The perfect focal plane really gives your macros depth. The more tangent the subject is to your lens, the better the illusion of Depth of Field. Regardless of all this, you still have to nail the focus on the eye to make the photo. In combination with focal plane, this is the key. Easier said then done, but as with all Macro: practice, practice, practice. As for aperture f/14 to f/22 works well. Now which one of these apertures works Best with Low ISO, at most ISO 200, as any higher your photos degrades much more than diffraction from using apertures above f/16. I use f/16 simply because my flash is mounted on top of my camera and any aperture smaller than f/16 and lower than ISO 200, my flash requires near full strength. At f/16, ISO 200, & 1/200-sec, my flash works well at about half power and recharges as fast as I need. In all it's a combination of these three elements that will work best For you.