sirius
Well-known
ferider
Veteran
If you look at a single OOF highlight in the background, it will not be a circle, but an ellipses, usually shorter radially than tangentially. Looking at many of those looks like circles around the picture center. (forgive any misspellings)
You can google "comatic aberration" for more details.
You can google "comatic aberration" for more details.
Pirate
Guitar playing Fotografer
"chromatic aberration"
;-)
;-)
Chromatic Aberration and "Comatic Aberration" are completely different. The latter is more commonly referred to as simple "coma". But in a book on optics, the term "comatic aberration" is used.
Chromatic Aberration will not cause the ellipses. A debate can ensue on which "lens defects" and combinations of optical defects cause it, whether coma, astigmatism, or vignetting. The short answer: it is caused by the lens not being optically perfect.
Over correction of spherical aberration cause the rims of the circles to be brighter than the center. Everyone can usually agree on that.
Chromatic Aberration will not cause the ellipses. A debate can ensue on which "lens defects" and combinations of optical defects cause it, whether coma, astigmatism, or vignetting. The short answer: it is caused by the lens not being optically perfect.
Over correction of spherical aberration cause the rims of the circles to be brighter than the center. Everyone can usually agree on that.
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sirius
Well-known
Thanks for the ideas. I guess what I am really wondering about is what's often called the circles of confusion. Why do those always happen with backlit leaves and trees?
In this photo I think it is a negative. It has a sort of dazed feeling which detracts from the subject. But, I imagine there are cases where these circles help.
Yes, the circles/ovals are distorted in this photo. I guess that the Leica glass wasn't designed to avoid these things yet. I know with my more impressive Canon lenses the circles are very circular and don't distort like this.
regards
In this photo I think it is a negative. It has a sort of dazed feeling which detracts from the subject. But, I imagine there are cases where these circles help.
Yes, the circles/ovals are distorted in this photo. I guess that the Leica glass wasn't designed to avoid these things yet. I know with my more impressive Canon lenses the circles are very circular and don't distort like this.
regards
Canon 50/1.8, wide-open on the Canon Vt.
Canon 50/1.2 on the M8, wide-open.
You will find most fast lenses will distort the OOF areas. Scene content, F-Stop, distance to the subject, and distance to the background contribute to the effect.
You will find most fast lenses will distort the OOF areas. Scene content, F-Stop, distance to the subject, and distance to the background contribute to the effect.
Collapsible Summicron at F2.
Collapsible Summicron at F4.
Collapsible Summicron at F4.
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JoeV
Thin Air, Bright Sun
The OOF circles are usually in the shape of your lens aperture, plus some diffraction effects making the edges soft. Those that are off-axis can often be elliptical, since the aperture effectively appears elliptical from an off-axis viewpoint. Some lens designs accentuate this off-axis-elliptical effect more than others; in extreme cases this is known as "swirly bokeh."
The quality of light distribution within the OOF circles (i.e. toroid, center-weighted, edge-weighted, etc.) is what is termed 'bokeh'. Although that's the subject for another (probably lengthy and argumentative and pointless) thread.
You may have also noticed that the image of the sun, projected through gaps in tree leaves and projected onto the ground, appear circular. This is because the gaps in the leaves are acting like crude pinhole lenses, projecting an image of the (round) sun. During solar eclipses you can see these projected images turn into crescent-shaped slivers as the eclipse progresses.
~Joe
The quality of light distribution within the OOF circles (i.e. toroid, center-weighted, edge-weighted, etc.) is what is termed 'bokeh'. Although that's the subject for another (probably lengthy and argumentative and pointless) thread.
You may have also noticed that the image of the sun, projected through gaps in tree leaves and projected onto the ground, appear circular. This is because the gaps in the leaves are acting like crude pinhole lenses, projecting an image of the (round) sun. During solar eclipses you can see these projected images turn into crescent-shaped slivers as the eclipse progresses.
~Joe
sirius
Well-known
Thanks JoeV, informative! ...and funny.
Brian Sweeney, not sure if you were trying to do it, but that is the same lens I used for the portrait posted at the top: the 50mm summicron collapsible. In the black and white image above the out-of-focus area is distracting, but I have to admit that it can be lovely, especially in contrast to the modern DSLR look you see so much these days.
Brian Sweeney, not sure if you were trying to do it, but that is the same lens I used for the portrait posted at the top: the 50mm summicron collapsible. In the black and white image above the out-of-focus area is distracting, but I have to admit that it can be lovely, especially in contrast to the modern DSLR look you see so much these days.
Attachments
Those portraits are beautiful, as is the bride.
The collapsible Summicron is my favorite of the classic Leica lenses. The Rigid is sharper, more controlled. I believe it was their first lens designed using a computer.
The older lenses tended to gain sharpness through over-correction of spherical aberration. That turns OOF circles into donuts. Modern lens design corrects much of that. Aspheric optics bring a new dimension to lens design. The advantages were known decades before the first lenses were completed, but the design and manufacturing of the aspheric lens was not possible for the technology of the day.
The collapsible Summicron is my favorite of the classic Leica lenses. The Rigid is sharper, more controlled. I believe it was their first lens designed using a computer.
The older lenses tended to gain sharpness through over-correction of spherical aberration. That turns OOF circles into donuts. Modern lens design corrects much of that. Aspheric optics bring a new dimension to lens design. The advantages were known decades before the first lenses were completed, but the design and manufacturing of the aspheric lens was not possible for the technology of the day.
85/2.8 Sonnar @ f/2.8, Portra 160VC
