Interesting patent for the aperture

[Akira]

A blog by a Japanese engineer (seemingly one of the main sources of "XXXrumors" website) posted an interesting info on the patent filed by Tamron (click the diagram to enlarge).

http://hi-lows-note.blog.so-net.ne.jp/2018-04-05

The patent is for a star-shaped aperture that keep the high frequency resolution.  What is the mechanism?  Does it work as kind of high-pass filter when it is stopped down: the aperture value stays small for the higher frequencies while it becomes larger for the lower frequencies when it is stopped down?

If I understand correctly, it would contribute to the high resolution at smaller f-numbers, but the background bokeh could be quite funky?  Also, I wonder how the DOF is affected?

[Roland Vink]

Any aperture shape which increases the edge length vs area will increase diffraction because diffraction is an edge effect - diffraction is minimised when the aperture is circular and the aperture is large.

How the star-shaped aperture might affect lower or higher frequencies is beyond me

Background bokeh would be interesting - I did exactly the same years ago by taping a star-shaped cutout to the front of my 400/5.6 lens and shooting wide open - the star effectively becomes the aperture.

The effect on DOF would be similar to using a "sink strainer" aperture sometimes used with large format lenses.

[Akira]

Roland, thank you for sharing your in-depth thoughts.

With regard to the diffraction as an edge effect, the key difference between the conventional and this star-shaped aperture is that the conventional aperture causes the diffraction in the radiating direction whereas the star-shaped aperture seems to cause the diffraction along the perimeter of the circular lens.  Would that mean the affect of diffraction is more diffused with the new aperture, which can contribute to the high frequency contrast?

[Macro_Cosmos]

Any aperture shape which increases the edge length vs area will increase diffraction because diffraction is an edge effect - diffraction is minimised when the aperture is circular and the aperture is large.

How the star-shaped aperture might affect lower or higher frequencies is beyond me

Background bokeh would be interesting - I did exactly the same years ago by taping a star-shaped cutout to the front of my 400/5.6 lens and shooting wide open - the star effectively becomes the aperture.

The effect on DOF would be similar to using a "sink strainer" aperture sometimes used with large format lenses.

The 400/5.6 is an AIS right? How is that lens 

Also I've seen people cutting out a starburst shaped cardboard and sticking it in front of a lens to mimic the effect of a "STF" type lens. Minolta's 135, Sony's 100, and the Laowa 105mm type of lenses' look. Not sure if that's what you were trying to achieve here too.

[Roland Vink]

Back then I was using a Tokina AF 400/5.6, now I use an AI 400/5.6 ED (not IF). This lens is slow to focus, and does not focus very close, but is optically good. I had both lenses for a while and compared them on a D50. The Tokina was very soft compared to the Nikkor, even on DX format. I sold the Tokina soon after   I'm not sure how my lens compares with modern options such as the AFS 80-400VR or AFS 300/4 + TC-14E.

As for why I used a star-cutout, I was playing around with bokeh effects. I took picturess at night, long exposures of a city scene. I started the exposure with the city in focus, and then pulled the focus during the exposure so the point lights went out of focus and are surrounded with a star shaped glow. I also did the same using multiple exposures, shifting focus each time to get smaller to larger stars overlaid each other. This was on film, results probably don't compare to modern standards

I did also consider a cutout with much larger number of very fine points to mimic the effects of an apodizing filter. I never tried, figured it wouldn't work very well since mechanical vignetting would make it ineffective towards the corners, and the multiple fine points would more likely lead to funky bokeh rather than the smooth effect desired.

I also thought about using a heart-shaped cutout, might be fun for wedding photography

[Akira]

Apparently, the purpose of the linked patent is not about the bokeh.  Lens baby offers such aperture blade system.

I don't mind the deviation of the discussion here at all, as I myself often cause such a deviation in others' threads.   

The patent looks interesting in that it seems to try to control he diffraction with the specially shaped aperture.