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12/19/2007 12:24:26 AM · #1 |
Okay.....so I want to shoot some Christmas tree lights with "circles of confusion" in them.....how do I do that??? (I'm soooooo confused! LOL)
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12/19/2007 12:42:18 AM · #2 |
I assume you mean the lights will be out of focus. Take a picture of some object that is near to the lens, with the lights a ways off behind the subject. That way the image will appear sharp (because the subject is sharp), but the lights in the image will blossom as the become out of focus.
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12/19/2007 12:43:35 AM · #3 |
Best lens for the job in your profile is the Canon 50mmf1.4 or the Tamron. Setup a chair, and an object on it, say a glass. Use a tripod for this test. Set the chair at least a few feet away, how far the object is from the tree lights also makes for a different effect. Shoot in Aperture Priority. Start shooting shooting at F11, take a shot, then choose F9 take a shot, do this till you reach F1.4 on the 50mm. Then just browse through the pics for the results. A picture is worth a 1000 words ;)
The highlights, the bright spots, when out of focus and depending on the depth of field create that bokeh effect. 
Foil and a light shining on it created those circles for me. I'll digg up the exposure details and post them in the morning. |
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12/19/2007 12:48:45 AM · #4 |
I think this is what you are looking for, right? Something along these lines:
To get this, I'm focused tightly on the bride, shooting at f/2.8 at 105mm. So there is a very narrow depth of field and everything behind her is thrown out of focus.
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12/19/2007 01:33:06 AM · #5 |
| if you want the light to be focused and have the rings around them, shoot it at around f22 for a cupple seconds. mount the camera on a tripod, go to manual focus. take the photo, let it focus for a second and then make it out of focus. |
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12/19/2007 01:38:13 AM · #6 |
Originally posted by amandak:
Okay.....so I want to shoot some Christmas tree lights with "circles of confusion" in them.....how do I do that??? (I'm soooooo confused! LOL)
Thanks! |
I think what you may be describing is bokeh, yes?
"Bokeh" is more of a photographic art term, where as "circle of confusion" is more related to the science of optics.
By the way, you can find the diameter of your camera's CoC here.
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12/19/2007 01:10:13 PM · #7 |
| Wow....thanks for the clarification everyone! Somehow I was under the impression that bokeh and circles of confusion were two different things, but apparently with regards to photography they are basically the same. Yes, David...that's *exactly* the effect (great photo, btw!!). |
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12/19/2007 01:43:24 PM · #8 |
Originally posted by amandak:
Wow....thanks for the clarification everyone! Somehow I was under the impression that bokeh and circles of confusion were two different things, but apparently with regards to photography they are basically the same. Yes, David...that's *exactly* the effect (great photo, btw!!). |
"Circle of Confusion" is the name of an optical phenomenon. It's a highly technical term. It refers to what happens when a lens is stopped down to a very small diameter, so that light bouncing between the leaves of the aperture causes the image, as a whole, to be less sharp than it would be at a larger aperture. Actually, there is a CoC associated with every aperture, but it is more pronounced the more you stop down.
So there's always a tradeoff, sharpness-wise, between DOF and the sharpness of the image. Especially with ultrawide lenses, like my Canon 10-22mm, if you stop down beyond, say, f/8 you get a REALLY tiny aperture and CoC steps in big-time, so the image is nowhere NEAR as sharp as one shot at f/5.6.
"Bokeh" really has nothing at all to do with CoC; it's a term that refers to the "quality" of the OOF areas of the image, and (according to some people) specifically the way the given lens renders specular highlights that are totally OOF. This is what you are talking about in your example; you want that "sweet bokeh" on the OOF lights.
The best way to get it is to open the lens up to make the plane of focus be very narrow. But bear in mind that different lenses produce different qualities of bokeh. If you look closely, you can see some are pentagonal, some are hexagonal, some are circular, etc. This is a function of the physical construction of the aperture, how many leaves are opening/closing. Obviously, the more sides there are to the aperture, the less rectilinear will appear the bokeh.
R.
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12/19/2007 02:57:47 PM · #9 |
Originally posted by Bear_Music:
Originally posted by amandak:
Wow....thanks for the clarification everyone! Somehow I was under the impression that bokeh and circles of confusion were two different things, but apparently with regards to photography they are basically the same. Yes, David...that's *exactly* the effect (great photo, btw!!). |
Lots of info in your post! So, in other words, is bokeh caused by the CoC process? Or isn't it a cause/effect relationship?
