From Nikon support:
After the move to G (no diaphragm control on the lens when mounted), now the move to E takes away the mechanical link to the diaphragm.
The evolution of lenses was first one of adding (communication with the camera and control from the camera) now to remove from the lens some functionality (control from the lens) to not have it double anymore.
I personally like D lenses which have both options, but the new lenses will require newer bodies, however the E lenses have design advantages (and Canon has done it since ages).
My personal issue is with the Nikon 300mm Nikkor f4E, which is a lot more portable but will not work on my D70s (or mechanical adaptor to the Sony A7 series).
[h=1]What are E type lenses?[/h]Answer ID 19485|Published 08/13/2015 04:41 PM|Updated 08/17/2015 10:07 AM
Electromagnetic Diaphragm Mechanism
An electromagnetic diaphragm mechanism in the lens barrel provides highly accurate electronic diaphragm or aperture blade control when using auto exposure during continuous shooting. With conventional D/G type lenses, the diaphragm blades are operated by mechanical linkage levers.
Nikon D2-series, D1-series, D200, D100, D90, D80, D70-series, D60, D50, D40-series, D3000, and film SLR cameras will not communicate aperture information electronically and cannot be used. For up to date information on which cameras may be used, please view the User manual of the E lens. These new E type lenses are CPU controlled, and not to be confused with 1980's Series-E lenses, which were manually controlled.
After the move to G (no diaphragm control on the lens when mounted), now the move to E takes away the mechanical link to the diaphragm.
The evolution of lenses was first one of adding (communication with the camera and control from the camera) now to remove from the lens some functionality (control from the lens) to not have it double anymore.
I personally like D lenses which have both options, but the new lenses will require newer bodies, however the E lenses have design advantages (and Canon has done it since ages).
My personal issue is with the Nikon 300mm Nikkor f4E, which is a lot more portable but will not work on my D70s (or mechanical adaptor to the Sony A7 series).