Second, those AM eyes (the two large central eyes) have visual fields that do indeed overlap. (Just look at them! Though a problem could be at what object distance.) More to the point, Land goes on to state, “The eye tubes pivot about the regions immediately behind the lenses, and a set of six eye muscles permits each retina to move vertically, laterally or obliquely in one plane, and in addition the retinae can be rotated about the visual axes.” That is, jumping spiders can change the field of view – even to the point of rotating it – of the their AM eyes not by moving the entirety of the eyes (which presents problems for animals with exoskeletons), but instead by moving the retinae behind the lenses.

In a section of his paper entitled, “Why several layers?” Land even anticipated this usage of the separate layers:
“(a) The several receptor layers act in lieu of a focusing system, the animal using one or another layer to examine objects at different distances from it.”
or
“(b) Each receptor layer contains a different photopigment and is situated in a plane containing the best image for light of the wavelength of maximum absorption of that pigment.”

It is therefore quite likely that jumping spiders possess more than one means of assessing the distance of objects (i.e. via blur, as well as potentially by differential movement of near and far objects, and/or stereoscopic comparison).

The photo at the top is my pallid attempt to imitate the style of artist Thomas Shahan, whose work remains the gold-standard in the, um, burgeoning field of spider portraiture:

Real-life spiderman