Nikkor Soft filters ~ another look

I quickly realized that using a point light source to explore how Nikkor Soft #1 and #2 filters might influence out of focus regions was insufficient.  Since the camera was out and the pears were in season, I took a series of images to illustrate optical renditions a bit more clearly.

What I wanted to see was what effect, if any, a soft filter might have on out of focus rendition comparing a neutrally corrected for spherical aberration against an under-corrected lens.

Setup -

• Sony NEX5T, ISO 100, 2 second timer, -1 EV
• Big Beefy Manfrotto tripod
• Lenses using with a Lens Turbo II focal reducer -
• Nikon Micro-Nikkor 55mm f/2.8 Ai (neutrally corrected spherical aberration)
• Nikon Nikkor 85 f/1.8 K pre-Ai (under-corrected spherical aberration)

• NOTE1: Lenses were shot at the widest aperture only
• RawTherapee to convert RAW files into black and white and to set the black levels

 Comparison -

If you click on the following images you can inspect them at 100 percent.


Nikon Micro-Nikkor 55mm f/2.8 Ai - no filter

Nikon Micro-Nikkor 55mm f/2.8 Ai - #1 Soft filter

Nikon Micro-Nikkor 55mm f/2.8 Ai - #2 Soft filter

Nikon Nikkor 85mm f/1.8 K ~ no filter

Nikon Nikkor 85mm f/1.8 K ~ #1 Soft filter

Nikon Nikkor 85mm f/1.8 K ~ #2 Soft filter


Comments -

Differences between the neutrally and under-corrected spherical aberration out of focus renditions can be subtle.  Look at the out of focus stems and the shadows on the left side of the pears.  If you study the images carefully, you will begin to see the real world effects of out of focus rendition optical corrections.

When using Nikkor Soft filters, you can see how mid-tone contrast is lowered as well as reducing resolution.  Looking carefully, again, you can begin to see how the light/dark transitions are different between the two lenses.

Here is one final example.  It was made using a Nikon Nikkor 50mm f/1.8 AiS which is under-corrected for spherical aberration in the out of focus areas behind the point of focus.  I added a Nikkor #1 Soft filter and shot the lens wide open to get the maximum out of focus rendition effect.




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

Nikkor Soft filters 1 and 2 ~ point light source comparison

Here's a question: What effect might a soft focus filter have on out of focus rendition?  I decided to have a look.

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.

More specifically, I wanted to see how Nikkor soft filters might influence the out of focus regions of under-corrected spherical aberration lenses.

Setup -

• Sony NEX5T, ISO 100, 2 second timer, -1 EV
• Big Beefy Manfrotto tripod
• Lenses using with a Lens Turbo II focal reducer -
• Nikon Nikkor 50mm f/1.8 AiS
• Nikon Micro-Nikkor 55mm f/2.8 Ai
• Nikon Nikkor 85 f/1.8 K pre-Ai

• NOTE1: Lenses were 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.



Comments -

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

The Nikon Nikkor soft filters appear to mute out of focus disk intensity.  The stronger the number filter, the stronger the effect.  In general, the basic underlying effect of spherical aberration appears to remain, such as the bright center spot that is common to under-corrected lenses.

So, what have I shown?  Not much that is readily/easily visible from the point light source comparison.  Based on experience, however, the effects of using a soft filter are more easily judged across a full image.  Even though I doubt I will significantly deepen my understanding of soft filters, I will take a look at this effect in a future post.


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

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.



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 - 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

Nikon 75-150mm f/3.5 E-series zoom ~ point light source comparision

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 E-series 75mm - 150mm f/3.5 AiS 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.



Comments -

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

The Nikon 75mm to 150mm f/3.5 AiS zoom at 75mm shows 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 100mm, this AiS zoom continues to show under-corrected spherical aberration.  Under normal photographic conditions I would expect that this lens at 100mm will continue to show a very smooth out of focus rendition.

At 150mm, this AiS 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 - 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

Nikon Nikkor 35mm f/3.5 - 105mm f/4.5 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
• Lenses using with a Lens Turbo II focal reducer -
• Nikon Nikkor 35mm f/3.5 - 105mm f/4.5 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.



