I'm a bit confused with this one. When the D800 and D800e were launched, I understood the difference to be that the 'e' model had no AA filter. However, I've recently read that it actually has 2 of them, with one of them cancelling the other out. There was, though, no explanation for the reason why 2 filters are used to achieve the same effect as having no filter at all. Surely 2 filters, even cancelling each other out, permit less light to reach the sensor, which is definitely a detrimental quality as far as I can see. Are 2 used rather than none to protect the sensor from dust, maybe? Would appreciate someone explaining Nikon's reasoning for 2 filters, please.
They have to pass the light through the same amount of glass as the 'non-E' version, otherwise they'd possibly have to do more radical re-engineering including re-positioning the sensor. Instead of using horizontal then vertical splitting filters, they use a horizontal splitting then a horizontal joining filter - so the optical path of the light is very similar but no antialiasing blur occurs.
It's good to have a glass/filter slightly in front of the sensor, as the further from the sensor the filter is, the softer the shadow a dust particle will cast (at wide apertures). With no filter at all the effect of dust would be a lot more visible.