Friday, April 12, 2019

Nikon Nikkor 80-200mm f/4.5 N Ai zoom ~ point light source comparison

I heard that spending time along the Cote d'Azur could be good for one's art.  While I make no claims to be an artist, spending time in the sun along the Mediterranean Sea inspired me to more deeply consider optics as applied to the craft of photography.

For many years I looked at just one dimension of commercially available optics - resolution.  Now I wanted to start looking at other aspects of optical performance.  For this series I look at spherical aberration (looking for under, neutral, or over correction) in out of focus rendition on subject matter behind the point of focus.

Setup -
  • Sony NEX5T, ISO 100, 2 second timer, -1 EV
  • Big Beefy Manfrotto tripod
  • Lens using with a Lens Turbo II focal reducer -
    • Nikon Nikkor 80mm - 200mm f/4.5 N Ai zoom
  • NOTE1: Lens was shot at the widest aperture only
  • NOTE2: Out of focus samples are from points _behind_ the point of focus to compare background out of focus rendition
  • RawTherapee to convert RAW files into black and white and to set the black levels
 Comparison -

If you click on the following image you can inspect it at 100 percent.

Nikon Nikkor 80mm to 200mm ~ Out of Focus Rendition

Comments -

NOTE: I feel the Lens Turbo II focal reducer adds a bit of under-corrected spherical aberration.

The Nikon Nikkor 80mm - 200mm f/4.5 N Ai zoom at 80mm and 135mm shows slight under-corrected spherical aberration in the out of focus regions.  Based on this comparison, in normal photographic use this lens at this focal length should produce a very smooth out of focus rendition.

At 200mm, this Ai zoom shows very very neutral out of focus rendition.  Under normal photographic conditions I would expect this lens at this focal length to produce extremely smooth out of focus rendition.

Resources -

For further information on how the topic of out of focus rendition, optical properties, and Nikon lens design history, please refer to the following -

A PhD thesis on the impact of "soft focus" lenses on the history of photography -

An excellent starting point for understanding out of focus rendition (I might not completely agree with his interpretations/observations, but his foundation of understanding is quite good) -

Nikon lens design histories -

Point light source discussions -

Zeiss comments on optical design -

Metabones Focal Reducer whitepaper -

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