Questions on DOF


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Camm

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#1
Hi,

How can I achieve sharp object with very soft/blur background? I've read somewhere that by setting aperture to its largest to achieve that but my camera still can't seems to achieve that DOF, unless I shoot in Macro. Is there any other settings that I've missed?
 

jnet6

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Apr 21, 2004
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#2
yr distance with the subject and the subject between the background plays a part.
next is the lens.
2nd is the focal length.
 

CasonLyn

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Apr 18, 2006
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#4
Hi Camm,

Assume you are using compact digicam? The sensor size of a compact is too small to achieve the shallow DOF, I was using a compact b4 and also used full zoom, macro to achieve decent shallow DOF.

Now that I've upgraded to DSLR, i dun have that limitation anymore :)
 

singscott

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#5
CasonLyn said:
Hi Camm,

Assume you are using compact digicam? The sensor size of a compact is too small to achieve the shallow DOF, I was using a compact b4 and also used full zoom, macro to achieve decent shallow DOF.

Now that I've upgraded to DSLR, i dun have that limitation anymore :)
Yes the sensor size does play a part it is call COC, Circle Of Confusion
 

compro_1975

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Apr 24, 2005
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#6
CasonLyn said:
Hi Camm,

Assume you are using compact digicam? The sensor size of a compact is too small to achieve the shallow DOF, I was using a compact b4 and also used full zoom, macro to achieve decent shallow DOF.

Now that I've upgraded to DSLR, i dun have that limitation anymore :)
u mean, for compact cam, i change to micro mode, can take a pix with the background blur/soft???:D
 

jnet6

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#7
compro_1975 said:
u mean, for compact cam, i change to micro mode, can take a pix with the background blur/soft???:D
negative, depends where yr subject is position to yr camera.
 

CasonLyn

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Apr 18, 2006
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#8
jnet6 said:
negative, depends where yr subject is position to yr camera.
Yep, when using compact, tend to get the shallow DOF only when I'm close to the subject. Which is why I use Macro mode.
 

Kip

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Feb 23, 2005
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#9
As others have mentioned, depth of field depends on:

1. Imaging sensor size (film or digital)
2. Lens focal length
3. Distance to subject

In general, the closer to the subject, the shallower the depth-of-field for a given imager and focal length. Hence why you have shallower depth of field when you get close to your subject. "Macro mode" is just a way of telling the camera to allow you to focus really close to the subject.

Additionally, the smaller the f-stop (larger the aperature), the shallower the depth-of-field.

And the longer the focal length (at the same subject distance) the shallower the depth-of-field.

You may find the following link to an online depth-of-field calculator of interest. Good to get an idea of how all the variables relate. Note that circle of confusion is related to the size of the imager in your camera.

http://www.dofmaster.com/dofjs.html

In addition to the technical aspects of depth-of-field, you will find that different lens produce a different quality or aethestic to the out-of-focus area. This is often called bokeh
. The word "bokeh" comes from the Japanese word "boke" (pronounced bo-keh) which literally means fuzziness or dizziness. It is a function of the lens design and you will find (in the SLR world) people discussing the quality of the bokeh.

You may find the following link interesting: http://www.kenrockwell.com/tech/bokeh.htm

Happy shooting,

--Kip
 

singscott

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Aug 25, 2004
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#12
Artosoft said:
CoC is to determine how blur is blur.

http://en.wikipedia.org/wiki/Circle_of_confusion

Regards,
Arto.
This so funny let me quote something from there.

"1. To calculate a camera's depth of field, one needs to know how large a circle of confusion can be considered to be an acceptable focus. The maximum acceptable diameter of such a circle of confusion is known as the maximum permissible circle of confusion, the circle of confusion diameter limit, or the circle of confusion criterion, but is often incorrectly called simply the circle of confusion."

To calculate a camera DOF is on number one. But you half right. Read it carefully you will find a lot this DOF calculation, determinding how much blur acceptable in the focus image circle and the size of these circle create different blurness.

Oh by the way blurness here mean things that is out DOF...........:think: ;)
 

singscott

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#13
Artosoft said:
CoC is to determine how blur is blur.

http://en.wikipedia.org/wiki/Circle_of_confusion

Regards,
Arto.
A good thing have come out of this. To show my point that film and sensor size does play a part on DOF. Go to the above link and look for the table where they show Film format, Frame size, CoC. Ok how to know there more DOF or lesser. COC is about blurness or our term shallow DOF because if there more COC, less area will be in focus or less DOF. You will see the bigger the film size, the bigger the COC number. Oh those numbers just to show this relation between film size, COC and DOF. Base on "Accepted values for circle of confusion based on d/1500" or layman term "sample math calculation", so dun read too much into the number. But main point is to see the COC number getting bigger. So thank you Arto for point out this very useful web site to show my point. In fact if you a photography tech nut, all the useful information about COC is there. But when I tell people it will be there something call COC it is related to DOF and the sensor size, hope you understand:sweatsm:
 

zoossh

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Nov 29, 2005
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#15
Camm said:
Hi,

How can I achieve sharp object with very soft/blur background? I've read somewhere that by setting aperture to its largest to achieve that but my camera still can't seems to achieve that DOF, unless I shoot in Macro. Is there any other settings that I've missed?
if u used a DSLR

1. use a tele zoom lens at the longer focal length
2. put your object near to you and far from the background
3. set your largest aperture.
 

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