Comments -

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

The Nikon Nikkor 35mm f/3.5 to 105mm f/4.5 Ai zoom at 35mm shows 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 fairly smooth out of focus rendition.

At 50mm, this Ai zoom shows under-corrected spherical aberration with a somewhat bright over-corrected spherical aberration out of focus disk edge.  Under normal photographic conditions I would expect that this lens at 50mm might product a "busy" and slightly confusing out of focus rendition.

At 105mm, this Ai zoom shows very neutral out of focus rendition.  Under normal photographic conditions I would expect this lens at this focal length to produce very 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 - 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

Nikon and Schneider 135mm lenses ~ 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 corrections) 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
• Lenses using with a Lens Turbo II focal reducer -
• Nikon Nikkor 135mm f/3.5 Ai
• Nikon Nikkor 135mm f/2.8 Q Ai'd

• Lens using a straight through adapter (ie: no focal length reduction to APS-C sensor) -
• Schneider Keuznach Tele-Xenar 135mm f/3.5 (late 1950's to early 1960's)

• 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

  Comparison -

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 135mm f/3.5 Ai lens shows under corrected spherical aberrations.  In normal photography I would expect, based on these comparisons, that there will be a very smooth and delicate (to use Nikon's own word on the topic) out of focus field rendition.

The Nikon Nikkor 135mm f/2.8 Q Ai'd lens shows under corrected spherical aberrations. The out of focus disk shows variable luminosity and is not as smooth as the f/3.5 Ai.  In normal photography I would expect, based on these, that there will be a smooth and delicate (to use Nikon's own word on the topic) out of focus field rendition.

The Schneider Kreuznach Tele-Xenar 135mm f/3.5 lens shows over corrected spherical aberrations. In normal photography I would expect, based on these comparisons, that there will be the tendency to hollow out highlights and brighter areas of the out of focus field rendition.  Some would call this a tendency toward a "harsh" 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

Nikon Nikkor 105mm f/2.5 P and Ai ~ 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 under, neutral, and over corrected spherical aberration 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
• Lenses using with a Lens Turbo II focal reducer -
• Nikon Nikkor 105mm f/2.5 P pre-Ai (early Sonnar design)
• Nikon Nikkor 105mm f/2.5 Ai (later modified Sonnar, slightly more symmetrical design)
• 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

  Comparison -

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.

Both Nikon Nikkor 105mm f/2.5 P pre-Ai and Ai lenses show under corrected spherical aberrations.  In normal photography I would expect, based on these comparisons, that there will be a very smooth and delicate (to use Nikon's own word on the topic) out of focus field 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

Nikon Nikkor 85mm, Pentax 85mm Soft ~ 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 under, neutral, and over corrected spherical aberration 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
• Lenses using with a Lens Turbo II focal reducer -
• NikonNikkor 85mm f/1.8 K pre-Ai
• Pentax 85mm f/2.2 Soft in Nikon F mount (rare? I've never seen this lens in a Nikon mount before)
• 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

  Comparison -

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 85mm f/1.8 pre-Ai shows under corrected spherical aberrations.  In normal photography I would expect, based on these comparisons, that there will be a smooth out of focus field rendition.

The Pentax 85mm f/2.2 Soft shows very strongly under spherical aberration corrections.  In normal photography I would expect, based on these comparisons, that there will be an extremely smooth and very soft rendition across the field.

There is something interesting about the Pentax soft that should be carefully noted.  The point light source remains strongly represented in the center of the out of focus disk well beyond what might be considered the normal point of focus. This is physical evidence for how a severely under-corrected spherical aberration optic can exhibit extreme depths of field, even when the lens is shot wide open.


