DOF & Shutter Speed


kohbro

New Member
Dec 30, 2011
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#1
Hi there! Will shutter speed affect the DOF? For example, if I have a perfect exposure at ISO 100; f/1.8; 1/90sec; subject distance of 1m, will changing the ISO to 800, shutter speed to 1/720 but all else remaining the same affect the DOF?

All comments, opinions and 2 cents worth will b very much appreciated. And if u tink this is a stupid question, just humour me,pls. Cheers!
 

Rashkae

Senior Member
Nov 28, 2005
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#2
No. Shutter speed has no effect on DOF. BTW, you can test this yourself anytime on your own instead of asking here.
 

kohbro

New Member
Dec 30, 2011
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#3
Hi there! Will shutter speed affect the DOF? For example, if I have a perfect exposure at ISO 100; f/1.8; 1/90sec; subject distance of 1m, will changing the ISO to 800, shutter speed to 1/720 but all else remaining the same affect the DOF?

All comments, opinions and 2 cents worth will b very much appreciated. And if u tink this is a stupid question, just humour me,pls. Cheers!
 

kohbro

New Member
Dec 30, 2011
156
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0
#4
Thanks for ur reply. Tried it on my Canon 550D with a 50mm f1.8. Couldnt tell the diff. So tot i'd ask ard, incase my equipment is not good enuf to register the difference.
 

rahulv

New Member
Jul 27, 2011
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#7
aperture, focal length and distance of subject from the lens (inverse relation); only these three things control depth of field
 

David Kwok

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Aug 23, 2008
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#9
rahulv said:
aperture, focal length and distance of subject from the lens (inverse relation); only these three things control depth of field
Partially correct, add on CoC too. I believe CoC is contributed by both the resolution of the lens and also the density of the sensor.
 

Octarine

Moderator
Staff member
Jan 3, 2008
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#10
Partially correct, add on CoC too. I believe CoC is contributed by both the resolution of the lens and also the density of the sensor.
Then we also have to add sensor size here. But since these factors are not changeable by TS during shooting we can safely skip them here. They are constants.
 

kohbro

New Member
Dec 30, 2011
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#11
U guys had me at CoC.... ;p anyways, thanks for all the links and info.

Another question. Can the below terms b used interchangeably?

Shallow DOF; Bokeh; Background blur.

And a very Happy New Year to all too.
 

surrephoto

Senior Member
Jan 14, 2009
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#12
U guys had me at CoC.... ;p anyways, thanks for all the links and info.

Another question. Can the below terms b used interchangeably?

Shallow DOF; Bokeh; Background blur.

And a very Happy New Year to all too.
Related terms but all different.

Shallow DOF refers to the depth-of-field being small and less things/area/part of the image are said to be in focus.

Bokeh is the rendition of out-of-focus highlights but can also refer to background blur in some context. It does not mean that images at a smaller aperture/large dof can't have bokeh. Some photographers are sensitive about the exact term and the meaning so I try not use it. We can describe the shape of bokeh highlights with terms such as "perfectly round", "cats-eye", "plain ugly", "nervous" and even "onion".

Background blur is of course the literal bluriness of the background. To differ from the term bokeh, it usually does not refers to round "bokeh" highlights, but the shape and aesthetic value of these highlights can indirectly or directly affect the quality of background blur. We use words such as "smooth", "harsh", "nervous", "creamy", "dream-like" and misleading words such as "pop" and "3D effect" to describe background blur quality.
 

Rashkae

Senior Member
Nov 28, 2005
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#13
Related terms but all different.

Shallow DOF refers to the depth-of-field being small and less things/area/part of the image are said to be in focus.

Bokeh is the rendition of out-of-focus highlights but can also refer to background blur in some context. It does not mean that images at a smaller aperture/large dof can't have bokeh. Some photographers are sensitive about the exact term and the meaning so I try not use it. We can describe the shape of bokeh highlights with terms such as "perfectly round", "cats-eye", "plain ugly", "nervous" and even "onion".

Background blur is of course the literal bluriness of the background. To differ from the term bokeh, it usually does not refers to round "bokeh" highlights, but the shape and aesthetic value of these highlights can indirectly or directly affect the quality of background blur. We use words such as "smooth", "harsh", "nervous", "creamy", "dream-like" and misleading words such as "pop" and "3D effect" to describe background blur quality.
Sorry I have to disagree a bit, especially on the section in bold...

Bokeh IS NOT just about highlights. Bokeh is the quality of the out-of-focus areas and blur and how it enhances/complements the subject or distracts from it.

Bokeh can be "smooth", "harsh", "nervous", "creamy", "dream-like". Bokeh highlights can have harsh edges (ni-sen bokeh) through to even through to the "preferred" smooth fall-off.

