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More Aperture Blades the better?
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PostPosted: Mon Apr 06, 2009 5:34 am    Post subject: More Aperture Blades the better? Reply with quote
It looks cooler to have more aperture blades in a lens, but does it make anything better in your pictures?


PostPosted: Mon Apr 06, 2009 6:11 am    Post subject: Reply with quote
I think more aperture blades create a more circular aperture. The more circular the opening, the more aesthetically pleasing the bokeh (OOF highlight rendition).

Oh, and it looks cooler Cool


PostPosted: Mon Apr 06, 2009 6:33 am    Post subject: Reply with quote
As Nelmu said, many blades (10 or more) make OOF highlights look circular.
This can make a difference in the bokeh especially at the middle apertures, where lenses with less blades look worse.

However, the more blades, the thinner they must be, and thus the easier to damage (and the harder to repair). Also, more blades mean the necessity of more grease to make the blades run smooth. This can (or can not) cause problems with the time, if grease is in excess. Excess grease is a typical problem of some soviet lenses with many blades.


PostPosted: Mon Apr 06, 2009 6:36 am    Post subject: Reply with quote
I noticed that the most recent production of the Mir-1 has 10 aperture blades - i'm not sure how many there are in the older versions. The optics are probably the same, so i guess only the bokeh effects change


PostPosted: Mon Apr 06, 2009 7:48 am    Post subject: Reply with quote
I think number of blades is the 3rd aspect, which has influence on bokeh. The 1st one is optical design. Some lenses has pleasant bokeh despite low number of iris blades. The second is shape of the blades. And than, number of them.

e.g. this picture was taken by Meogon enlarger lens. It has (only) 5 (but) rounded blades:

http://www.abload.de/img/sdim7763h4eje.jpg


PostPosted: Mon Apr 06, 2009 8:10 am    Post subject: Reply with quote
Excellent answers already!


PostPosted: Mon Apr 06, 2009 9:14 am    Post subject: Reply with quote
more aperture blades mean more circular OOF highlights
quality of bokeh have more to do with optical design
most of my lens have 6 blades but after 100000 digital shots, I never seen any hexagonal highlight
I believe some people compose expressly to get those highlights, like those who only shot walls
If you are a highlight fanatic, check this link for extra shapes
trimbone bokeh


PostPosted: Mon Apr 06, 2009 9:20 am    Post subject: Reply with quote
poilu wrote:

most of my lens have 6 blades but after 100000 digital shots, I never seen any hexagonal highlight
I believe some people compose expressly to get those highlights, like those who only shot walls


In 100000 digital shots you evidently never shot against some point lights.


PostPosted: Mon Apr 06, 2009 9:34 am    Post subject: Reply with quote
A G Photography wrote:
poilu wrote:

most of my lens have 6 blades but after 100000 digital shots, I never seen any hexagonal highlight
I believe some people compose expressly to get those highlights, like those who only shot walls


In 100000 digital shots you evidently never shot against some point lights.


many times! but usually it is night and then I shot only wide open Cool


PostPosted: Mon Apr 06, 2009 9:50 am    Post subject: Reply with quote
If you do a search for "aperture blades bokeh" you can find quite a few opinions, points of view, analyses & discussions. I have found the follwing two links to be helpful

http://rick_oleson.tripod.com/index-207.html

http://www.rickdenney.com/bokeh_test.htm


PostPosted: Mon Apr 06, 2009 10:50 am    Post subject: Reply with quote


link http://www.flickr.com/photos/mureena/154075085/


PostPosted: Mon Apr 06, 2009 11:28 am    Post subject: Reply with quote
This is very timely for me as I was pondering the same question while looking over the various lenses available to fill out my kit.


PostPosted: Mon Apr 06, 2009 2:57 pm    Post subject: Reply with quote
poilu wrote:
more aperture blades mean more circular OOF highlights
quality of bokeh have more to do with optical design
most of my lens have 6 blades but after 100000 digital shots, I never seen any hexagonal highlight
I believe some people compose expressly to get those highlights, like those who only shot walls
If you are a highlight fanatic, check this link for extra shapes
trimbone bokeh


I agree with this and No-X view. Current lens marketing would have us believe counting blades is a measure of bokeh quality - pure fantasy. As above - the only thing it influences is the shape of specular highlights when the lens is stopped down enough for the shape to be imparted. Further remember that the iris has no effect at all when the lens is wide open. Some (like myself) intentionally select a polygonal iris to acheive a specific look - forget the count as a measure of quality, only as a likely guide to the final shape.

