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Deviousness `anmari has been spreading her infectious positivity throughout our community for over 6 years. Throughout this time Ana has been at the core of all things devious, passionately developing an eclectic gallery, helping organise devmeets, participating in chat events and also recently completed dedicating her time as a Community Volunteer. We are absolutely delighted to bestow the Deviousness Award for May 2013 to `anmari, congratulations! Read More
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Sta.sh
[link]
have fun with that link
And yeah, it's call bokeh, and out of focus highlights, and circles of confusing, and etc. It has too many names
lenses do not make points of light...ever. What they do make is very tiny circles that look like points of light. A picture like this, taken with a 500mm reflex lens, will actually show the circles. (other lens may work, but I have only tried it with a reflex.)
Let me try to explain: (it has been a long time so I have had to refer to some of my material))
technically a "perfect lens" can only focus on one object plane at a time. When the lens is perfectly focuses, each point of light in the object plane has been brought together to form a point, however, the point is really a cone of light and if the distance between the image plane (film of CMOS) is increased or decreased the points of light will become cones again. So ever place there the light hitting the film plane is not in focus would be a small circle. Now remember we are talking about a "PERFECT" lens, which does not exist in reality.
the size of a circle is affected by:
focal length. The shorter the lens, the smaller the circles and the longer the lens the larger the circles.
Aperture - smaller apertures produce smaller circles
The distance between the plane of focus and other object planes. the shorter the distance, the smaller the circles.
the distance between the object plane and the lens. the greater the distance the smaller the circles.
the resolving power of the lens. The better corrected it is, the smaller the circles will be. (In your picture, you cannot really see the circles, that is because of the quality of the lens you have. It is well corrected.) (In the 500mm lens I used, while it was of professional quality, was built in the 80's, it was a fixed aperture of f8 and was a reflex lens, all of which would result in greater difficulty for correction). A reflex lens is one in which the light bounces inside through the use of mirrors doubling up on itself to produce a longer lens in a compact form).
Ok..thatis aboutit.
so if you want to see the circles of confusion..use a wide aperture and a long lens\ perferably one that is not well corrected.
So I just tried a Sigma 500mm lens. It could not get any circles. Which means, that if you want to see them, you might have a hard time given the quality of the lenses available today.
Ok so here is the bad news, I just tried ever lens (and camera from 120 to 6x7) I own, digital and conventional, I even used older lenses with double 2x converters and i could not get it to happen. Maybe one needs a reflex lens because lens construction and correction is so good.
Well, thanks for the excellent and through explanation and background of what the term "circles of confusion" means. I'll be sure to put that in a research paper some day