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

Nikon Micro-Nikkor 55mm lenses ~ point light source comparison

I heard that spending time along the Cote d'Azur can 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 photography.  For many years I have looked at one dimension of commercially available optics.  Now I wanted to start looking at other aspects of optical performance.  For this series I look at under, neutral, and over corrected spherical aberration 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
• Nikon lenses using with a Lens Turbo II focal reducer -
• Nikon Micro-Nikkor 55mm f/2.8 Ai
• Nikon Micro-Nikkor 55mm f/3.5 pre-Ai
• 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

  Comparison -

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 55mm f/3.5 pre-Ai shows very very slight over corrected spherical aberrations.  In normal photography I would expect, based on these comparisons, that there will be a smooth out of focus field rendition.

The Nikon Nikkor 55mm f/2.8 Ai shows quite neutral spherical aberration corrections with just a hint of under-corrected behavior in the center of the out of focus disk.  In normal photography I would expect, based on these comparisons, that there will be an extremely smooth out of focus field rendition.

There is something interesting about the Micro-Nikkor 55mm macro lenses.  They are pretty neutral in their renderings.  These are the first (though not the only) lenses I encountered that exhibit this kind of behavior.  In practical use I loved the f/3.5 version in this regard for many of the images I made along the Cote d'Azur this winter.  Now, after these comparisons, I have mounted the f/2.8 version on a camera and have already found it's out of focus rendering to be as beautiful as I expected/hoped it would be.


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

Nikon Nikkor 24mm, (2)28mm, 35mmPC ~ point light source comparison

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 -

• 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 24mm f/2.8 Ai
• Nikon Nikkor 28mm f/3.5 pre-Ai
• Nikon Nikkor 28mm f/3.5 PC
• Nikon Nikkor 35mm f/2.8 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

  Comparison -

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 24mm f/2.8 Ai shows under-corrected spherical aberrations with just a hint of a bright ring around the edge of the image circle.  In normal photography I would expect, based on these comparisons, that there will be an ever so slightly "busy" rendition in a smooth, delicate out of focus field.

The Nikon Nikkor 28mm f/3.5 H shows strong over-corrected spherical aberration.  I find this interesting as this was designed by the man who developed the 105mm f/2.5 P and 50mm f/1.4 S Nikkors.  He clearly understood the effects of under-corrected spherical aberration on out of focus rendering.  In normal photography I would expect, based on these comparisons, that there will be a strong "soap bubble bokeh" rendition of the out of focus field.

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 slightly "busy" against a smooth out of focus field rendition.

The Nikon Nikkor 35mm f/2.8 PC (perspective control) lens shows moderate under-corrected spherical aberration with a somewhat strong bright ring around the edge of the out of focus disk.  In normal photography I would expect the lens to be "busy" against a somewhat smooth out of focus field 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

Nikon Nikkor 50mm and Micro-Nikkor 55mm ~ point light source comparison

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 -

• 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 50mm f/1.8 AiS "pancake"
• Nikon Nikkor 50mm f/2 H pre-Ai single coated
• Nikon Nikkor 50mm f/2 Ai multi-coated
• Nikon Micro-Nikkor 55mm f/3.5 pre-Ai
• 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

  Comparison -

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 50mm f/1.8 AiS "pancake" lens shows under-corrected spherical aberration from the moment the point light source goes out of focus.  The brighter ring around the outside of the image circle seems to indicate a bit of over-corrected spherical aberration as well.  In normal photography I would expect, based on these comparisons, that there will be an ever so slightly "busy" rendition in a smooth, delicate out of focus field.

The Nikon Nikkor 50mm f/2 H pre-Ai single coated lens shows rather strong under-corrected and over-corrected spherical aberration.  In normal photography I would expect, based on these comparisons, that there will be a somewhat strong "busy" rendition set against a smooth, nuanced out of focus field.

The Nikon Nikkor 50mm f/2 H Ai multi-coated lens shows rather strong over-corrected spherical aberration.  In normal photography I would expect, based on these comparisons, that there will be a strong "busy" rendition of an out of focus field.  It would expect strong "soap bubble bokeh" rendition.

The Nikon Micro-Nikkor 55mm f/3.5 pre-Ai single coated lens shows neutrally corrected spherical aberration.  In normal photography I would expect, based on these comparisons, that there will be a smooth out of focus field.


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