You set blending options by double-clicking the Blend tool  or choosing Object > Blend > Blend Options. To change options for an existing blend, select the blended object first.

Spacing

Determines how many steps are added to the blend.

Smooth Color

Lets Illustrator auto-calculate the number of steps for the blends. If objects are filled or stroked with different colors, the steps are calculated to provide the optimum number of steps for a smooth color transition. If the objects contain identical colors, or if they contain gradients or patterns, the number of steps is based on the longest distance between the bounding box edges of the two objects.

Specified Steps

Controls the number of steps between the start and end of the blend.

Specified Distance

Controls the distance between the steps in the blend. The distance specified is measured from the edge of one object to the corresponding edge on the next object (for example, from the rightmost edge of one object to the rightmost edge of the next).

Orientation

Determines the orientation of blended objects.

Align to Page 

Orients the blend perpendicular to the x axis of the page.

Align to Path 

Orients the blend perpendicular to the path.

Align to Page option applied to a blend

Align to Path option applied to a blend