Uneven aperture blades?


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H4lcyon

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Jul 14, 2008
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Hi guys, I have a question regarding aperture blade opening of a lens. Does the blade opening have to be perfect and even on all side or can it be uneven like the pictures here?
(my 18-70 3.5-4.5)

Opening at smallest aperture. You can see the uneven sides.
DSC_0676.JPG


Mid-sized. One side is already a circle but the other side is still angular.
DSC_06851.JPG


Widest. It's a nice circle.
DSC_0687.JPG


I have another lens (50mm 1.8) and it looks perfect there. I'm just wondering whether I should bring it for service or just keep it for now, there's already some dust collecting inside it anyway. I don't think I see any effect on my pictures though.
 

I guess the blades might be a lil sticky there. Or that it is not able to match the others in the positions required.

You probably can inquire if someone can try to fix this for you at Nikon. Else you can check with Fatique if he can help you with this issue. ;)
 

I've seen two AFs 18-70 lenses, both have uneven aperture blades.
 

Aperture blades are like that. U won't get a perfect shape at smaller apertures, even for those with 'circular' blades.
 

:bsmilie: Thanks for clarifying. But why then do bokeh'ed regions look circular when the aperture blades form an opening that isn't circular? :dunno:
 

:bsmilie: Thanks for clarifying. But why then do bokeh'ed regions look circular when the aperture blades form an opening that isn't circular? :dunno:

Actually, they don't. You have a 50/1.8; stop it down to f/4 and shoot with highlights in the background, you will notice that they take on the shape of your aperture opening.
 

:bsmilie: Thanks for clarifying. But why then do bokeh'ed regions look circular when the aperture blades form an opening that isn't circular? :dunno:

coz the Bokeh'ed regions are normally from wide open lenses.. and they are generally round at that stage. ;)
 

oooooooo
i've never really noticed the aperture blades are liddat:embrass:
 

Aperture blades are like that. U won't get a perfect shape at smaller apertures, even for those with 'circular' blades.

Depends on the lens too. Most of my lenses maintain a circular shape till about f/5.6, but after that the aperture blades remain in a fairly symmetrical shape
 

Aperture blades are like that. U won't get a perfect shape at smaller apertures, even for those with 'circular' blades.

Depends on the lens too. Most of my lenses maintain a circular shape till about f/5.6, but after that the aperture blades remain in a fairly symmetrical shape

Same here too...the five-bladed aperture on my 35mm f/2 is a symmetrical pentagon when stopped down.

Snoweagle, do you have any additional info that backs up your statement?
 

Actually, they don't. You have a 50/1.8; stop it down to f/4 and shoot with highlights in the background, you will notice that they take on the shape of your aperture opening.

coz the Bokeh'ed regions are normally from wide open lenses.. and they are generally round at that stage. ;)


ahh, i see.Thanks a lot! :sweatsm:

didn't exactly measure the dimensions of OOF points of light in my photos :bsmilie:
 

ahh, i see.Thanks a lot! :sweatsm:

didn't exactly measure the dimensions of OOF points of light in my photos :bsmilie:

Haha no its not the dimensions; it's the shape. With a five-bladed pentagonal aperture, you will get pentagonal highlights when you stop down.
 

hmm...after reading snoweagle's post i tried on my two lens and both got even aperture blades leh...

i'm also pondering.. for extreme case if one of the several blades doesn't close at all, would it affect the DOF of the image since more lights went thru and also the exposure etc?
 

yea...the dimensions of the shape? :bsmilie:

The dimension do not matter as they are made from the light source. The larger the source, the larger the shape.

It's the shape of the it tat matters... the rounder, the better the aperture blades are able to make a circle. And normally you'd see it clearly when shooting wide open. This is when the blades are fully RETRACTED, you dun even see them...
 

I have seen more than 20 of this lens.
Most of them got uneven aperture blades

There's no problem with your lens

Problem with the construction? Or design issue?
 

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