Ikelite special zoom and clamp set

Hi,

Being new to the DSLR scene, I have a question that may be rather obvious to readers of this forum.

What is the Ikelite special zoom and clamp set (#5509.28) used for? I am about to buy a Canon 10-22mm lens, and the lens port chart states that I need this.

I was under the impression that the lens was automatic, or does the clamp allow manual zoom and focus in addition to the automatic function.

Thanks,

Damien

Damien, the clamp allows for manual zoom....AF will be auto

Karl