Hasselblad Zeiss lenses - number of aperture blades?

Discussion in 'Medium Format' started by christopher perez, Feb 23, 2006.

  1. How many blades are there in Hasselblad mount lenses? Does the number
    of blades vary between lens styles (ie: C, CF, CFi)?

    Last question: what is the shape of the aperture as it's stopped down?
    Truely round? Or some other multi-sided shape?

    OK, really Last Question: how does Rollei implement their aperture
    shapes in the 6000-series cameras?
     
  2. This kind of question, I leave it to David Odess. But does the shape of aperture, or the number of blades make a difference in how we capture an image?
     
  3. Five (5). I believe all lens series are the same in this respect. With 5 blades, the aperture is shaped like a pentagon. It is not round, except when fully open.

    Don't know much about Rollei 6000 but I assume they implement their aperture shape using blades.
     
  4. Christopher,<br><br>In shuttered lenses, the number of blades is 5, the shape therefor a pentagon.<br><br>The unshuttered lenses are different. The 80 mm has the same number of blades and shape. In the 50 mm, 110 mm and 150 mm lenses, the diaphragm is a bit more complicated (double), forming a near round shape at wider apertures, turning into the same pentagon at smaller apertures. The 250 mm lens has 8 blades and an octagonal aperture shape at all settings.
     
  5. "But does the shape of aperture, or the number of blades make a difference in how we capture an image?"

    Yes, the shape of flare artifacts take the shape of the aperture. Some folks like round flare more than they like hexagon- or pentagon-shaped flare.
     
  6. Paul,<br><br>The shape of the aperture determines the shape of difrraction patterns, and is most visible in unsharp parts, where the peculiarities/regularity of the shapes can cause visible patterns (like double contours).<br>Apart from that, bright, specular highlights often appear 'aperture-shaped'.<br><br>Aperture shapes are unavoidable, and, though perhaps the least disturbing when seen, a circle is a shape like any other.<br>Though pentagonal highlights might seem unnatural (and they are), round ones are that too (which is most obvious when produced by a mirror lens, when they have a dark bit in the middle).
     
  7. Chris - this is not a flame, but I'm surprised you ask this sort of question when you yourself have "tested" Hasselblad lenses at:
    http://www.hevanet.com/cperez/test/fourcameras.html
    and...
    http://www.hevanet.com/cperez/MF_testing.html
    ???? Odd.
    BTW, the Pentangular aperture hole on stopping down gives the 'Blad its characteristic "star highlights" for out-of-focus areas. Some people love this, others really hate it. Like Bokeh (which is weirdly smooth for the 'Blad, considering the 5-blade design), it's pretty much a question of personal taste.
     
  8. ...But does the shape of aperture, or the number of blades make a difference in how we capture an image?
    Yes. Significantly.
    I will be publishing an on-line article about the influence of aperture shape on out of focus areas shortly. My article will be related to large format lenses. After seeing what I've seen I was very curious about how apertures are implemented in medium format cameras. So I thought I'd begin with Hasselblad (and try and wriggle in a question about Rollei 6000-series).
    Thanks to everyone who responded with the answer.
     
  9. Chris - this is not a flame, but I'm surprised you ask this sort of question when you yourself have "tested" Hasselblad lenses...
    What I "tested" had to do with in-focus areas and had nothing to do with the influence of aperture shape on out of focus areas. At the time it didn't even occur to me to ask this kind of question. I made certain assumptions that had no relevence on the resolution of something, but more impact on the out of focus areas than I would have ever have guessed. :)
     
  10. All of the C, CF, CFE and CFi lenses has 5 aperture blades and thus they all makes pentagonal shape when stopped down. However. the apreture blades of C lenses are rounded and it is not until you stop down by one stop that the blades start to make a pentagon.

    I have bought a C Planar 80mm f2.8 for this particular reason. The shape of the pentagon is still very round even if you stop it down by 2 stops (at f5.6).

    Personally I cannot stand for the "true" pentagonal shape with perfectly straight sides that the aperture blades of CF and later models make.
     
  11. Hasselblad is the only manufacturer to offer you a choice of bokeh styles.
    Stop down and you get pentagonal highlights, shoot wide open and you get
    circular highlights. Damn clever these Swedes.
     
