Depth of Field Question
Sep 4, 2015 10:58:56 #
For the sake of argument, let's say I'm using a 100mm Prime lens on my camera. I position the camera to frame the subject to my liking. I use a fairly open aperture for a shallow depth of field (let's say f5.6). I then focus my lens on the subject.
Now, will the Depth of Field window be set to showcase my subject because that is the center of my focus, or do I have to adjust my camera position in relation to the subject to get my subject correctly in the Depth of Field using an aperture of f5.6.
Ultimately I think what I'm asking is, what moves the Depth of Field forward or backward in the frame, the focus of the lens or the focal length of the lens?
Now, will the Depth of Field window be set to showcase my subject because that is the center of my focus, or do I have to adjust my camera position in relation to the subject to get my subject correctly in the Depth of Field using an aperture of f5.6.
Ultimately I think what I'm asking is, what moves the Depth of Field forward or backward in the frame, the focus of the lens or the focal length of the lens?
Sep 4, 2015 11:09:34 #
Lenses used to have distance scales that showed what would be in focus based on the f-stop and the distance of the object. The further away something is away the more in focus everything is at a fairly shallow or mid f-stop. Focal length, f-stop and distance are what effect depth of field.
Remember you can always check what is in focus at a given f-stop by using the depth of field preview on you camera. This closes the iris with firing the shutter to give an idea of what will be in focus when the lens is stopped down for the exposure.
Remember you can always check what is in focus at a given f-stop by using the depth of field preview on you camera. This closes the iris with firing the shutter to give an idea of what will be in focus when the lens is stopped down for the exposure.
Sep 4, 2015 11:15:47 #
The focus point locates the mid point of the depth of field; the aperture increases or decreases it, as does the focal length.
Sep 4, 2015 11:16:28 #
Picdude wrote:
For the sake of argument, let's say I'm using a 10... (show quote)
The focus of the lens sets the "zero" point for DOF. Generally the DOF is 1/3 in front of that point and 2/3 behind.
Lens mm affects the range of the DOF but not the zero point.
Sep 4, 2015 11:21:29 #
Big Bill
Loc: Phoenix, AZ
andypop wrote:
The focus point locates the mid point of the depth of field; the aperture increases or decreases it, as does the focal length.
As does the distance to the subject.
Closer, less DOF.
Farther, more DOF.
Sep 4, 2015 11:23:27 #
Darkroom317 wrote:
Lenses used to have distance scales that showed wh... (show quote)
I agree with all of the above. So - Using a given Focal Length, given Aperture and without repositioning the camera - Can I move the Depth of Field window from the Foreground of the frame to the Background of the frame simply by changing my focus on a subject either in the Foreground or the Background?
Sep 4, 2015 11:30:07 #
Picdude wrote:
I agree with all of the above. So - Using a given Focal Length, given Aperture and without repositioning the camera - Can I move the Depth of Field window from the Foreground of the frame to the Background of the frame simply by changing my focus on a subject either in the Foreground or the Background?
on pain of over simplification: yes, that is how it works
stop and focl length change the depth of the depth of field, focus changes center.
see andypop above
Sep 4, 2015 11:37:20 #
Picdude wrote:
For the sake of argument, let's say I'm using a 10... (show quote)
Hello
Go to this site(s) below this will help you find what your looking for.
http://www.dofmaster.com/dofjs.html
http://blog.berniesumption.com/photography/better-depth-of-field-table/
Sep 4, 2015 11:43:35 #
andypop wrote:
The focus point locates the mid point of the depth of field; the aperture increases or decreases it, as does the focal length.
MtnMan wrote:
The focus of the lens sets the "zero" point for DOF. Generally the DOF is 1/3 in front of that point and 2/3 behind.
Lens mm affects the range of the DOF but not the zero point.
Lens mm affects the range of the DOF but not the zero point.
Shortly after I posted this question I started thinking about focus stacking and the steps needed to set that up, at which point I figured I had answered my own question - the same way the two of you answered above. MtnMan, thank you for the 1/3 - 2/3 generalization. Next time I have a 'Senior Moment' I'll try to give myself some more time before punching the UHH panic button :D . On the other hand, hopefully this helps someone else out with Depth of Field as well.
Sep 4, 2015 11:53:45 #
MtnMan wrote:
The focus of the lens sets the "zero" point for DOF. Generally the DOF is 1/3 in front of that point and 2/3 behind.
That is not generally true...
For example, a 100mm f/1 lens focused at 1 meter will have DOF that is almost precisely equally spread in front and in back of the true focus point. When focused at 10 meters there will be a slightly larger distance in back. Focused at 110 meters it will be almost exactly 1/3 and 2/3 as you suggest. When focused at 335 meters about half the distance in front (167 meters) will be within the front DOF, but to the rear everything to infinity is in focus.
If very much depends on what the actual focus distance is and on what the focal length and aperture are. Note that the same 100mm lens that provides the 1/3 to 2/3 ratio at f/1 focused at 110m, when stopped down to f/22 has DOF from 87 meters in front all the way to infinity.
Sep 4, 2015 12:06:28 #
RichardSM wrote:
Hello
Go to this site(s) below this will help you find what your looking for.
http://www.dofmaster.com/dofjs.html
http://blog.berniesumption.com/photography/better-depth-of-field-table/
Go to this site(s) below this will help you find what your looking for.
http://www.dofmaster.com/dofjs.html
http://blog.berniesumption.com/photography/better-depth-of-field-table/
Thanks for the links, especially the Better Depth of Field tables. Will be printing those out for future reference.
Sep 4, 2015 12:16:30 #
fine on the depth tables, but since focus degrades gradually from the focal point and there is the "preview" button on the camera, maybe we shudda left that gremlin,left over from the film days,in his jar?
Sep 4, 2015 12:21:02 #
EdM wrote:
fine on the depth tables, but since focus degrades gradually from the focal point and there is the "preview" button on the camera, maybe we shudda left that gremlin,left over from the film days,in his jar?
Gremlin?
Sep 4, 2015 12:23:45 #
Sep 4, 2015 14:37:00 #
Picdude wrote:
For the sake of argument, let's say I'm using a 10... (show quote)
The focal length does not change the depth of field. Quality zooms retain their focus whether zoomed in or out. You determine the depth of field position with focus and retain it until either changing the focus or the aperture setting.
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