1/x and 1.6x question

Hello - this is a great forum and I've learned a lot, but haven't been able to find an answer to this question.

I understand the guideline of 1/x shutter speed to prevent motion blur, where x represents the focal length. My question has to do with the 1.6x crop factor.

If you have a 100mm lens, would you need to set the shutter at 1/100 or 1/160? I know there are many other variables that come into play, but generally speaking, do you use the true focal length of the lens or the 1.6x equivalent?

Thanks in advance for your thoughts!

OK OK - slap me on the wrist. Found the answer in a sticky. Mods please delete.

My minimum would be 1/160 and I would try hard (meaning up ISO if necessary) to get 1/200. At 50mm or shorter I can go slower, down to 1/50 at 50mm lens, if necessary, just applies to myself, YMMV.

Trasmc - remember that the old guideline you refer to is just that - a guideline. Many people can hold cameras steadier than average, and many can't. Do some experimentation to determine what your limitations are with each focal length.

If you can afford IS lenses (Image Stabilization), you will be shocked at how low a shutter speed you can actually use and get acceptable results. I actually have a shot that I took with a 280mm lens on a 20D (Canon 70-200 f/2.8L IS + 1.4x extender, equivalent to a 448mm lens on a 35mm film body) handheld at 1/15th second and I find reasonably acceptable for camera movement blur. I wouldn't go that slow normally, but this "whoops" is extremely interesting.