Roto Till Time ~ mid-Till ~ part Five

The Sony 35mm f/2.8 FE ZA is a very fine optic. So I naturally thought about it as a replacement for the Sigma 30mm f/2.8 EX DN I have for the APS-C cameras that live here.

Except, it might not be as easy as I first hoped.  Comparing the Sony ZA to the Sigma was pretty easy.  But...

The Sony 35mm ZA failed repeatedly to focus accurately on this day and under these circumstances on an A6000.  It focused and still focuses correctly on an A7, a NEX-7, and a NEX-5T.  

To arrive at some meaningful understanding of what's going on, I manually focused the Sony to see if I could isolate the problem.

 

 

I like using le Canard as my comparison subject.  The typeset print gives a nice crisp transition from light to dark.

Setup ~ 

• Cameras - 
• Sony A7
• Sony A6000
• Lenses - 
• Sony 35mm f/2.8 ZA
• Sigma 30mm f/2.8 EX DN 
• Sigma 19mm f/2.8 EX DN
  
• Bogen tripod
  

• RawTherapee to snug up the curves, without "Capture Sharpen"
  

Comparison ~

As always, click on the image and enlarge to 100percent to see whatever there is to be seen.

 

Comments ~

Straight away it's clear that the Sony and Sigma lenses, with one camera/lens combination exception, do what they're supposed to.  That is, they are sharp from wide open across the field.

 

I also confirmed that my ability to manually focus these lenses in general is not as good as cameras AF systems.  Here is the reason I've decided to unload my beautiful manually focused old Nikon Nikkor lenses.  I feel the need for automated support for these old eyes.

Looking at the case of the Sony A6000 and 35mm ZA, the "missed focus" is evident wide open and at f/4.  By f/5.6 things clean up pretty well.  Looking closely at the AF series from this combination it "feels" to me like the actual focus point isn't all that far off the intended point.  

 

Am I making too much of this?  Maybe.  Maybe not.  

 

I've since gone back and tried this camera/lens combination on other subjects and it seems to focus correctly.  What happened during the comparison shown here?  I have no idea.  All I can say is that I turned the camera on and off several times and the contact points for the communications between the lens and camera looked to be OK.

I guess I'll have to file this under the heading of "Bizarre Unknowns."

 

 

Sony NEX-5T with good for nothing 16mpixel sensor,
Sigma 30mm f/2.8 EX DN at f/4
Handheld.
Not half bad for a lens and camera that
are no longer made...

As for the comparison of the Sony 35mm ZA and Sigma 30mm on APS-C, the original reason for doing this comparison, can you see any difference between them?  I can't.

If for only the reason of uncertainty of focusing the ZA on the A6000, perhaps I'd do best to hold onto the old jewel Sigma 30mm.  The old Sigma is a great little optic.  

 

Why did Sigma stop making them?  Maybe there's no market for small/light/inexpensive/sharp lenses?  No.  I don't believe that.  Not for a moment do I believe that.