circular aperture blades, bokeh

Discussion in 'Leica and Rangefinders' started by leslie_cheung, Nov 8, 2002.

  1. i notice the new canon L lense have "circular blades" in the lens.
    to the eos users here, do they have more pleasing bokeh? in general,
    is there a consensus here that more blades equals better bokeh? i
    noticed the bokeh lenses have more aperture blades, but then the
    leica asph and the c/v 50f1.5 are not known to have pleasing bokeh
    though very sharp.

    is there an objective way to achieve discs as oppose to donuts??
    is that the reason for the circular blades in the new canons? or is
    it gimmick and myth?
     
  2. Circular blades is only one way to achieve a less distracting OoF image.

    If you have say... 10 circular blades, versus 6 polygonal blades... your OoF specular highlights will be round as opposed to hexagonal.

    On the other hand... some lenses just don't seem to give a pleasing bokeh no matter what, circular blades and all.

    Its a combination of lens type, its optical design and the blades that all somehow magically come together and form that smooth pleasing OoF image.
     
  3. My understanding is that its a way to correct 'bad' bokeh, rather than get good bokeh, which is more a result of the inherent lens design. Likewise, the number of blades don't make much difference. For me though, all those blades on an old 2.8 Elmar are wonderful to look at if nothing else.
     
  4. Steve is right, arperture blades invluence the shape of the OOF circles, the characteristics of the bokeh are deriving from the optical formulae. Arperture blades arent that important to me, i use a lens wide open if the blades dont provide a perfect round shape....

    Apart form diffraction and all kinds of abberations which can invluence the quality of the bokeh there are generally 3 kinds of bokeh.

    1. Donut shape, bad looking bokeh. Very distracting looks like a pile of rubble.

    2. Disc shape, perfect gradtions, not distracting at all, flat background OOF area. Optical designers wet dream.

    3. Sphere shape, gaussian blurred edges, looks cloudy and soft, kinda embracing the subject. The blurred edges occur more in complex optical designs like zoom lenses, they are a result of reflected light in the lens.

    I didnt come up with these 3 groups myself off course, they were introduced by Ken Rockwell(http://www.kenrockwell.com/tech/bokeh.htm) i think they are a great aid to analysing bokeh characteristics so please read his page about bokeh.

    Allthough optical designers aim for the neutral disc shape bokeh, in practical terms there are alot of gradations between these types. To make things even more complex, most lenses are highly corrected in the centre and less corrected in the edges. This way the angle in which the light is reflected into the lens is also important. Still enjoying this?

    Personally i love the disc(neutral) bokeh type, it renders great depth in a picture if used right. Best bokeh tool? In Leica lenses i would vote for the 35mm Lux, the background and subject(its not about the bokeh its about the subject!) are sometimes in such perfect harmony that its allmost 3D.

    Im pretty sure the photographer takes the pictures, please dont think you need the 35mm Lux to get good bokeh, its just a tool......

    Greetings,
     
  5. I posted this picture on one of the above threads about Nocti Bokeh, then realized it related to your "circular OOF highlights" thread here so I thought to post the image to demonstrate very round ones that the Nocti produces. One of the things I do not like about my Zeiss lenses for Hasselblad are the Pentagram OOF highlights. They look like a Chrysler logo or some occult symbol. HATE it!
    0040WM-10144584.jpg
     
  6. I posted this a long time ago, but here are two photos made with similar focal length lenses (90mm Elmarit M and 105mm f/2.5 Nikkor) both shot at f/4.0. The photos have a similar sharpness and there is not one that jumps ahead of the other for the most part... except for the rendition of the highlights. The Nikkor has only 6 blades and forms a simple hexagonal shape aperture, while the Leica Elmarit with more blades forms a more circular shape. If you look at the out of focus highlights, these shapes are apparent. Whether or not this is important is open to discussion, but hexagons can compete for attention in some situations.
    Just a note... these two photos are not part of any test, or even good photography for that matter. They are out-takes from a series done over several days. I saw this effect over and over again, and chose two representative images only because of the similar composition.
    Aperture blade shape and highlight bokeh effect
     
  7. One other thing about this... at full aperture, the opening is round so this is a bit moot. This is a shot made with that same 105mm lens (as above) but at f/2.5 rather than f/4.0. No hexagons, just nice soft round highlight blurs. I post this non-Leica shot just to demonstrate how the same lens with bad hexagonal highlights can have good blurs while wide open... possibly confirming the importance of aperture shape. Close the aperture down just a little, and the blur takes on the shape of the blades.
    0040Y1-10145284.JPG
     
  8. Albert; which 105mm F2.5 Nikkor do you own with only 6 aperture blades?

    Is is a LTM chrome or LTM black, a pre 1971 AI F nikkor Sonnar type, a post 1971 pre AI Gauss type, a AI type of the mid 1970's , or a AIS Nikkor ??????????

    I used a 105mm F2.5 Nikkor for the F in the 1970's. It had 7 blades and was a pre AI lens of the newer Gauss design that I had factory converted to AI.

    The 10.5cm F2.5 black LTM Nikkor-P of mine has 10 aperture blades. It is a single coated lens.

    Another Nikkor for the F of mine is a 105mm F2.5 that is AI; it has 7 blades.

    And yet another 10.5cm F4 Nikkor-T is a THREE element preset lens for the Nikon F. It has NINE blades.
     
  9. Kelly,

    My mistake! I have the AIS Nikkor and it has seven blades. The opening is clearly a seven sided (not a hexagon) geometric shape at all but wide-open. The Elmarit M has a more round shape through out the aperture range. These shapes do show in the highlights. My points about the aperture shape and OOF renderings remain valid (from my experience).

    Sorry for my initial miss-count.
     
  10. Albert; thanks for the recount! <BR>Maybe you live in Florida or Alabama? :)
    <BR><BR>Ok bad joke!<BR><BR>I remember in the mid 1970's that some lenses were marketed with the added statement that an odd number of blades was better; one of the Nikkors I believe the 50mm F1.4 S to SC (multicoated) ...
     
  11. Thnx Kelly,

    I nearly smacked my 105mm Nikkor against the wall because i read an add back in the seventies which claimed 7 blades were better! *G*

    I am so amazed by your knowlege of camera lenses, your mother must soooo proud! ;)P

    (see.... bad jokes can be funny too!)

    Greetings,
     
  12. Kelly, you can still read the same thing in the 2000s:

    http://www.nikon.co.jp/main/eng/society/nikkor/n02_e.htm
     
  13. ...though it was the 50/2 Nikkor, not the f/1.4
     
  14. Kelly,

    Yes, I am from Florida, but in my defense, there was a hanging chad on one of my aperture blades. ;-)
     
  15. Kelly,I have a 105 10.5cm for the Nikon F that has 6 aperture blades. Very nice wide open. Also agree with Marc..I hate the OOF highlights with my Hassy lenses as well.
     

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