Lighting arrangement

[God of thunder]

Ok, this might be hard to phrase properly, but here goes.
I have a single ended 400 W MH bulp. which way is the better for balanced lighting?

Like this picture or if i turn it 90°

http://dyrarikid.is/spjall/attach.aspx/3155/DSC04201.JPG

[harlequinreefer]

Bulb perpendicular to front of tank

[God of thunder]

I´m not quite sure of what you mean by that..