4 ms·

> Odd bokeh was one of the risks of adding a mechanical aperture, and bokeh is very often weirdest at the first or second down from open. Why? Where can I read

by gyomu 8d ago

> Odd bokeh was one of the risks of adding a mechanical aperture, and bokeh is very often weirdest at the first or second down from open. Why? Where can I read/learn more about this?

robotmay 8d ago
This is usually due to the blade shape and quantity I believe. The aperture is most likely to be less circular on the widest apertures after fully open unless you have quite a lot of aperture blades, as the curve to make a rounder aperture is usually applied more towards the tip of the blade, and you're only seeing the base of the blades at wider apertures. That varies a lot by aperture design, however - if you have the more banana-shaped blades where the retaining pin and pivot pin are at opposite ends (like in a Yashica TLR) then I believe they can maintain a more consistent curve along the length. Those also suck massively to reassemble, but that's a different story. I haven't seen a diagram of how the aperture in this new iPhone is designed yet. There's a lot of different ways to do it, with lots of odd shape possibilities.
- dofm 8d ago
  > This is usually due to the blade shape and quantity I believe. Also because of things like angle of incidence? The purely round lens will generally have nice round (or at least cats-eye) bokeh across the frame with an edge that degrades softly as a result of aberration, so beams of light from different angles tend to blur into each other. As soon as you get aperture blades, you lose that soft edge, get contrast but also a lot of competing shape influences at different angles. They will tend towards more rounded shapes as you stop down more. And that is putting aside that some aperture shapes are just really insane when they are nearly wide open, right? (Konica 40mm f/1.8 AR I am looking at you with your shuriken bokeh) > I haven't seen a diagram of how the aperture in this new iPhone is designed yet. There's a lot of different ways to do it, with lots of odd shape possibilities. Not a diagram but one closeup photo: https://petapixel.com/2026/09/19/apple-explains-why-the-iphone-18-pro-has-a-variable-aperture/ https://petapixel.com/2026/09/19/apple-explains-why-the-ipho... and an animation: https://petapixel.com/2026/09/09/iphone-18-pro-has-apples-fastest-lens-yet-thanks-to-variable-aperture/ https://petapixel.com/2026/09/09/iphone-18-pro-has-apples-fa... Six blades with a slightly rounded hook in them by the look of it. Very noticeable sun stars at f/1.8, nice looking results at f/2.8. Absolutely insane mechanical challenge and assembly challenge.
  - robotmay 8d ago
    Ooh yeah I love those weird shapes nearly wide open. I found a lens that had a torx bit shaped aperture the other day, I'll have to fish that out and see what it looks like in an image. Lots of compact cameras have a diamond/square-ish hole, notably the Minox 35 range from what I can recall. Edit: just saw your update with the photos of the mechanism. Wow that's impressive miniaturisation. The hexagonal shape looks surprisingly good. I wonder what's causing the odd effects in the OP. I have noticed in the past that iPhone cameras produce square specular highlights through tree foliage, so I wonder if it's an extension of that oddity.
    - dofm 8d ago
      Yes that mechanism only has two blades! They are sort of sickle-shaped. (Presumably gave the Soviet cloners a chuckle) I found myself looking at it when I was considering making a DIY aperture for my DIY lenses. (I've personally settled on swappable Waterhouse stops for now but I might fit an eBay microscope aperture, many of them have loads of blades). Oh and now I'm going to end up looking on eBay for a Minox 35ML or 35GT again. Seriously, never do this while logged in; Minox 35 sellers may be among the most desperate I've ever seen in terms of sending you offers, it's relentless.
