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Min Lee · October 2nd, 2006, 06:52 PM

Does the number of shutter blades affect anything else besides the shape of the bokeh?

Frank Hool · October 2nd, 2006, 10:46 PM

Rather actual shape of open iris. But yes.

Min Lee · October 3rd, 2006, 04:10 PM

Care to elaborate? What are the advantages or disadvantages to more or less blades?

In other words, I like the pentagon shape I get from the 5 blades on my canon FD 50mm 1.8, but am I sacraficing anything else like light fall off, sharpness, etc. I also have a 55mm 1.2 which has 8 blades I think. I don't notice any difference besides light loss but I don't have trained eyes.

Frank Hool · October 4th, 2006, 11:13 AM

http://en.wikipedia.org/wiki/Diaphragm_(optics)

Quote:

The number of blades in an iris diaphragm has a direct relation with the appearance of the blurred out-of-focus areas in an image, also called Bokeh. The more blades a diaphragm has, the rounder and less polygon-shaped the opening will be. This results in softer and more gradually blurred out-of-focus areas.

just one more elaboration to this: All iris diafragms are designed to be virtually rounded in one posistion(in open). In other positions are corners between lamellas better seen.

Dennis Wood · October 4th, 2006, 11:43 AM

Perhaps the biggest difference is bokeh quality in out of focus specular highlights. Some have suggested that hexagons are more distracting (and I would agree), than the rounder shapes produced by cinema type lenses. Given that edge diffraction from the blades should not be an issue below f16, I suspect the largest difference is just the bokeh thing for adapter purposes.

Ben Winter · October 4th, 2006, 05:12 PM

Quote:

Originally Posted by Dennis Wood

than the rounder shapes produced by cinema type lenses

Actually cinema lenses produce quite polygonal specular highlights. One notable example is the shot of Denzel Washington in the car talking with Jodie Foster, in the movie "Inside Man." Specular highlights are clearly visible through the windshield of the car, and they're quite polygonal, in fact more so than what I've achieved with my Canon FD's.

October 2nd, 2006, 06:52 PM	#1
Min Lee Major Player Join Date: Sep 2005 Location: San Francisco, CA Posts: 200	shutter blades Does the number of shutter blades affect anything else besides the shape of the bokeh?

October 2nd, 2006, 10:46 PM	#2
Frank Hool Major Player Join Date: Apr 2006 Location: Barca Spain Posts: 384	Rather actual shape of open iris. But yes.

October 3rd, 2006, 04:10 PM	#3
Min Lee Major Player Join Date: Sep 2005 Location: San Francisco, CA Posts: 200	Care to elaborate? What are the advantages or disadvantages to more or less blades? In other words, I like the pentagon shape I get from the 5 blades on my canon FD 50mm 1.8, but am I sacraficing anything else like light fall off, sharpness, etc. I also have a 55mm 1.2 which has 8 blades I think. I don't notice any difference besides light loss but I don't have trained eyes.

October 4th, 2006, 11:43 AM	#5
Dennis Wood Major Player Join Date: Mar 2005 Location: Ontario, Canada Posts: 916	Perhaps the biggest difference is bokeh quality in out of focus specular highlights. Some have suggested that hexagons are more distracting (and I would agree), than the rounder shapes produced by cinema type lenses. Given that edge diffraction from the blades should not be an issue below f16, I suspect the largest difference is just the bokeh thing for adapter purposes.