focal length for a manual lens

Hi, I got hold of a sigma 70-210mm manual focus.

Now its mounted on the body and when I switch on the camera, it's asking for the focal length. What would be the most appropriate focal length for a lens of those dimensions?

I believe that this is only for the Shake Reduction system.

thanks

ideally put the focal length you are going to use, or failing that i have read a recomendation to use the shortest...ie 70.

Putting a longer focal length in will over compensate your shots at the short end of your zoom.

It is for the SR system you're quite right.

With a zoom lens the best way would be to input a focal length closest to that you intend shooting at; ie if you were going to be using it mainly at the long end then input 200mm, if at the wide end then input 70mm. Some folk use a length somewhere in the middle but it really depends on your own style of shooting so experiment and see what gives you the best results.

Thanks, so it sounds like it's not a big issue then if its not set correctly.

cheers

Well the camera can only compensate for shake if it knows what length of lens its compensating for, otherwise it'll over or under compensate with the result being the SR system is less effective than it possibly could be.

In the grand scheme of things no, it's not a really big issue.