[davidmanze]

Right so the deal is this:

 

    In PDAF in good light at all my lenses within reasonable bounds focus accurately.

 

 The one lens I didn't calibrate completely was the AF35mm F2D which showed back-focusing last night in night-shots.....Having re-calibrated it "today" it needed -2 and now focuses  OK.

 in PDAF. Or at least typical of how PDAF should focus.

 

Checking against CD AF using live view, I found the 35mm front focuses and will not focus to infinity!

 

    The AF50mm F1.8 also LV front focuses and will not focus to infinity.

 

   AF20mm F2.8D have not tested for LV accuracy but it will focus to infinity.

 

   AF24mm F2.8N  have not tested for LV accuracy but it also will focus to infinity.

 

  The AF85mm F1.8 have not tested for LV accuracy but it will focus to infinity.

 

   Two of my lenses therefore defy the theory that CD AF is accurate without recourse to PDAF painstaking mechanical calibration, both these lenses are very well centered and function well in PDAF on the D750.

 

  So "what the hell"" is is going on there? .....  A very good question and one that I have no real answer......other than is damned ironic in a thread about CD AF accuracies!

 

  .. I've rarely used LV on my DSLRs because of their limitations within the system, I have however used the Pentax K01 mirror-less. It had focusing issues, again it could not reach infinity, but when returned from Pentax it worked OK.                                                                                                                                                                              

 

  So here again CD AF turned round and bit me in the "derrière"  and the problem is there is nothing to adjust.

 

Never mind as Nikon's implementation of LV focusing is just too painful to use anyway!