A few samples:

Super Takumar - 6 blades (I think f2.8, note the hexagons are not rigid, as the iris was not fully shaped at this aperture)


Super Takumar - 6 blades


Trioplan wide open (blades have no effect, thus perfect circle)


Biotar 75 - wide open, perfect circles but note how the circles are not round as they approach the perimeter of the shot, optic formula has stretched even the perfect circles into 'cats eyes'.


PostPosted: Mon Apr 06, 2009 4:28 pm    Post subject: Reply with quote
Yep, the number of blades is quite irrelevant for a pleasant bokeh.

For instance, in the previous examples posted:

Hexagonal aperture, but uniform brightness and shape in out of focus areas = neutral, pleasant and beautiful bokeh
thePiRaTE!! wrote:



Perfectly round aperture, but not uniform brightness (see the bright rings around the oof lights) = unpleasant bokeh. When this happens, usually the situation is reversed at distances closer than the focus distance.
= unpleasant bokeh despite a perfectly round aperture
thePiRaTE!! wrote:


Worst case: brightness not uniform + lots of aberrations in out of focus areas = ugly bokeh, despite a circular iris.
thePiRaTE!! wrote:


The number of blades will also determine the star shape of strong lights when they're in focus (like the sun during the day).


PostPosted: Mon Apr 06, 2009 5:52 pm    Post subject: Reply with quote
Good or ugly bokeh is in the eye of the beholder...

/Jan


PostPosted: Tue Apr 07, 2009 11:24 am    Post subject: Reply with quote
poilu wrote:
A G Photography wrote:

In 100000 digital shots you evidently never shot against some point lights.


many times! but usually it is night and then I shot only wide open Cool


And thus, as the aperture blades were fully retracted, their number and shape had no effect on the image. Obviously.


PostPosted: Tue Apr 07, 2009 1:38 pm    Post subject: Reply with quote
nelmu wrote:
I think more aperture blades create a more circular aperture. The more circular the opening, the more aesthetically pleasing the bokeh (OOF highlight rendition).


Yes. One way to approximate a circle is to use a polygon with a greater number of sides. Another way is to not use straight lines to draw a circle in the first place. Curved blades is one way to do that. Not using a physical aperture at all, but defining a virtual one by a pair of (opposite direction) apertures equidistant around the optical crossing-point is another way(*).

The other thing that will affect the image, if there are very bright lights, are star-shaped rays. There will be twice as many rays as the number of blades. Their size seems (to me) to depend on the departure from circularity - a polygon gives more than a circle; a jagged polygon with little gaps gives worse ones, and an even-numbered polygon gives worse ones (because the rays reinforce) than a polygon formed by an odd number of blades.

* hand-wavy. There is doubtless a technical term for that place, which may be nodal point? but I don't know what the correct term is.


PostPosted: Tue Apr 07, 2009 2:49 pm    Post subject: Reply with quote
Wormhandler wrote:
Good or ugly bokeh is in the eye of the beholder...

/Jan

Spot on!

And it's probably only other photographers that notice it.


PostPosted: Wed Apr 08, 2009 2:15 pm    Post subject: Reply with quote
typically, I pick lens with more blades until I got Flektogon 35/2.4 which has six only. stunning bokeh


PostPosted: Wed Apr 08, 2009 2:40 pm    Post subject: Reply with quote
Shooting wide open at night is the proof that blades number is far from being everything for bokeh. Wide open, all apertures are circular just the same, but the highlights in bokeh are not the same! Some lenses will create perfectly smooth filled circles. Others will create doughnuts. Others will create doughnuts with a bright point in the middle. Other will show dirt or signs on the inside of the circle. Others will show aberrations affecting only one side of the circle, smudging it.
And all these things depend on the optical design and on the physical condition of the glasses, not at all on the number of the blades.
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