Wednesday, April 13, 2016

30 to 85mm lens comparison ~ with and without Zhongyi Lens Turbo II

After returning from Lisbon I found I've not be inspired by much.  So, I hauled out another page of newsprint, taped it a wall and compared another bunch of lenses.

The setup -
  • Sony A6000, 100ISO, AWR converted in Sony's software
  • Big Beefy Manfrotto tripod
  • Sigma 30mm f/2.8 EX DN E as the control optic - it's sharp sharp sharp
  • Old Nikon manual focus lenses
    • 35mm f/2 Ai
    • 50mm f/1.8 E-series
    • 50mm f/1.4 pre-Ai (Ai adapted)
    • 55mm Micro-Nikkor f/3.5
    • 85mm f/1.8 K Ai (multi-coated)
    • 85mm f/1.8 H pre-Ai (Ai adapted)
    • 85mm f/2 Ai
  • Zhongyi Lens Turbo II focal reducer
The goal is to see under normal contrast conditions what effect the Lens Turbo II had on optical performance.  I'd shot a comparison along similar lines about a year ago, but that was in a low contrast situation and I was at that time really just looking at the rendition of out of focus areas.

Look at the following at 100 percent to see the differences in performance.  The rows surrounded by red fuzzy bands are the lenses shot without the Zhongyi Lens Turbo II (even though the wording next to these rows says Zhongyi) - the Zhongyi row is the one above the red fuzzy outlined row.  The distance to the target was adjusted by 1.5x to keep the image size equal to those shot with the focal reducer.

Zhongyi LensTurbo II compared to native optics
Observations -
The Zhongyi Lens Turbo II neither improves nor degrades the optical performance of the Nikkor lenses I compared.  If a lens suffers from spherical aberrations when shot wide open, then images made with and without the focal reducer appear equally soft.  Similarly, once an image becomes sharp, both images are equally sharp.

There's one thing that is underscored by performing this comparison and that is that by f/4 every lens performs equally well.  Said another way, my super sharp Sigma 30mm f/2.8 EX DN E is really no better than any of the old, and in some cases very old, Nikon manual focus lenses after f/4.

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