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04/19/2006 03:09:20 PM · #1 |
Took these photos of heron in weeds and thought it would look nice if I framed him with some of the flora surrounding him. Came out good (at least to me), but the leaf (or leaves) in the upper right quadrant seem to turn opaque, almost transparant. I just wondered why/how. Have not noticed this phenomenon on other photos, but admit I could have seen it a dozen times without NOTICING it!! LOL
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Thanks in advance for any and all help. Feel free to comment on how I could have improved the shots too!!
Jacque |
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04/19/2006 03:21:55 PM · #2 |
If the object is close enough to the lens, it will be able to "see around both sides" of the object.
Focus your eye on something across the room, and bring a thin object (e.g. a toothpick) closer to your eye and you'll see it become partially "transparent" as well. |
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04/19/2006 03:22:14 PM · #3 |
I don't know all the technicals but I'll take a shot.
When a relatively small object is close to your lens the light bends around it and, to a varying extent, can make it appear semi-transparent when it is realy vary solid. The effect varies with the distance from your lens, more transparent when closer and less when farther. I have encountered this when shooting thru a chain link fence at the zoo, and also when shooting thru the netting behind homeplate at baseball games. Too make the netting/fence almost disappear put your lens up against it as closely as you can.
Now kirbic can give the proper terminology and explain it in a scientific way.
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04/19/2006 03:22:26 PM · #4 |
It is caused by the object blurring and being spread out a bit -- it blends with what is around it. A good bokeh in the background depends on this, but in the background there is nothing more sharp and in focus than what is seen. This not true of foreground bokeh. The in focus subject behind the out of focus foreground element comes thru -- sometimes very clearly.
Sports photographers very often depend on this. They will sit up just outside the fencen and take the shots without worrying if the fence is going to be going across the subject or not -- it will be so OOF it won't even be visible with a shallow enough DOF.
David
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04/19/2006 03:24:25 PM · #5 |
Originally posted by coolhar:
Now kirbic can give the proper terminology and explain it in a scientific way. |
I think the effect is diffraction ... the slight bending of the light around the edge of the object. |
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04/19/2006 03:24:57 PM · #6 |
Thanks all for your answers, I had seen it with fences, mesh, etc. Had never seen it with something as large as those leaves, did not realize it would work that way with something that large!! Thanks again!
Jacque |
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04/19/2006 03:28:13 PM · #7 |
BTW, you got pretty close to that heron to get those very clear head shots, nice work.
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04/19/2006 03:32:24 PM · #8 |
You can see the same effect quite well on this shot.
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04/19/2006 03:35:49 PM · #9 |
Originally posted by GeneralE:
Originally posted by coolhar:
Now kirbic can give the proper terminology and explain it in a scientific way. |
I think the effect is diffraction ... the slight bending of the light around the edge of the object. |
Actually, diffraction doesn't figure in. It's just the fact that the lens aperture is not infinitely small. Consider a light ray starting from a point on the bird, and passing to straight to the camera, entering at the center of the lens aperture. If the ray passes through the leaf, it will be blocked. Now imagine rays coming from the same point, but entering at the left and right edges of aperture. These may not be blocked, since their path is different.
All these rays are focused at the same spot on the sensor. The end effect is a "fade out" of opacity toward the edge of the intruding leaf, and for a thin object, even the center can become semi-trnasparent.
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04/19/2006 03:39:03 PM · #10 |
Originally posted by kirbic:
Originally posted by GeneralE:
Originally posted by coolhar:
Now kirbic can give the proper terminology and explain it in a scientific way. |
I think the effect is diffraction ... the slight bending of the light around the edge of the object. |
Actually, diffraction doesn't figure in. It's just the fact that the lens aperture is not infinitely small. |
Hey, my first answer was better : )
The lens/aperture combo does just see "around" the object ... |
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04/19/2006 03:41:47 PM · #11 |
| Could be a black hole.... Bending light with huge gravitational force |
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04/19/2006 04:15:40 PM · #12 |
Originally posted by olddj:
Thanks all for your answers, I had seen it with fences, mesh, etc. Had never seen it with something as large as those leaves, did not realize it would work that way with something that large!! Thanks again!
Jacque |
It's not the leaves that you are seeing "around". The vertical curved brownish bar is what is nearer the lens, and it is that bar that you are seeing "around". Look closely at the Heron's beak in the first photo, and you will see that the bar is there, faintly, in front of, not behind the beak. Likewise, it is in front of, not behind, the leaves.
Ron
Message edited by author 2006-04-19 19:47:59. |
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04/19/2006 04:28:55 PM · #13 |
Originally posted by kirbic:
Actually, diffraction doesn't figure in. It's just the fact that the lens aperture is not infinitely small. Consider a light ray starting from a point on the bird, and passing to straight to the camera, entering at the center of the lens aperture. If the ray passes through the leaf, it will be blocked. Now imagine rays coming from the same point, but entering at the left and right edges of aperture. These may not be blocked, since their path is different.
All these rays are focused at the same spot on the sensor. The end effect is a "fade out" of opacity toward the edge of the intruding leaf, and for a thin object, even the center can become semi-trnasparent. |
Thanks kirbic. I guess the effect would become more pronounced with a wider aperture, as I often use in sports shooting.
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04/19/2006 06:07:36 PM · #14 |
Originally posted by coolhar:
Thanks kirbic. I guess the effect would become more pronounced with a wider aperture, as I often use in sports shooting. |
Yep. And it's the physical aperture size that matters, not the f-stop, so at 200mm & f/2.8 (71mm effective aperture) the effect will be greater than at 100mm & f/2.8 (36mm effective aperture). That's assuming the same distances to subject and intervening object, though, so the framing on the 200m shot will be much tighter than the 100mm shot.
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04/19/2006 06:24:06 PM · #15 |
kirbic the only thing that amazes me more than the amount of knowledge you possess is your wiliness to share it.
Thanks
Message edited by author 2006-04-19 18:24:29.
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