lens Focal = shutterspeed

[elfyrulz]

is it true that I need to match my shutterspeed with my SLR focal length to prevent camera movement?
let say a 80mm lens should have atleast 1/90+ shutterspeed and If I lowerd the shutterspeed to 1/60 that means I need to use a Tripod.

[Belmondo]

That's a good general rule, but not absolutely true for all situations.It is possible to shoot handheld at slower speeds with good results, but it takes practice.

[Jon]

As a rule of thumb it applies directly to 35 mm. When you're using a DSLR with the multiplication factor, you need to use the apparent lens focal length. So applying it to a 90 mm on a DR, you'd need 1/1.6*90 or about 1/150. Again, if you're skilled, rested, prepared, and braced, you can often do better, but you should know your limits and support IS.