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12/10/2003 08:51:36 AM · #1 |
As stupid as it can seem, this is my question.
I've been experimenting with depth of field. I know it depends of the aperture, but I've read it also depends of the focal lenght. Can someone explain?
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12/10/2003 08:54:37 AM · #2 |
| in a nutshell, focal length is the 'zoom factor'. |
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12/10/2003 08:56:38 AM · #3 |
Originally posted by jmsetzler:
in a nutshell, focal length is the 'zoom factor'. |
That's a very small nutshell, John.
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12/10/2003 08:57:50 AM · #4 |
It is the distance from the lens element to the film ( or sensor ) plane. Here is a link to a glossary at the Canon site //www.usa.canon.com/eflenses/lens101/glossary/index_d.html
Message edited by author 2003-12-10 14:03:05.
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12/10/2003 09:16:54 AM · #5 |
And although I posted yesterday that Depth of Field varies by the focal length of a lens, some dispute that wording, stating more accurately that the DOF varies based only on differences in camera-to-subject distance and target image size. A wide angle (small focal length) captures more of a picture "in focus" because it hides the lack of sharpness in a reduced image size.
Here is another link with more detailed info on Depth of Field.
Message edited by author 2003-12-10 14:39:35. |
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12/10/2003 09:22:02 AM · #6 |
Originally posted by jmsetzler:
in a nutshell, focal length is the 'zoom factor'. |
Focal Length is the "Zoom Factor", because if you´re increasing the distance of your lens elements fron your CCD you are projecting a greater image than your sensor. Of course, your CCD can´t see a greater part of this image, croping the bound you have your enlarged or zoomed image where the subject apear to be next to the lens.
In some cameras you have the focus length too. But are things completelly diferent. |
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12/10/2003 09:34:44 AM · #7 |
| Focus length is the distance to the subject. That is the third element of depth of field :) |
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12/10/2003 10:53:54 AM · #8 |
Originally posted by jmsetzler:
Focus length is the distance to the subject. That is the third element of depth of field :) |
Excatly! Focus length is a distance between your camera lens and your subject. That is why you put the focus to infinite and can´t do nothing else to decrease DOF. In this case the DOF is in the infinity too!
But...in what is based these lens distance? In the distance of lens focus element, the front or the rear element? Just I´m curious. I had take some meterings based on both the end and the begining of my lenses and calculated the DOF, after it put the objects in the DOF and out of it and take a photo. I had great diference in results. My lenses are fixed in both, the focal length and focus length to this test. |
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