilization is enough such that 1/800 is now fine. Will the camera body know about the IS feature and no longer flash a warning at me in the view finder?

Does it depend on the camera body?

I have a Canon Rebel XS, and I'm thinking of purchasing a 70-200 f4L lens (non-IS). I'm curious whether, if I went for the IS version instead, the camera body would know about the IS feature or if I have to manually compensate and/or ignore the camera's warnings.

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2 Answers 2

up vote 5 down vote accepted

Your camera should be aware of any IS settings in the lens, but I'm not sure you understand how IS works. Say you're in Av mode and you half press the shutter button: the camera takes your aperture and adjusts the shutter speed to get the desired exposure, let's say normally exposed and a shutter of 1/800. Regardless of any movement or IS, that's the settings required to have a normally exposed image (not over or under exposed, nothing to do with blurry). If you shoot without IS and move the lens you may get a blurry image, but if you shoot with IS and you can remain reasonably still then the lens will adjust for that and give sharp images. This has the result as if you increased the shutter speed, but without actually increasing the shutter speed.

So, IS affects shutter speed as it affects blurriness without actually affecting the shutter speed as it affects exposure. If you use a tripod, IS has no value whatsoever.

Also, props for using the XS, I thought I was the only one.

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Thanks tenmiles - you nailed it. I wasn't getting the real point - I thought it was still related to exposure, but now I see how it's not. Thanks also to Hakon who essentially pointed out the same thing. –  Ross Johnston Jul 15 '12 at 23:10

To correctly expose a photo, you need a balance between shutter speed, aperture and sensitivity (ISO). This is regardless of any IS in the lens or camera. This means that attaching an IS lens will not automatically give you a correct exposure. What you do get is the option of using a slower shutter speed (e.g. 1/200 instead of 1/800) without getting blurring caused by camera movement in the photo, which then might give you a correctly exposed photo.

Most cameras will give you a combination of shutter speed, aperture and ISO to correctly expose the photo if you don't use full manual mode. I don't know if any cameras will use a slower shutter speed instead of higher ISO or larger aperture while using a IS lens.

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