      - robotmay 8d ago
        Haha there's certain camera models that are very prone to that. Some of the Pentacon M42 lenses are worth a look if you want an unholy amount of blades - I have a 135mm f/2.8 sat around that has like 15 blades or something daft. Coincidentally I think I have a non-working 35GT in my market stall (https://camerasetc.wales https://camerasetc.wales), so if you want a project drop me an email as I'll send it to you for the cost of postage. I have too much in my repair backlog and those things are fiddly little bastards at the best of times :D
        dofm 8d ago
        Oh I think I have seen your website before! I too have too much clutter so I will have to turn down your kind offer but I will peruse your sites and I may ping you a note sometime about a particular lens I have been looking for — quite a random cheap old one I regret parting company with. (I'm in Kent but I have a friend in Cardiff and if my wallet does not protest I may pop in on your stall)
Melatonic 7d ago
It's not due to the aperture blades. It's due to the amount of spherical aberration in the lenses. Professional camera lenses carefully control this. It's actually one of the only intentional "flaws" added to lens. Technically bokeh with a slight ring on it (on point lights) usually results in a tack sharp lens. You can see this in most macro lenses. Portrait lenses are sort of the opposite - they want super smooth bokeh (point light sources in the blurred out of focus area will have a nice gradient that is soft and gradually drops off toward the edges). This results in a lens that has slightly less sharpness on the in focus portion. It's not that noticeable though on a great lens. Most lenses are a balance. When shooting professional cinema many lenses are intentional chosen for their bokeh qualities. "Nervous" bokeh is more on the side of rings and is often found on older Russian and East German glass. There are two lenses where the amount of spherical aberration is not baked into the lens. They were made by Nikon called "Defocus Control". The 105mm 2.0 DC and slightly older 135mm 2.0 DC both have a second ring that looks another aperture ring but allows adjustability of the spherical aberration from "nervous" to "smooth". They were marketed poorly and misunderstood but are some of the best glass you can get - they test insanely well and have huge flexibility.
- dognotdog 7d ago
  > The 105mm 2.0 DC and slightly older 135mm 2.0 DC [...] I almost never change the defocus control on the 135/2.0 from neutral, yet I believe the lens makes it almost impossible to take a bad portrait. The only reason to keep a DSLR around instead of a mirrorless is that this lens has an old-school camera driven auto-focus, which Nikon's F-to-Z adapters don't support. While manually focusing that lens can be done, the shallow depth of field makes it very challenging for moving subjects.
  - Melatonic 7d ago
    It's definitely worth messing with. The reason it has a F and R side (with aperture markings) is that a lens will be optimised to either provide ideal bokeh at close or long focus (long focus bokeh being things blurred in the foreground closer to the camera). Try setting it for example to F 2.8 real aperture and then I believe move the DC ring to R 2.8 or 4 and you should get a very pleasant creamy blur. Or for a slightly sharper portrait move to neutral or R 2.0

