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01-15-2013, 05:41 AM   #31
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QuoteOriginally posted by Anvh Quote
as long as there aren't any highlights to give away the shape of the aperture you won't spot it.
That's exactly when it becomes useful.

It seems to me you are saying "in situations where there is no usefulness for round apertures, you can't spot their presence"

01-15-2013, 07:32 AM   #32
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Yep preciesly but some are promoting it as the way to smoother bokeh but that isn't true.
That's where my problem lies.

And like i said before the shape of the highlights is not bokeh, they are two different things.
01-15-2013, 11:09 AM   #33
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QuoteOriginally posted by Anvh Quote
Yep preciesly but some are promoting it as the way to smoother bokeh but that isn't true.
That's where my problem lies.

And like i said before the shape of the highlights is not bokeh, they are two different things.
Agreed. I think it could still benefit some lenses. Macro lenses are already designed to offer great bokeh, so round apertures, while useful on paper, might not be that noticeable. But on the other hand, take the Da21 (whose bokeh I find very interesting, but far from smooth) and add round blades, you WILL see a difference. You will also loose its capability to create beautiful stars around light sources...
01-15-2013, 11:19 AM   #34
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QuoteOriginally posted by bdery Quote
But on the other hand, take the Da21 (whose bokeh I find very interesting, but far from smooth) and add round blades, you WILL see a difference.
Nope since the shape of the "blur disks" is not bokeh.

This site was recommended by the person who introduced the word bokeh in ther western world.
Bokeh

QuoteQuote:
Characterization of the blur disk

Since any image is represented by a large number of images of points, we may attempt to understand the whole by considering the blurring of a single point. An unsharply imaged point is associated with a circle of confusion, or a blur disk. This blur disk is characterized by
  1. A size.
  2. A shape.
  3. The light distribution across the disk.

The size of the disk determines the "amount of blur". The shape of the blur patch does not need to be circular, in which case the designations "circle of confusion" or "blur disk" are misnomers. Nonetheless, for convenience the word disk will be freely used to mean a patch of arbitrary shape. Although the size and the shape of the disk are unmistakable blur characteristics, they do not touch the essence of bokeh as the Japanese intended the word. The distribution of light across the disk does [1]. However, the distinction is not always clear and what follows is intended as an overview of a variety of factors that influence the rendering of OOF image parts. Explanations of the underlying mechanisms will be brief and the reader is referred to other pages for elaborateness.


01-15-2013, 11:56 AM - 2 Likes   #35
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I think this would be a perfect time to cement my place in photographic history.

I hereby dub the out of focus blur disks... Tarbs.

As in "These Ain't Really Bokeh".

I won't even ask royalties for the use of the word!
01-15-2013, 04:45 PM   #36
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QuoteQuote:
Although the size and the shape of the disk are unmistakable blur characteristics, they do not touch the essence of bokeh as the Japanese intended the word. The distribution of light across the disk does [1].
The size and shape of the disk does not affect the light distribution across the disk? That doesn't make any sense. If you shrink the disk, surely, the light distribution in the area that is now outside has changed. A lot!
01-15-2013, 05:02 PM   #37
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You shrink the disk but the distribution inside the disk stays the same, therefore the bokeh stays the same.

Not sure what you mean with "outside"
01-15-2013, 07:22 PM   #38
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Anvh, I think you are wrong that the shape of the highlights is not part of what is included in the term "bokeh." Whatever bokeh used to mean, to most people, it means generally the rendering of out of focus areas of an image. Wikipedia says: Bokeh has been defined as "the way the lens renders out-of-focus points of light". If an image has no points of light, rounded aperture blades will not make a difference one way or the other on the image. If there are points of light, a rounded aperture can give a much more pleasing image.

http://en.wikipedia.org/wiki/Bokeh

01-15-2013, 07:29 PM   #39
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QuoteOriginally posted by Anvh Quote
You shrink the disk but the distribution inside the disk stays the same, therefore the bokeh stays the same.
Shrinking the disk while the light distribution inside stays the same, is equivalent to keeping the disk the same and lowering the light intensity in an outside ring. Since any size change can be mapped onto an intensity change without changing size and shape, it does not make sense to postulate that Bokeh is affected by one and not the other.
01-15-2013, 11:47 PM   #40
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QuoteOriginally posted by bdery Quote
Macro lenses are already designed to offer great bokeh
Well, I be...you learn something new every day.


