mask during image registration

Hi All,
I have a basic question on registration using spatial object mask. Let’s say I have an image where the background is zero or close to zero and my mask is all ones, as illustrated below. When I run registration, will it take into account the surrounding voxels which are zero since the mask is 1 at these locations. This is the part I am confused on!

Hope someone can clarify this for me.

If you supply a mask of all ones, it is theoretically the same as not supplying a mask at all. Practically, the no-mask option runs faster.

But yes, if your mask is all ones, the background pixels of (near) zero intensity will be taken into account.