NikonGear'23
Gear Talk => Lens Talk => Topic started by: oldfauser on March 04, 2016, 01:57:53
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I was looking over my collection of Nikkors, and noticed that they all have 7 aperture blades - not one has 9 (or 6)!
am i missing something? Or is this something not to worry about... Should i look at getting a 9 blade lens in the future?
Thoughts?
Art
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Depends on your shooting style.
If you shoot these lenses closed down with boke balls in the background you will see less round circles, wide open it doesn't make a difference as with most lenses the inner barrel determines the wide-open aperture characteristics and not the aperture blades themselves.
Personally I use my lenses wide open most of the time so don't care about the amount of aperture blades, other character aspects are way more interesting IMHO :)
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Early Nikkors had 7 and with time 9 became more common.
The more the number of blades, the more circular opening as the aperture closed down. In the '50s, lenses having a large number of blades were frequent. However, there are drawbacks as more blades meant a more complex mechanism. This is important as the aperture operation became linearised with the arrival of TTL metering towards the end of the '70s and this in conjunction with motor drives and demands for faster operation spoke against the high-numbered aperture design. Modern optical designs try to balance the shape of the aperture opening against other desirable optical qualities. Thus, more blades usually confer a smoother out-of-focus rendition.
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The number of blades also determines the number of rays rendered on point light sources (sun/starbursts) as well as the shape of the rays. Odd numbers double the points,so 8 blades makes 8 rays while 9 blades makes 18. Curved blades cause the rays to fan out as the grow longer, while straight blades cause more focused rays that narrow to points. Ai-s lenses are more commonly found with 9 blades on the faster versions of a given focal length.
Roland's page is extremely handy for these details.
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The [edge of each blade causes] diffraction with one spike going outwards and the other inwards. With an odd number of blades the spikes don't over lap so you get two times the number of spokes with half being slightly stronger than the other half. [With an even number of blades, opposite blades reinforce each other's spokes for fewer, stronger spokes.] I prefer a nine blade aperture that is quite round at larger apertures becoming more of a polygon at smaller apertures.
There are other image consideration than diffraction stars and point light orbs. I'll have to poke the web to refresh my memory or I'll shortly have my foot deep inside my mouth.
Dave
Edited per Roland's post below.
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The intersection of two blades cause a diffraction spoke ...
NO, it's the edge of the aperture opening which causes diffraction. Diffraction is an edge effect - light passing near the edge bends a bit. If the edge is straight the light all bends in the same direction so you get a directional diffraction spike on your image. Lenses with rounded aperture blades cause the diffraction to spread out evenly in all directions which causes a diffuse halo around point sources of light instead of a diffraction star.
Also, because diffraction is an edge effect, it becomes greater at small apertures since the edge / area ratio increases.
To the original question, there is nothing wrong having all lenses with 7 aperture blades. I think it is a good feature. Lenses with 6 or 8 aperture blades produce less interesting defocus blurs - the shapes are too regular and "square". Having an odd number if sides looks more natural and organic to me.
The very first F-mount Nikkors had 9 aperture blades, but they soon reduced to 6. The earlier rangefinder lenses had as many as 16 aperture blades. Rangefinder lenses are always stopped down to the shooting aperture, they don't move when the picture is taken so the aperture mechanism can afford to be heavy and well-built. However SLR lenses must have an aperture which opens and closes very quickly - wide open for TTL viewing and then stopping down instantly at the moment of exposure. Therefore the aperture blades must be very lightweight so they can move quickly. Maybe the early 9-blade apertures were too heavy with too much friction to operate quickly, or they were too complex and expensive. During the 1960s and 70s the number of blades changed to 7, possibly because it is a nicer shape. Lenses with very fast aperture, and telephotos had 9 aperture blades to give the opening a rounder shape, since the shape of the aperture is more noticeable in pictures taken with these lenses.
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An oddity for the f-mount :o :o :o
Odd numbers feel more organic. i am yet to meet a person who prefers 6 bladed irises.
by the way, if i am not mistaken, the 28mm f/3.5 only has 5 aperture blades. i have cleaned 2 so far and i remember that they only had 5...i can check later
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Ohhhhh. They sold me a rubbish lens with too many blades........
(http://img.photobucket.com/albums/v233/Duke_1/_MG_3285_zpsnxcjqku1.jpg)
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Roland,
Thanks for the correction. It's obvious now that I've thought it out. :-[
Best,
Dave
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Ohhhhh. They sold me a rubbish lens with too many blades........
I have Russian lenses from the '50s with up to 21 blades ....