"Circle of Confusion" is the name of an optical phenomenon. It's a highly technical term. It refers to what happens when a lens is stopped down to a very small diameter, so that light bouncing between the leaves of the aperture causes the image, as a whole, to be less sharp than it would be at a larger aperture. Actually, there is a CoC associated with every aperture, but it is more pronounced the more you stop down.
So there's always a tradeoff, sharpness-wise, between DOF and the sharpness of the image. Especially with ultrawide lenses, like my Canon 10-22mm, if you stop down beyond, say, f/8 you get a REALLY tiny aperture and CoC steps in big-time, so the image is nowhere NEAR as sharp as one shot at f/5.6.
This explains why my 12-24mm lens isn't nearly as sharp as what I expected it to be at a smaller aperture. Is there some way to determine the "sweet spot" or is it just through trial and error?[/i]
"Bokeh" really has nothing at all to do with CoC; it's a term that refers to the "quality" of the OOF areas of the image, and (according to some people) specifically the way the given lens renders specular highlights that are totally OOF. This is what you are talking about in your example; you want that "sweet bokeh" on the OOF lights.
The best way to get it is to open the lens up to make the plane of focus be very narrow. But bear in mind that different lenses produce different qualities of bokeh. If you look closely, you can see some are pentagonal, some are hexagonal, some are circular, etc. This is a function of the physical construction of the aperture, how many leaves are opening/closing. Obviously, the more sides there are to the aperture, the less rectilinear will appear the bokeh.
[i]Yes, I've seen the different shapes you mention. I'll give it a try this evening with some of my lenses and see how it works out for me.
R. |
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12/20/2007 09:48:28 AM · #10 |
Here's a good article on Bokeh and CoC. //www.kenrockwell.com/tech/bokeh.htm
I've got a different understanding of what CoC is than what was previously posted. The CoC is the circle produced on the imaging plane by a point source of light on the other side of the lens. So CoC describes how much blur there is and does not depend on whether its caused by diffraction or focus issues. See //en.wikipedia.org/wiki/Circle_of_confusion
Diffraction is the result of a small aperture and is caused by the wave-like nature of light. See //www.cambridgeincolour.com/tutorials/diffraction-photography.htm
The "Dr. Quantum" video //video.google.com/videoplay?docid=-4988635765360591842&q=dual+slit+experiment&total=88&start=0&num=10&so=0&type=search&plindex=8
gives you more info.
Message edited by author 2007-12-20 09:48:56. |
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12/20/2007 10:27:35 AM · #11 |
Originally posted by hankk:
I've got a different understanding of what CoC is than what was previously posted. The CoC is the circle produced on the imaging plane by a point source of light on the other side of the lens. So CoC describes how much blur there is and does not depend on whether its caused by diffraction or focus issues. See //en.wikipedia.org/wiki/Circle_of_confusion |
That's not quite right as you have described it; the point of using the "point source" of light to measure CoC is because it's definable and measurable. In other words, when a point source stops being a point source to the eye, the focus is sufficiently off as to be considered "out of focus". This is different from the bokeh being discussed, which is a result of point sources being deliberately thrown way out of focus.
It's hard to lay this out in anecdotal terms that make practical sense. It would appear that you are correct that CoC more properly refers to how much anything is or is not within the zone we call DOF, but the fact remains that in practical terms photographers have used the term to explain why we tend to LOSE sharpness at smaller apertures where we would expect it to increase. And that particular increase in the CoC is due to diffraction.
R.
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12/20/2007 04:03:28 PM · #12 |
Originally posted by Bear_Music:
Originally posted by hankk:
I've got a different understanding of what CoC is than what was previously posted. The CoC is the circle produced on the imaging plane by a point source of light on the other side of the lens. So CoC describes how much blur there is and does not depend on whether its caused by diffraction or focus issues. See //en.wikipedia.org/wiki/Circle_of_confusion |
That's not quite right as you have described it; the point of using the "point source" of light to measure CoC is because it's definable and measurable. In other words, when a point source stops being a point source to the eye, the focus is sufficiently off as to be considered "out of focus". This is different from the bokeh being discussed, which is a result of point sources being deliberately thrown way out of focus.
It's hard to lay this out in anecdotal terms that make practical sense. It would appear that you are correct that CoC more properly refers to how much anything is or is not within the zone we call DOF, but the fact remains that in practical terms photographers have used the term to explain why we tend to LOSE sharpness at smaller apertures where we would expect it to increase. And that particular increase in the CoC is due to diffraction.
R. |
Sorry, that was a poor way for me to phrase it. Thank you for clarifying things.
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