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01-18-2008, 11:42 AM   #106
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QuoteOriginally posted by kenyee Quote
If that's true, they should attach another set of blades at an N degree offset to the regular blades. This would give you a better approximation of a circle which it seems is what they really want for better bokeh? I.e., the more blades/sides to the simulated circle, the better the bokeh?
This is one of the factors, yes. (And I would love for Pentax to come out with rounded aperture blades in the future.) But even if the aperture blades are perfect circles, they are still diffracting the light, and there are still inherent characteristics of the glass itself - hence the bokeh characteristics that apply both wide open and stopped down.

01-19-2008, 03:20 AM   #107
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Dueling Definitions

QuoteOriginally posted by mer Quote
hey jonas

interesting post . I am not really sure that bokeh = "quality of the out of focus parts of the picture", as in japanese bokeh , literally means "blur" / "fuzziness" .

Wikipedia says : Bokeh (from the Japanese boke ぼけ, "blur") is a photographic term referring to out-of-focus areas in an image produced by a camera lens. ...

From The Photographic Glossary: your Photo help page : Bokeh describes the rendition of out-of-focus points of light. Differing amounts of spherical aberration alter how lenses render out-of-focus ...
As I learned the term in the late '70s, and have often seen it used since, the definition given in The Photographic Dictionary best identifies the core of the Japanese concept. The rendition of out of focus points of light is what I always look at when someone discusses the bokeh in a photograph. It's what I always assume when someone says "lens X has nice bokeh." General OOF areas, whether foreground or background, are areas of falloff from the depth of focus in a particular image, usually described by the circle of confusion for a given point in the image exceeding some "acceptable" value. Hence, both types of description of OOF (points of light versus circles of confusion for a specified point) are a bit subjective (alright, downright fuzzy!) and really, if there is a meaningful difference in the concepts, I think the former involves description of a highlight point while the latter involves description of more middling toned areas.

Now, how about those angels on that pinhead over there?
01-19-2008, 06:45 AM   #108
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QuoteOriginally posted by d.bradley Quote
To throw something completely different into the bokeh mix, check out these examples:





Shot with the Minolta 35/1.4, you can see concentric circular texture in the specular highlights...never figured that one out...
Diffraction Rings. The offset nature of the diffractions rings in the image above seems to indicate a centering or collimation defect in that lens.

For further reading check out "Star Test" for astronomical lenses aka telescopes.
01-19-2008, 09:33 AM   #109
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QuoteOriginally posted by Rickster Quote
Diffraction Rings. The offset nature of the diffractions rings in the image above seems to indicate a centering or collimation defect in that lens.

For further reading check out "Star Test" for astronomical lenses aka telescopes.
Hey Rick,

I don't know about a defect. You could be right, but the concentric rings change placement depending on where the highlight is within the image frame...specular highlights on the right side of the frame are offset to the right, ones in the upper left offset to the upper left...

01-19-2008, 10:38 AM   #110
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QuoteOriginally posted by d.bradley Quote
Hey Rick,

I don't know about a defect. You could be right, but the concentric rings change placement depending on where the highlight is within the image frame...specular highlights on the right side of the frame are offset to the right, ones in the upper left offset to the upper left...
Yep, and orientation will switch 180 degrees if the 'star' object is in front of the focal plane vs behind.
01-20-2008, 09:56 AM   #111
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Hey Sean and Jonas,

The 85/1.8 SMC Tak was getting flak on another forum for rendering, but blades aside I think it does pretty well in a tough situation:

03-06-2008, 03:09 AM   #112
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A different kind of Bokeh:
An image consisting almost exclusively of Bokeh.
This is on the beach, setting the camera on the ground and shooting against the sun.

The reflecting grains of sand create a prism-like appearance.


Nokton, f4.0


Taken from my full test of the Voigtlander Nokton:
Voigtlnder Nokton 58/1.4 and Pentax 50mm lenses
03-06-2008, 03:18 AM   #113
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That is a very beautiful bokeh! Neutral but smooth creamy mixed with colours

03-06-2008, 10:23 AM   #114
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This has been a fascinating discussion. Thanks to all for sharing. I've enjoyed learning from your experiments.
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