  12. Hasselblad is the only manufacturer to offer you a choice of bokeh styles. Stop down and you get pentagonal highlights, shoot wide open and you get circular highlights. Damn clever these Swedes.

    Actually, it is Carl Zeiss, and the sneaky Germans who manufactured the lenses for Hasselblad.

    Taras
     
  13. "Hasselblad is the only manufacturer to offer you a choice of bokeh styles. Stop down and you get pentagonal highlights, shoot wide open and you get circular highlights. Damn clever these Swedes."

    It's very clever to offer such feature from products made by Germans.
    They are even more clever to offer light meters from Skonics and Bossen.
    Don't forget they also offer you the best films from Kodak and Fuji.
     
  14. Another weird thing: I have an 80mm C T* lens that has 5 blades, but they are rounded at f/
    3.5, f/4 and f/4.5, and they start to get more pentagonal after f/5.6. I recently got a 80mm
    CFE, and the CFE has completely pentagonal blades at all apertures. I am kind of annoyed
    actually, as I am not a fan of the pentagonal highlights at all. Why change it? Luckily, my
    other lenses are the 50mm FE and 110mm FE, and they have rounded apertures when wide
    open.
     
  15. Akira -- I missed your post, but you and I have the same idea. I bought the 80 CFE to replace
    the 80 CT*, but now I don't know if I will get rid of it. Why would hasselblad do this? I know
    most other medium format lenses are like this, but if you look at Zeiss or Leica in 35mm,
    most of them have very round aperture blades...same with most Canon L lenses. It does not
    seem like it would cost all that much more to add a few blades. I have a Canon rangefinder
    lens with 10 blades that is completely round at every stop, why can't they just do that?
     
  16. OK, really Last Question: how does Rollei implement their aperture shapes in the 6000- series cameras?

    Five blades, a slightly rounded pentagram. That would explain the better bokeh. :)

    Ferdi.
     
  17. What is all this about round being better? The worst "Bokeh" in a Zeiss lens i have ever seen is produced by the f/2 110 mm lens, Wide open, so you can't get rounder.<br><br>By the way: why is it that the Hasselblad and Zeiss communities have managed for large parts of a century without having occassion to even mention Boke, while some other community (which will stay unnamed) seems to be obsessed by it?<br>Maybe it's not in the number and shape of the aperture blades... ;-)
     
  18. Hi, Stuart,

    Yes, I think we share the same idea. Hasselblad might have figured out that the pentagonal highlights appearing in the background could help them promote their products:)
     
  19. Maybe we should suggest to Hasselblad that they add two triangular notches to one of the aperture blades.
     
  20. I have to agree with Q.G. In my experience, except for the shape of the bright highlights due to back reflections, I find the number of blades to not be very important. Examples:

    I do not like the out of focus qualities of the Cf or Cfe 250, wide open. Round aperture. It's optics here that make me dislike it.

    I love the out of focus of the 120, wide open or not. So obviously it's optics here that make me like it.

    I think the OOF of 250SA is pleasing, again wide open or not, so again it's optics.

    It has appeared to me over an over again that the best indicator of the OOF smoothness is a fine tracking of the radial and tangential curves of the MTF at a given frequency. If you don't like MTF's (obviously there are a lot of vaiables, including the tester) then borrow, rent, or steal a lens and perform field tests. You'll see that the number of blades don't tell much.

    Again, this is ignoring the shape of reflections. Personally, I always use shades, try to keep bright light sources away from the very edge of the frame, use a secondary shade (piece of black cardboard, hand, anything to off-frame bright lights from striking the lens. Further, you would be amazed at the reduction of these back-reflections if you don't use a filter. When you have a large flat front element (filter) light reflecting out of the lens hits the flat surface and reflects back in again. I simply don't have much of a problem with these reflections.

    Some of these measures (large hoods, flags) are not practical in street photography, but them most folks are not buying MF slr's primarily for street work.
     
  21. Q.C. it is probably the different kind of publicum. From what I know, the Japanese are the ones that are more interested in the boken than anybody else. Would be interested to know how Hasselblad scores in that market... As for how much the five blades will influence the boken, here is my most extreme example. Taken with an extension ring + a 150mm CF lens: [​IMG]
    The pentagon is pesent everywhere and not only on the brightest highlights.
     

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