by gyomu 8d ago

> Odd bokeh was one of the risks of adding a mechanical aperture, and bokeh is very often weirdest at the first or second down from open. Why? Where can I read/learn more about this?

robotmay 8d ago

This is usually due to the blade shape and quantity I believe. The aperture is most likely to be less circular on the widest apertures after fully open unless you have quite a lot of aperture blades, as the curve to make a rounder aperture is usually applied more towards the tip of the blade, and you're only seeing the base of the blades at wider apertures. That varies a lot by aperture design, however - if you have the more banana-shaped blades where the retaining pin and pivot pin are at opposite ends (like in a Yashica TLR) then I believe they can maintain a more consistent curve along the length. Those also suck massively to reassemble, but that's a different story. I haven't seen a diagram of how the aperture in this new iPhone is designed yet. There's a lot of different ways to do it, with lots of odd shape possibilities.

dofm 8d ago
> This is usually due to the blade shape and quantity I believe. Also because of things like angle of incidence? The purely round lens will generally have nice round (or at least cats-eye) bokeh across the frame with an edge that degrades softly as a result of aberration, so beams of light from different angles tend to blur into each other. As soon as you get aperture blades, you lose that soft edge, get contrast but also a lot of competing shape influences at different angles. They will tend towards more rounded shapes as you stop down more. And that is putting aside that some aperture shapes are just really insane when they are nearly wide open, right? (Konica 40mm f/1.8 AR I am looking at you with your shuriken bokeh) > I haven't seen a diagram of how the aperture in this new iPhone is designed yet. There's a lot of different ways to do it, with lots of odd shape possibilities. Not a diagram but one closeup photo: https://petapixel.com/2026/09/19/apple-explains-why-the-iphone-18-pro-has-a-variable-aperture/ https://petapixel.com/2026/09/19/apple-explains-why-the-ipho... and an animation: https://petapixel.com/2026/09/09/iphone-18-pro-has-apples-fastest-lens-yet-thanks-to-variable-aperture/ https://petapixel.com/2026/09/09/iphone-18-pro-has-apples-fa... Six blades with a slightly rounded hook in them by the look of it. Very noticeable sun stars at f/1.8, nice looking results at f/2.8. Absolutely insane mechanical challenge and assembly challenge.
- robotmay 8d ago
  Ooh yeah I love those weird shapes nearly wide open. I found a lens that had a torx bit shaped aperture the other day, I'll have to fish that out and see what it looks like in an image. Lots of compact cameras have a diamond/square-ish hole, notably the Minox 35 range from what I can recall. Edit: just saw your update with the photos of the mechanism. Wow that's impressive miniaturisation. The hexagonal shape looks surprisingly good. I wonder what's causing the odd effects in the OP. I have noticed in the past that iPhone cameras produce square specular highlights through tree foliage, so I wonder if it's an extension of that oddity.
  - dofm 8d ago
    Yes that mechanism only has two blades! They are sort of sickle-shaped. (Presumably gave the Soviet cloners a chuckle) I found myself looking at it when I was considering making a DIY aperture for my DIY lenses. (I've personally settled on swappable Waterhouse stops for now but I might fit an eBay microscope aperture, many of them have loads of blades). Oh and now I'm going to end up looking on eBay for a Minox 35ML or 35GT again. Seriously, never do this while logged in; Minox 35 sellers may be among the most desperate I've ever seen in terms of sending you offers, it's relentless.
    - robotmay 8d ago
      Haha there's certain camera models that are very prone to that. Some of the Pentacon M42 lenses are worth a look if you want an unholy amount of blades - I have a 135mm f/2.8 sat around that has like 15 blades or something daft. Coincidentally I think I have a non-working 35GT in my market stall (https://camerasetc.wales https://camerasetc.wales), so if you want a project drop me an email as I'll send it to you for the cost of postage. I have too much in my repair backlog and those things are fiddly little bastards at the best of times :D
      - dofm 8d ago
        Oh I think I have seen your website before! I too have too much clutter so I will have to turn down your kind offer but I will peruse your sites and I may ping you a note sometime about a particular lens I have been looking for — quite a random cheap old one I regret parting company with. (I'm in Kent but I have a friend in Cardiff and if my wallet does not protest I may pop in on your stall)

Melatonic 7d ago

It's not due to the aperture blades. It's due to the amount of spherical aberration in the lenses. Professional camera lenses carefully control this. It's actually one of the only intentional "flaws" added to lens. Technically bokeh with a slight ring on it (on point lights) usually results in a tack sharp lens. You can see this in most macro lenses. Portrait lenses are sort of the opposite - they want super smooth bokeh (point light sources in the blurred out of focus area will have a nice gradient that is soft and gradually drops off toward the edges). This results in a lens that has slightly less sharpness on the in focus portion. It's not that noticeable though on a great lens. Most lenses are a balance. When shooting professional cinema many lenses are intentional chosen for their bokeh qualities. "Nervous" bokeh is more on the side of rings and is often found on older Russian and East German glass. There are two lenses where the amount of spherical aberration is not baked into the lens. They were made by Nikon called "Defocus Control". The 105mm 2.0 DC and slightly older 135mm 2.0 DC both have a second ring that looks another aperture ring but allows adjustability of the spherical aberration from "nervous" to "smooth". They were marketed poorly and misunderstood but are some of the best glass you can get - they test insanely well and have huge flexibility.

dognotdog 7d ago
> The 105mm 2.0 DC and slightly older 135mm 2.0 DC [...] I almost never change the defocus control on the 135/2.0 from neutral, yet I believe the lens makes it almost impossible to take a bad portrait. The only reason to keep a DSLR around instead of a mirrorless is that this lens has an old-school camera driven auto-focus, which Nikon's F-to-Z adapters don't support. While manually focusing that lens can be done, the shallow depth of field makes it very challenging for moving subjects.
- Melatonic 7d ago
  It's definitely worth messing with. The reason it has a F and R side (with aperture markings) is that a lens will be optimised to either provide ideal bokeh at close or long focus (long focus bokeh being things blurred in the foreground closer to the camera). Try setting it for example to F 2.8 real aperture and then I believe move the DC ring to R 2.8 or 4 and you should get a very pleasant creamy blur. Or for a slightly sharper portrait move to neutral or R 2.0