By the way, the optics indeed were rubbish, but I doubt the aperture was the main reason.
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I have enlarger lenses with 3 aperture blades. A Schneider-Kreuznach cine lens (used by me for photomacrography) have 4 giving peculiar highlights ... Early Hasselblad lenses had 5, and the Nikkor-S 35 mm f/2.8 had 6.
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number and shape
(https://c1.staticflickr.com/9/8625/16430307796_70589103c5_z.jpg)
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Arend, wow. That is strange looking! What kind of rays does that produce? I can imagine the strange bokeh.
I hope we see a retur n in using straight blades someday. I'd rather have a higher number of straight blades personally, though I know I am a minority
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Schneider-Kreuznach made a lot of enlarging lenses in the 1970's(and maybe later) with the 'reversed curve' blades. I cannot imagine that it helped the imaging performance of the lens, but maybe it didn't hurt?
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by the way, if i am not mistaken, the 28mm f/3.5 only has 5 aperture blades. i have cleaned 2 so far and i remember that they only had 5...i can check later
My Type K version appears to have 7.
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One would think as close to round would be the best, but I don't think about stuff like this much.
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My Type K version appears to have 7.
So does my K and AI of the 28/3.5. There is an H earlier model somewhere but cannot find it at present. Might even be in another lens house.
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One would think as close to round would be the best, but I don't think about stuff like this much.
The basic requirement is about the area of the opening, not abound its circularity. Fewer blades make for a snappier operation.
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One would think as close to round would be the best, but I don't think about stuff like this much.
For oof rendition the vast majority would agree, as do I. For rays, I strongly prefer straight blades. It is an issue of compromise, though it is a very easy one for most. I don't see straight blades making a return unless someone decides to stand out by making something with 13+ straight blades.
The Jupiter 3+ 50mm f/1.5 has 13 curved blades, so there are aome niche products out there with high blade count. The Song G series have 11 curved blades. Perhals when the sharpness trend has faded, we will see fompanies trying to stand out with different blade setups.
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So does my K and AI of the 28/3.5. There is an H earlier model somewhere but cannot find it at present. Might even be in another lens house.
I've got an early version Nikkor-H with the small rear element, it does in fact only have 5 blades.
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The basic requirement is about the area of the opening, not abound its circularity. Fewer blades make for a snappier operation.
Circularity ensures the minimum edge length for a given area (f/stop), so diffraction is also minimized.
I've got an early version Nikkor-H with the small rear element, it does in fact only have 5 blades.
This is the only F-mount SLR lens with 5 aperture blades. I guess due to the wide angle of view and large DOF, Nikon decided they could get away with fewer blades since bokeh is not much of a concern with this lens. Most other Nikkors from the same period had 6 or 7 aperture blades.
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number and shape
(https://c1.staticflickr.com/9/8625/16430307796_70589103c5_z.jpg)
My Nikkor-T 10.5cm 1:4 lens has an opening like that around f/5.6-8, but only 9 aperture blades. If there are specular highlights in the background (or foreground), such as light reflecting off foliage, it can produce interesting star shape blurs!
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A circular aperture will produce the biggest shift in focus due to spherical aberration. Lenses with shaped apertures offset the shift. Spherical aberration basically means the focal length of the lens is not constant as you go from the center of the lens to the edge of the lens. The West-German 50/1.5 Sonnar and the current C-Sonnar both have shaped apertures, most other Sonnars have circular apertures.
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leica 21mm f4 super angulon has 4 aperture blades,,, :o
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A circular aperture will produce the biggest shift in focus due to spherical aberration. Lenses with shaped apertures offset the shift. Spherical aberration basically means the focal length of the lens is not constant as you go from the center of the lens to the edge of the lens. The West-German 50/1.5 Sonnar and the current C-Sonnar both have shaped apertures, most other Sonnars have circular apertures.
So that is why so many of the Leica M lenses has these strangely shaped blades I presume,,, since focus shift is a killer for Leica M mechanical rangefinders.
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The first generation Zeiss high speed primes for cinematography had three-sided irises, achieved using nine blades(!)...maybe they were concerned with focus shift?
To see the 3 bladed irises, scroll down at the linked site:
http://cinematechnic.com/resources/zeiss_super_speed_f12_lenses (http://cinematechnic.com/resources/zeiss_super_speed_f12_lenses)
Many Super-8 film cameras in the 1970's featuring auto exposure had two-bladed irises, yeilding a diamond shaped OOF highlight.
