Aperture blade question


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stonko

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Aug 13, 2006
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#1
Hi guys, i have a used nikon 35-105mm F3.5-4.5 AIS manual nikkor. the other day i was looking through the lens to check for fungus and noticed that the aperture blades do not form a smooth opening from F3.5-F5.6. I mean, the blades should be forming a smooth shape and not have any jagged edges, right? is this normal?
 

Aug 12, 2006
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#2
you mean it's heptagonal instead of perfect circle?
 

stonko

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Aug 13, 2006
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#3
its not a perfect circle. i know most lenses dont have aperture blades that form perfect circles unless there are many blades. its something like a polygonal shape but at the vertices or edges, the blades are jagged as in the edges protrude out.
 

Snoweagle

Senior Member
Jan 26, 2005
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Pasir Ris, Singapore
#5
It all depends on the number of blade yr lens have. Usually to produce gd bokeh, should have at least 7 blades.
 

Artosoft

Senior Member
Aug 31, 2005
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Tanjong Katong
#6
Hi guys, i have a used nikon 35-105mm F3.5-4.5 AIS manual nikkor. the other day i was looking through the lens to check for fungus and noticed that the aperture blades do not form a smooth opening from F3.5-F5.6. I mean, the blades should be forming a smooth shape and not have any jagged edges, right? is this normal?
In which aperture do you see the jagged edges? If on max aperture, it should be ok. Closing down and you will see the jagged disappear.

Regards,
Arto.
 

Artosoft

Senior Member
Aug 31, 2005
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Tanjong Katong
#7
It all depends on the number of blade yr lens have. Usually to produce gd bokeh, should have at least 7 blades.
While it is true the number of blade usually can produce good bokeh, many factors in lens involved in produce good bokeh. For example: blade construction, glass quality, coating quality, max aperture, etc.

Regards,
Arto.
 

arpinkor

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May 13, 2005
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Nee Soon
#9
That "jagged edge" is ok because the the image "circle" at the focal plane is bigger than the sensor/film frame so the edge is not visible in your photos.
You'd need an infinite no. of blades to get a perfect circle anyway.
 

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