So, to conclude:

1. Shallow DOF: just a measure of how much of the image is in sharp focus
2. Background blur: Just that - the background is blurred. You could say "very blurred" or "not enough blur"
3. Bokeh: The aesthetic quality of the blur itself, and how it enhances or distracts from the subject.

"Pop" and "3D effect" are NOT used to describe background blur quality, they are just ways to describe very nice subject isolation with good microcontrast.

Background blur is just that - blurred background.
 

Last edited:

David Kwok

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#14
Octarine said:
Then we also have to add sensor size here. But since these factors are not changeable by TS during shooting we can safely skip them here. They are constants.
I don't believe the sensor size matters. But we are going this direction, then of course it will dwell into a few weeks back when there is a heated discussion between sensor size and perspective and DOF. It is actually the sensor density that affect the CoC and hence the DOF.

You are pretty right it is almost a constant so to speak if we are dealing with a single gear and single viewer's eye. In any case what I was trying to mention is what is still not considered and can be considered into the equation. If there is an assumption already mentioned, then what I mentioned will be over defined, but clearly there isn't. :)
 

surrephoto

Senior Member
Jan 14, 2009
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#15
Sorry I have to disagree a bit, especially on the section in bold...

Bokeh IS NOT just about highlights. Bokeh is the quality of the out-of-focus areas and blur and how it enhances/complements the subject or distracts from it.

Bokeh can be "smooth", "harsh", "nervous", "creamy", "dream-like". Bokeh highlights can have harsh edges (ni-sen bokeh) through to even through to the "preferred" smooth fall-off.

So, to conclude:

1. Shallow DOF: just a measure of how much of the image is in sharp focus
2. Background blur: Just that - the background is blurred. You could say "very blurred" or "not enough blur"
3. Bokeh: The aesthetic quality of the blur itself, and how it enhances or distracts from the subject.

"Pop" and "3D effect" are NOT used to describe background blur quality, they are just ways to describe very nice subject isolation with good microcontrast.

Background blur is just that - blurred background.
Hi rashkae, the terms are very confusing so I cannot deny that i must have got something wrong somewhere.

Thats why I state that the words "pop" and "3D effect" are misleading. A surprising number of people related 3D effect directly to background blur. I'm aware that micro-contrast does affect 3D effect but as you stated "very nice subject isolation" which is directly related to quality of background blur, and quality of blur near to the DOF. Spherical & other aberrations can affect this. Nice background blur can have what some people deem as bad bokeh. Imagine the 85L & 50L from canon have fish-eye bokeh which is unacceptable for some people, but the blur quality is inherently very good (smooth).
 

Rashkae

Senior Member
Nov 28, 2005
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#16
Hi rashkae, the terms are very confusing so I cannot deny that i must have got something wrong somewhere.

Thats why I state that the words "pop" and "3D effect" are misleading. A surprising number of people related 3D effect directly to background blur. I'm aware that micro-contrast does affect 3D effect but as you stated "very nice subject isolation" which is directly related to quality of background blur, and quality of blur near to the DOF. Spherical & other aberrations can affect this. Nice background blur can have what some people deem as bad bokeh. Imagine the 85L & 50L from canon have fish-eye bokeh which is unacceptable for some people, but the blur quality is inherently very good (smooth).
You are limiting your definition of bokeh to just the highlights. That's what's wrong. Bokeh is NOT just the highlights, it's the quality of the entire blur, from the background to the highlights. Most importantly, does it complement or detract from the subject. In your example, let's say the overall background is creamy, but there are harsh highlights that distract from the subject, or the "fisheye" rendering, but it can STILL be "good bokeh" if it complements the subject. If it distracts, then it's bad bokeh, even if the overall background rendering is smooth.

As for the "3D effect", etc, this is actually independent of bokeh or the quality of the background blur. You can have great subject isolation, but cruddy bokeh. That's why composition is important. :)
 

daredevil123

Moderator
Staff member
Oct 25, 2005
21,662
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lil red dot
#17
David Kwok said:
I don't believe the sensor size matters. But we are going this direction, then of course it will dwell into a few weeks back when there is a heated discussion between sensor size and perspective and DOF. It is actually the sensor density that affect the CoC and hence the DOF.

You are pretty right it is almost a constant so to speak if we are dealing with a single gear and single viewer's eye. In any case what I was trying to mention is what is still not considered and can be considered into the equation. If there is an assumption already mentioned, then what I mentioned will be over defined, but clearly there isn't. :)
Yes. Sensor size do not matter. When using a larger sensor camera, what happens is the subject distance is closer giving shallower dof.

What matters is pixel size. Which is what affects CoC.
 

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