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Six Blades. I think i like the Micro Nikkor 55mm 3.5.... :D
(https://farm2.staticflickr.com/1521/24649917513_f932adb6e0_h.jpg) (https://flic.kr/p/DyegFP)
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Great shot Harald.
Six Blades also with the Nikkor K 85/1.8 Must be the reason I adore this lens ;)
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Do not show this photos in any other forum! ;D
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I'm not sure if it is considered "First Generation"- but this 1927 Carl Zeiss Jena 4cm F1.4 uses lots of blades for a circular aperture. I think it is "Debrie" mount, under 300 made. I found of described in a Zeiss catalog of the era as "Objective of Extreme Rapidity", meaning "fast". Marketing from 90 years ago.
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A circular aperture will produce the biggest shift in focus due to spherical aberration. Lenses with shaped apertures offset the shift. Spherical aberration basically means the focal length of the lens is not constant as you go from the center of the lens to the edge of the lens.
I don't understand how this ... Yes spherical aberration means the focal length is not constant as you move from the center to the edge of the lens. For a given aperture, a circular opening will have a minimum overall radius, which surely will minimize the focal length shift from center to edge. A "shaped" aperture will need to have parts of the opening further distance from the center which would tend to increase focus shift. Or am I missing something?
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The circular aperture eliminates light from the edges, produces the most dramatic shift.
A shaped aperture accepts light from closer to the center and closer to the edges, mixes light from the different focal-length regions, hence spreads out the DOF.
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The most dreadful aperture I've ever seen was that of the licensed Planar 85/1.4 for Rollei SL2000F/3003. There are only three blades which made an exemplary Riemannian triangle.
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Schneider - Kreuznach Tele-Zenar 150mm f5.5
Mongo bought this old Schneider for next to nothing over 30 years ago. Put a "T" mount on it and discovered it was wonderful to use for portrait photos (and probably little else). Very low contrast with a soft mellow feel which lends itself to portrait work. No less than 18 nicely rounded aperture blades constructed with beautiful precision and movement. Small - about 80mm long and 50mm at its widest. it is quite light but has a very solid feel. Focus wide open and then manually stop down before pressing the shutter button. Bit fiddly but not so much a problem for slow or studio portrait work.
There is little doubt the number and design of the aperture blades give this lens its distinct character.
Are there any advance bids on 18 blades...? ;D
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Old list from another forum:
Schneider Xenar 3.5/240: 30 blades
Noflexar 5.6/400mm: 24 blades
TAIR-11A 2.8/135mm: 20 blades
Komura Koki Tokyo 2.8/135mm: 20 blades
Meyer-Optik G�rlitz Orestegor 4/300mm: 19 blades
CZJ Biotar T 5.8/2, 58/2 (manual): 17 blades
TAIR-3S 4.5/300mm: 16 blades
Steinheil M�nchen Culminar 135 & 85mm: 16 blades
Sankyo Kohki Komura 105mm f/2.5: 16 blades
Isco-G�ttingen Tele-Westanar 135mm f/3.5: 15 blades
Ernst Leitz Wetzlar Summarit: 1.5/5cm: 15 blades
Ernst Leitz Wetzlar Hektor 13,5/4,5: 15 blades
Vivitar 85/1.8 (T-mount): 15 blades
Jupiter-9: 15 blades
Meyer Trioplan V 100/2.8: 15 blades
Meyer Orestor (preset Pentacon) 135/2.8: 15 blades
Meyer Telemegor V 180/5.5: 15 blades
Meyer Orestegor 200/4: 15 blades
Meyer Primoplan V 75/1.9: 15 blades
Meyer Primoplan V 58/1.9 (manual, pre-set): 14 blades
CZJ Flektogon T 35/2.8 (pre-set): 14 blades
KMZ Helios 44 58/2 (old KMZ version): 13 blades
ZOMZ Jupiter-3 Π 50/1,5: 13 blades
Meyer Telefogar V 90/3.5: 12 blades
Meyer Trioplan 50/2.8: 12 blades
CZJ Biotar T 58/2 (early pre-set model): 12 blades
CZJ Biometar 80/2.8 (pre-set): 12 blades
CZJ Tessar T 40/4.5 (manual): 10 blades
CZJ Biotar T 75/1.5 (pre-set): 10 blades (round at f/1.8 and f/16)
Meyer Helioplan V 40/4.5 (pre-set): 10 blades
Meyer Primagon V 35/4.5 (pre-set): 10 blades
Asahi Auto Takumar 35/2.3: 10 blades
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Old list from another forum:
Schneider Xenar 3.5/240: 30 blades
Noflexar 5.6/400mm: 24 blades
TAIR-11A 2.8/135mm: 20 blades
Komura Koki Tokyo 2.8/135mm: 20 blades
