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#1 David Regan

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Posted 03 September 2007 - 07:52 PM

I've been attempting recently, to understand bokeh, such as what factors influence it, and how to spot it and understand it when I do see it. I recently saw a clip from Jackson's King Kong remake, and noticed something that confused me. In the first picture, I noticed the bokeh from the points of light in the background, to be fairly hard edged. However in the second picture the out of focus lights are very softly blended out. Now from what I had understood, the primary factor in the quality of a lens' bokeh, was the quality of the lens, and the hardness/softness depended on how much spherical abberation occured in the lens. So did perhaps they use different lens sets on this shoot, leading to different quailty bokehs, or are there other factors involved?

[attachment=2574:bokeh2.JPG]

[attachment=2575:bokeh1.JPG]
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#2 Chris Keth

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Posted 03 September 2007 - 08:25 PM

The bottom one looks like there's pretty heavy diffusion on the lens where the top one looks bare or nearly so.
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#3 Nick Mulder

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Posted 03 September 2007 - 09:26 PM

diffusion yes - but also the plain ol' fact that the bokeh in the first frame is probably from a source that much more resembles a real point source. i.e. pin prick of light and the second is an integration of many sharp edged 'bokehs' resulting from a larger source, like a practical light or something ...

The best way to understand it is to grab a zoom with a good telephoto end to it and go out at night and point it at different lights (distant, close and odd shaped) and pull both focus and zoom and watch the effect ... You'll see how hard it is to describe in words at the same time as going 'ahhh!' and understanding bokeh 10x the amount you would from watching films alone ...

Approaching car headlights are a goody - just dont walk into them... Very, 'Traffic' opening sequence ;)
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#4 Paul Bruening

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Posted 03 September 2007 - 09:46 PM

Everything changes bokeh. The same lens at different focus range can change the bokeh. The same lens at the same focus range but different aperture can change bokeh. The same frame composition and the same aperture, yet, different lens length can change the bokeh. Heck, I've got a Nikon 50mm, f1.4 and a Nikon 50mm, f1.2 and they have a different bokeh.

This accounts for one of the major reasons in cinematographer's obsession with bokeh. Ironically, there's more variety and creativity in the fuzzy parts than there are in the sharp parts of a picture. Wacky, huh?
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#5 Chris Keth

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Posted 03 September 2007 - 10:42 PM

One thing I forgot to mention before is that the bokeh of a particular lens is different on the far side of the plane of focus then it is on the close side. For example, uncorrected spherical abberation will cause the out of focus circles to be brighter on the edges when they are farther than the plane of focus. If they are closer, they will be brighter in the center and sort of fade out to the edges.

If the aperture is triangular, like in some super speeds, and the point of the triangle is up on the far side of the place of focus, then the point will be down in the bokeh for the foreground.
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