Steve
01-16-2013, 01:01 AM   #41
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Read the white paper from Zeiss on Depth of Field and Bokeh:
We therefore want to deal with blurring in the following pages. This image attribute is indeed more of an aesthetic and therefore subjective nature and cannot be described as simply with figures as it is the case with a well focused, sharp image. Thus its subtleties in lens tests play no important part sometimes. This is quite different in Japan: as well as figures for contrast, resolution etc., every test always includes examples of images with blurred flowers, leaves and other items which often act as the background to photographs. It is therefore perfectly right that the Japanese word “bokeh“ is used around the world as a collective term for all attributes of blurring.

The root of the Japanese word boke or bokeh* actual means nothing good; its meaning is similar to “confused” or “dizzy” and is used to name mental states in exactly the same way. In photography the term ”confused“ relates naturally to light beams which no longer come together at a single point in an orderly manner.

In spite of the subjective nature of the matter we nevertheless want to attempt to remain faithful to the style and character of our technical articles by describing bokeh with some numbers. Of course, this cannot be done on very simple scales, for example, “a grade 5.5 bokeh“, because blurring always depends on a large number of parameters. But figures can help us to improve our understanding of connections.

All the parameters listed here influence the phenomena outside the focal plane:
• Picture format
• Focal length
• f-number
• The camera-to-subject distance
• Distance to the background or the foreground
• Shapes and patterns of the subject
• Aperture iris shape
• Aberrations of the lens
• Speed of the lens
• Foreground/background brightness
• Colour
It is therefore not surprising that one often hears different and sometimes contradictory judgements about the bokeh of many lenses. Undue generalisations are all too often drawn from single observations.
Many effects are attributed to the lens even though they are mainly caused by the subject in front of the camera. Differences between lenses are often very marginal but are then grossly exaggerated.
There is a whole section on the Aperture Iris Image. The author states this:
The aperture of the lens determines the basic area of the light cones which do not appear exactly as the cones in our school books. We therefore see the number and shape of the iris blades if the sensor plane intersects with the cone at a position where is cross-section area is still very large.

Such iris images can be very decorative items in a picture. If they are strikingly bright they attract the view of the observer. A ‘beautiful’ geometry of the iris is therefore desirable. But an iris image reminiscent of a saw blade as in the example below on the left is often perceived as disruptive.

With a sufficiently large number of iris blades and a suitable curvature it is possible to come close to the ideal of a circular aperture. Regular pentagons or hexagons which were frequently seen in earlier days are now felt to be too ‘technical’. But at the end of the day it is naturally a matter of taste.

So it would seem the engineers at Zeiss consider aperture iris image to be a consideration of "bokeh".
01-16-2013, 07:22 AM   #42
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QuoteOriginally posted by Ikarus Quote
Shrinking the disk while the light distribution inside stays the same, is equivalent to keeping the disk the same and lowering the light intensity in an outside ring. Since any size change can be mapped onto an intensity change without changing size and shape, it does not make sense to postulate that Bokeh is affected by one and not the other.
Nope that isn't the case or else your blurred background will be much darker then the parts that are sharp and that isn't the case right.
01-16-2013, 07:35 AM   #43
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QuoteOriginally posted by Not a Number Quote
So it would seem the engineers at Zeiss consider aperture iris image to be a consideration of "bokeh".
Mhmm 3 aperture blades or 4 doesn't work well but above 5 you will not be able to see a differnce.
Beside that i'm looking at the source and you... Zeiss did not come or invetned this term so do they really know what it is about?
01-16-2013, 12:16 PM   #44
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QuoteOriginally posted by Anvh Quote
Nope that isn't the case or else your blurred background will be much darker then the parts that are sharp and that isn't the case right.
I'm not sure what you're getting at with this. The narrowing of the highlight would correspond to a closing down of the aperture, so both will get darker.

Anyway, it's really quite straight forward. Whatever it is that shows up in the out-of-focus background for an isolated point light source is the blurring function applied to the out-of-focus areas at that position in space, so the final image is affected by all of its properties, including size and shape. Do these properties always matter in the same way? Of course not. It depends on the background properties. At the other extreme of the single light source there is a flat, even-colored wall, where none of this matters.
01-16-2013, 01:32 PM   #45
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Was talking about the about the relatieve size, half of 1km is of course less then the half of 1m but you're right they are both halves so the balance in light is still there, forgot about that so that statement was wrong of mine.

Yep you say it correctly, out-of-focus background
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