Does a zoom lense always need tripod ?

Stu Brennan wrote:

IIRC there was an old rule of thumb from back in the 35mm film days. The shutter speed should be, according to the rule, faster than "1 over the focal length". If you are at 500mm, for instance, the shutter should be at 1/500 or faster.

You do RC, but the ROT needs to include the crop factor to get the 35mm equivalent focal length (EFL), so your example becomes 1/(500x1.6) = 1/800.

If you can't manage that, then you need a support or a tripod.

That's the crucial thing - the ROT is a gross approximation, and you have to do some testing to know what you (your own self) can get away with. That testing also has to take into account your purpose, for instance, you need much faster shutters for large images of birds than you do for small images of sunsets.

You can test it by taking 10 shots at 1/2EFL, then 1/EFL, 2/EFL, 4/EFL... If you can consistently get say 90% sharp shots at a particular ratio, then that can be your personal ROT.

I assume that today's image stabilization would allow you to cheat that a little, but probably not much

Actually quite a bit. I've found Canon's claims to be accurate, for instance, if they say IS is worth 3-4 steps, then I can confidently go 3 steps longer on the shutter.

I don't know about the 55-250 STM, but the older 55-250s needed a good second for the IS to settle, so you need to take a deliberate pause with those lenses.