Nikon Nikkor 50mm f/1.8 AiS ~ Yet Another Look

Having looked at Nikon Nikkor 24mm f/2.8 Ai and an old Nikon Nikkor-O 35mm f/2 for field flatness on full frame Sony A7, here is a look at a Nikon Nikkor 50mm f/1.8 AiS "pancake".

 

 

Questions of field flatness arose when I used a Nikon Nikkor 24mm f/2.8 Ai in conjunction with a Lens Turbo II focal reducer on Sony APS-C mirrorless cameras.  I couldn't find a way to get that combination sharp in the corners, even stopped down and I couldn't believe that Nikon would ever design a lens with that much curvature.  

After moldering around for four or five years, the idea finally hit me that maybe the problem was the Lens Turbo II focal reducer and not the Nikkor.  Duh.

For completeness, I mounted a Nikon Nikkor 50mm f/1.8 AiS "pancake" on my low-mileage Sony A7 using a straight-thru adapter and pointed the lens at a fine-detailed subject.  The fine-detailed subject just happened to be our daylight back-lit apartment gaze curtains.

Setup - 

• Sony A7 - ISO50, 2 second timer, in-camera levels used to square the whole plot up
• Manfrotto tripod - it's capable of securing an 8x10inch view camera, so it's sturdy enough for this
  
• Nikon Nikkor 50mm f/1.8 pre-Ai single coated - shot from f/1.8 through f/8
• Rawtherapee RAW to jpg conversion - Auto-Match function, but nothing further (ie: NO Capture Sharpening)

Comparison - 

Here is the scene setup.  It's just a pair of closed gaze scrims in our apartment.  The details are interestingly small, so therefore useful for this kind of "wee look-see."  The center section, upper left corner, and lower right corners were used in the comparison.

 

 

[As always, click on the image and look at it to 100percent file size to see whatever there is to be seen.]

 

 

Comments - 

Wide open the 50mm Nikkor is a bit soft.  What was important to me was to confirm there was a similar level of softness across the field from the center all the way to the edges.  This appears, in fact, to be the case.

From f/2.8 on down through f/8 this little "pancake" lens is plenty "sharp" to my eyes.

I believe the Nikon Nikkor 50mm f/1.8 AiS "pancake" is the same design as the Nikon 50mm f/1.8 series-E and the more recent Nikon Nikkor AF-D 50mm f/1.8.

Nikon's "Thousand and One Nights" says -

"...the Series E 50mm f/1.8, sold in some regions including the U.S., and the AI Nikkor 50mm f/1.8S were actually sister lenses designed with the same basic optics, but different outward appearance and coatings...

What's more the same basic optical design was reborn as the AI AF Nikkor 50mm f/1.8S (coatings and such were modified), and is still available today (2016) in the AI AF NIKKOR 50mm f/1.8D. When this lens was reborn as an AF lens, it lost its slim, pancake design, but its rendering characteristics remain the same..." 

I've owned several series-E 50mm f/1.8 lenses over the years, and they performed for me the same way the AiS Nikkor version does.  All were/are slightly soft wide open and with a pleasing out of focus rendition.

This compares with my experience of using a Nikkor f/2 pre-Ai and Ai 50mm.  These are wickedly sharp wide open, but the out of focus rendition can be very harsh "soap bubble."  For those who believe that lens formulas hold the secret to great out of focus performance, both the harsh f/2 and beautiful f/1.8 50mm lenses are the exact same 6 element, 4 group plasmat layout.  The difference is in the calculation of the curves of the various lens elements.

Coming back to the original question, I don't recall seeing field curvature issues with the 50mm Nikkor f/1.8 AiS lens when combined with a Lens Turbo II focal reducer.  So, for whatever reason, there might not be the set of circumstances that lead to the effects I saw clearly with a Nikkor 24mm with a Lens TurboII.

In any event, this confirms the 50mm Nikkor is respectably flat field across the field and very sharp when shot on full frame.