Returning home after passing a winter in the south I am inspired to continue my look into point light source in-focus, out of focus comparisons.
Setup -
If you click on the following image you can inspect it at 100 percent.
Comments -
NOTE: I feel the Lens Turbo II focal reducer adds a bit of under-corrected spherical aberration.
The Nikon Nikkor 28mm f/2.8 Ai shows under-corrected spherical aberrations with just a moderately strong bright ring around the edge of the image circle. In normal photography I would expect, based on these comparisons, that there will be a hint of a "busy" rendition in a smooth, delicate out of focus field.
The Nikon Nikkor 28mm f/3.5 H shows stronger over-corrected spherical aberration with a fairly bright edge ring on out of focus disks. The center, as with it's brother lens the f/2.8, shows under-corrected spherical aberration. In normal photography I would expect, based on these comparisons, that there will be a somewhat confusing rendition of the out of focus field, mixing the two aberration types as this lens does.
The Nikon Nikkor 28mm f/3.5 PC (perspective control) lens shows moderate under-corrected spherical aberration with a hint of a bright ring around the edge of the out of focus disk. In normal photography I would expect the lens to be a hint of a "busy" field against a smooth, delicate 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 - http://research-repository.st-andrews.ac.uk/handle/10023/505
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) - http://jtra.cz/stuff/essays/bokeh/
Nikon lens design histories - https://imaging.nikon.com/history/story/
Point light source discussions - https://www.dpreview.com/forums/thread/4031515
Zeiss comments on optical design - https://lenspire.zeiss.com/photo/en/article/how-does-zeiss-define-bokeh-an-interview-with-dr-stefan-ballmann
Metabones Focal Reducer whitepaper - https://www.metabones.com/assets/a/stories/Speed%20Booster%20White%20Paper.pdf
Setup -
- Sony NEX5T, ISO 100, 2 second timer, +1 EV
- Big Beefy Manfrotto tripod
- Nikon lenses using with a Lens Turbo II focal reducer -
- Nikon Nikkor 28mm f/2.8 Ai
- Nikon Nikkor 28mm f/3.5 H pre-Ai
- Nikon Nikkor 28mm f/3.5 PC
- NOTE1: Lenses were shot at their widest apertures 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
If you click on the following image you can inspect it at 100 percent.
Comments -
NOTE: I feel the Lens Turbo II focal reducer adds a bit of under-corrected spherical aberration.
The Nikon Nikkor 28mm f/2.8 Ai shows under-corrected spherical aberrations with just a moderately strong bright ring around the edge of the image circle. In normal photography I would expect, based on these comparisons, that there will be a hint of a "busy" rendition in a smooth, delicate out of focus field.
The Nikon Nikkor 28mm f/3.5 H shows stronger over-corrected spherical aberration with a fairly bright edge ring on out of focus disks. The center, as with it's brother lens the f/2.8, shows under-corrected spherical aberration. In normal photography I would expect, based on these comparisons, that there will be a somewhat confusing rendition of the out of focus field, mixing the two aberration types as this lens does.
The Nikon Nikkor 28mm f/3.5 PC (perspective control) lens shows moderate under-corrected spherical aberration with a hint of a bright ring around the edge of the out of focus disk. In normal photography I would expect the lens to be a hint of a "busy" field against a smooth, delicate 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 - http://research-repository.st-andrews.ac.uk/handle/10023/505
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) - http://jtra.cz/stuff/essays/bokeh/
Nikon lens design histories - https://imaging.nikon.com/history/story/
Point light source discussions - https://www.dpreview.com/forums/thread/4031515
Zeiss comments on optical design - https://lenspire.zeiss.com/photo/en/article/how-does-zeiss-define-bokeh-an-interview-with-dr-stefan-ballmann
Metabones Focal Reducer whitepaper - https://www.metabones.com/assets/a/stories/Speed%20Booster%20White%20Paper.pdf
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