Nikon Nikkor 85mm f/1.8 K pre-Ai ~ Lens Turbo II APS-C vs Full Frame

I'm continuing to work with various Nikon lenses to see if I can answer the question of which lenses when used in conjunction with a Lens Turbo II focal length reducer exhibit unacceptable field curvature.  Here is a look at an old Nikon Nikkor 85mm f/1.8 pre-Ai lens.

 

 

Another sad tale to tell, but this one has a relatively happy ending. 

I had a single coated 85mm f/1.8 H and thought I _needed_ a multi-coated version of the optic.  So I sold the H and found what I thought was a reasonably priced K.

Normally I put a lens through all the paces before I shell out the bux.  This time I checked everything _but_ the focus ring action.  Yes.  This time I got bit.  Or, should I say, I bit myself for not paying full attention to what was in play.

When I got home I realized there was sand in the focus mechanism.  It's the first time I have ever encountered such a thing. Hundreds and hundreds of lenses have passed through my hands over the years.  Yet, there I was.  Sand.  How it got there and did _not_ sand-blast the elements is beyond me.  Maybe someone dropped it in the sand when they were at the beach?  I'll never know and by now it doesn't matter.

So I did the expected and disassembled the lens, re-greased the threads, and now all is good.  Still, I should've checked more thoroughly.  I should have been able to pick up this lens for practically nothing, given the sand-packed problem.

My H version of this focal length was brilliant from Day One.  The focus was as smooth as any Nikkor I've ever own.  Further, the more I thought about it the more I liked the idea of single coated optics.  Something to give the highlights a little "sparkle."  Yes, I regret selling the H. I may have to find another one.  Someday.  But only at the "right" price.  And you can be sure I'll be checking for any consequences from trips to the beach.

Setup - 

• Sony A7 with straight-thru adapter - ISO100, 2 second timer, in-camera levels used to square the whole plot up
• Sony A6000 with Lens Turbo II focal reducer - ISO100, 2 second timer
  
• Manfrotto tripod - it's capable of securing an 8x10inch view camera, so it's sturdy enough for this
  
• Nikon Nikkor 85mm f/1.8 pre-Ai - shot at two f-stops - f/1.8 and f/8
• Rawtherapee RAW to jpg conversion - Auto-Match function (no "Capture Sharpen")
  

 

Comparison - 

Here is the scene setup.  As you can see, I moved away from using the apartment scrims (curtains) to shooting a copy of le Canard Enchaine' tapped to a flat wall.  I'm looking more carefully at field flatness, right?  Even given the all-too-often shoddy work standards around Paris, this wall is sufficiently flat for my purposes.

 

 

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

 

Comments - 

The Nikon Nikkor 85mm f/1.8 pre-Ai is sharp in the center wide open and at f/8 on both the A6000 APS-C with Lens Turbo II and the Sony A7 full frame cameras.

The extreme lower left corner of the scene at f/1.8 are equally soft between the Lens Turbo II APS-C image an the A7 full frame with straight through adapter.  In the past I've tested to see if refocusing the corners helps, and it does, but as expected the center then goes slightly out of focus. 

As with other lenses I've used in this way, the Nikkor 85mm f/1.8 K on my A6000 with Lens Turbo II in the corners at f/8 don't fully "clean up".  On the other hand, Sony A7 with straight-thru adapter f/8 images at the very corners are quite sharp, just as we would hope.

As I've said before with a few other lenses, the Lens Turbo II induced field curvature "feels" very mild in this setup.  If I applied "Capture Sharpen" to the Lens Turbo II f/8 image it would appear to be sharper than the native Sony A7 full frame image out of the camera.