Meyer-Optik G�rlitz Orestegor 4/300mm: 19 blades
CZJ Biotar T 5.8/2, 58/2 (manual): 17 blades
TAIR-3S 4.5/300mm: 16 blades
Steinheil M�nchen Culminar 135 & 85mm: 16 blades
Sankyo Kohki Komura 105mm f/2.5: 16 blades
Isco-G�ttingen Tele-Westanar 135mm f/3.5: 15 blades
Ernst Leitz Wetzlar Summarit: 1.5/5cm: 15 blades
Ernst Leitz Wetzlar Hektor 13,5/4,5: 15 blades
Vivitar 85/1.8 (T-mount): 15 blades
Jupiter-9: 15 blades
Meyer Trioplan V 100/2.8: 15 blades
Meyer Orestor (preset Pentacon) 135/2.8: 15 blades
Meyer Telemegor V 180/5.5: 15 blades
Meyer Orestegor 200/4: 15 blades
Meyer Primoplan V 75/1.9: 15 blades
Meyer Primoplan V 58/1.9 (manual, pre-set): 14 blades
CZJ Flektogon T 35/2.8 (pre-set): 14 blades
KMZ Helios 44 58/2 (old KMZ version): 13 blades
ZOMZ Jupiter-3 Π 50/1,5: 13 blades
Meyer Telefogar V 90/3.5: 12 blades
Meyer Trioplan 50/2.8: 12 blades
CZJ Biotar T 58/2 (early pre-set model): 12 blades
CZJ Biometar 80/2.8 (pre-set): 12 blades
CZJ Tessar T 40/4.5 (manual): 10 blades
CZJ Biotar T 75/1.5 (pre-set): 10 blades (round at f/1.8 and f/16)
Meyer Helioplan V 40/4.5 (pre-set): 10 blades
Meyer Primagon V 35/4.5 (pre-set): 10 blades
Asahi Auto Takumar 35/2.3: 10 blades
Ohhhh, blast, I only have 3 lenses of this list 8)
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oh double blast !......that is a lot more than 18 blades !
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Wow, I wonder how they can count the blades correctly in the first place. I always lose where I start counting. :o :o :o
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The circular aperture eliminates light from the edges, produces the most dramatic shift.
A shaped aperture accepts light from closer to the center and closer to the edges, mixes light from the different focal-length regions, hence spreads out the DOF.
OK, but a shaped aperture would have to be extremely "out of round" to have a noticeable effect. In most non-circular apertures, the portion of light transmitted through the irregular outer area is very small in comparison to the central part - even the triangular aperture mentioned earlier - so mixing of light from different-focal-length-edges regions is hardly greater than a circular aperture. Also, most non-circular apertures close down from all directions - light is eliminated from the edges - when stopped down so you are still going to get focus shift. I'd say on most commonly used lenses, the shape of the aperture has a negligible effect on focus shift.
If you are really going to minimize focus shift on stopping down you need an aperture which continues to transmit light across the entire radius on stopping down. For example a cat's eye which is near circular (wide open) for night vision but closes down to a slit in bright light. Such an aperture would produce unusual DOF effects, since the DOF in the vertical direction hardly changes on stopping down, but increases greatly horizontally (hmmm... could be interesting).
Another example are the "sink strainer" stoppers used with some large format cameras. In some ways these act a bit like a neutral density filter in that they reduce the amount of light passing but still transmit across much of the aperture radius, so the DOF is not altered greatly.
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Wow, I wonder how they can count the blades correctly in the first place. I always loose where I start counting. :o :o :o
Akira, you are so right ;D
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Akira, you are so right ;D
:'( :'( :'(
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The West German Carl Zeiss 50/1.5 Sonnar (also under Opton name) and the modern C-Sonnar use a shaped aperture that staggers effects of spherical aberration from ~F2.8 to ~F5.6. This is where the focus shift is greatest on the Sonnar.
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Wow, I wonder how they can count the blades correctly in the first place. I always lose where I start counting. :o :o :o
It's easy, while looking into the front of the lens, use a metal tool to make a scratch on the front element over the first blade you count. That way you can't forget where you started! ;)
Jokes aside, while I love high numbers of rays, 18 is already quite high and I think much higher might make them look too cluttered. Perhaps 9 is a good balance.
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Working on a Leica lens, take off the front section and turn the lens upside down.
You will have an easy time counting them after they fall out. I've only had that happen once.