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Thread: Out of focus areas during lens movements

  1. #1

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    Out of focus areas during lens movements

    I have a two part question

    To start, a question of terminology. If a one uses lens movements (such as tilt) to achieve selective focus, is the quality of resulting out of focus areas still called bokeh?

    Is this bokeh in any way related to the regular bokeh (when the lens and the film are parallel to each other)? In other words, do lenses that are considered to have good regular bokeh also have good selective focus bokeh? How much of it is dependent on the degree of the movement (such as tilt)?

  2. #2

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    Re: Out of focus areas during lens movements

    Quote Originally Posted by arkady n. View Post
    I have a two part question

    To start, a question of terminology. If a one uses lens movements (such as tilt) to achieve selective focus, is the quality of resulting out of focus areas still called bokeh?

    Is this bokeh in any way related to the regular bokeh (when the lens and the film are parallel to each other)? In other words, do lenses that are considered to have good regular bokeh also have good selective focus bokeh? How much of it is dependent on the degree of the movement (such as tilt)?
    I don't know much about Bokeh because usually I'm concerned about what is in focus rather than what is out of focus. I understand that it can be a contentious issue. But one part of it is fairly straightforward. If the film plane is tilted with respect to the lens axis---which could happen either by tilting the lens or tilting the back---then the image of the aperture will be extended along an axis which will depend on just where in the field you are. The extension will be outward radially from where the lens axis hits the film plane, and the further away you are from that point, the great it will be.

  3. #3
    Abuser of God's Sunlight
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    Re: Out of focus areas during lens movements

    I've always been more concerned with the in-focus areas too, but the heated controversy over this is just baffling. You just have to look at fuzzy parts of pictures made by different lenses to see that they look different. And I agree with the bokeh fanatics that some kinds of fuzz are prettier than others.

    The quality of it changes not just from one lens to another, but from one aperture to another, and from one degree of de-focus to another. And it can be different for things in front of the plane of focus vs. things behind it.

    When you defocus something with movements, you're either putting it in front or behind the plane of focus. So it's really no different from defocussing in other ways. All the usual bokeh factors will apply.

  4. #4
    All metric sizes to 24x30 Ole Tjugen's Avatar
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    Re: Out of focus areas during lens movements

    Quote Originally Posted by arkady n. View Post
    Is this bokeh in any way related to the regular bokeh (when the lens and the film are parallel to each other)? In other words, do lenses that are considered to have good regular bokeh also have good selective focus bokeh? How much of it is dependent on the degree of the movement (such as tilt)?
    Yes, the bokeh is the same. but you will get both "front" and "back" bokeh, as the enclosed picture shows.

    So yes, lenses with "good bokeh" will still show "good bokeh", but the other side may well be awful!



    Schneider Xenar 300mm f:4.5 on FP4+ 5x7", full amd opposite front and back swing on a Linhof Technika 5x7" (and a smidgeon of front tilt).

  5. #5

    Re: Out of focus areas during lens movements

    Ole, that photograph has a truly weird plane of focus that just jumps out at you. Were you trying to get parts of both the railing and the cliff in focus or just demonstrating some whacky movements?

  6. #6
    All metric sizes to 24x30 Ole Tjugen's Avatar
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    Re: Out of focus areas during lens movements

    I was trying to get the railing and the building in focus, but overdid the rear swing. But on the whole I'm rather pleased with the result, and I don't think it would have been better if I'd got it "right".

  7. #7

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    Re: Out of focus areas during lens movements

    Quote Originally Posted by arkady n. View Post
    If a one uses lens movements (such as tilt) to achieve selective focus, is the quality of resulting out of focus areas still called bokeh?
    No, because the out of focus areas were never properly called bokeh. The blurred areas of the photos you take through a lens are called "out of focus areas." Bokeh is an intangible characteristic of a lens. The subjective appearance of the out of focus areas in a photo are affected by the bokeh of the lens.

    Quote Originally Posted by arkady n. View Post
    Is this bokeh in any way related to the regular bokeh (when the lens and the film are parallel to each other)? In other words, do lenses that are considered to have good regular bokeh also have good selective focus bokeh? How much of it is dependent on the degree of the movement (such as tilt)?


    As far as I can grok, movements don't have any appreciable effect on the lens' bokeh, other than the fact that some lenses can have different bokeh in the center vs the edges of the image circle. When you use movements on the front standard of a camera, it almost always results in the image being closer to one edge of the image circle. So I guess it's possible that a viewer might perceive the bokeh's effect differently, though I've never heard it mentioned.

  8. #8

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    Re: Out of focus areas during lens movements

    I've always understood that "bokeh" has to do with the optical quality of a lens and results from variations in the degree of optical correction achieved or failure to be achieved with that lens design. Other glass related issues can also contribute to "bokeh" such as type of glass, quality of surface, etc. I suppose an out of focus image can contribute to "bokeh" but it results from overlapping out of focus circles of confusion which IMHO impart a more mechanical aspect to the image.

    Nate Potter

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