>> If I use a 300 mm IS lens on a D30 camera, the effective focal length
>> becomes 480 mm.  Does the IS still help two stops or does the change
in
>> focal length also change the effectiveness of the IS.  Since there is
a 60%
>> increase in focal length would there also be a 60% decrease in the
>> effectiveness of the IS?

One way to look at it: IS effectivity is decreased 60%, just as DOF is
decreased (also by 60%?).  But this is only because of the relative
cropping compared to a full-frame film image.

But another way to look at it: IS effectivity is the same, since any
cropped portion of the digital image compared to the same cropped portion
of a film image will appear the same.

Dave Herzstein
[EMAIL PROTECTED]
http://www.kjsl.com/~dave

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