OOF blur/bokeh quality when focusing to infinity


ijnek

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#1
I had a good read on this forum regarding this OOF blur relating to when a lens focuses to infinity , but i jus can't seem to be able to find the thread now.

can some1 help me?

eg, when the lens focus to infinity on the subject, can i expect nice bokeh quality from the lens or will be background be simply Out of Focus blur?
 

Rashkae

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Nov 28, 2005
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#2
Bokeh depends on lens characteristics and image composition. Focusing to infinity, etc, has nothing to do with bokeh.
 

ijnek

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#3
i hv uploaded 2 photos here....
same shutter speed and aperature value, jus different focusing distance

pic 1, focusin not to infinity.

DSC_1371 by ijnek, on Flickr

pic 2, focusing distance at infinity

Focus distance infinity by ijnek, on Flickr

look at the same area, the left leg the mouse behind it.
in pic 1, the mouse clearly is more blur compare to the 1 in pic 2...

probably my question should hv been DOF when focusing to infinity...
 

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Octarine

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Jan 3, 2008
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#4
Do read up about the basics of Depth of Field and the contributing factors. Pay attention to focal length :) - Use the many online calculators and compare the results.
 

Aug 23, 2010
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#5
distance to subject & distance from subject to background plays a part in determining your oof blur as well
 

Jan 1, 2013
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#6
That right! Same shutter speed and aperture value also doesn't give you the same exposure when u zoom in...
 

ijnek

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#7
thx...i found the point tat i'm tryin to confirm.

Depth Of Field and camera to object distance - The second control you can employ to control depth of field is the distance between the camera and the object you are shooting. The greater this distance is the more depth of field you will have.

will probably confirm y i need a 85mm etc for a full body portrait instead of using a 50mm
 

daredevil123

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Oct 25, 2005
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#8
pic 2, focusing distance at infinity

Focus distance infinity by ijnek, on Flickr

look at the same area, the left leg the mouse behind it.
in pic 1, the mouse clearly is more blur compare to the 1 in pic 2...

probably my question should hv been DOF when focusing to infinity...
You sure the 2nd pic is focused to infinity?

From the EXIF of Pic 2
Focus Distance 2.51 m

Doesn't look like focused to infinity to me. Actually it shows in your pic... how can the lens be focused to infinity if the things behind the toy are blur?


thx...i found the point tat i'm tryin to confirm.

Depth Of Field and camera to object distance - The second control you can employ to control depth of field is the distance between the camera and the object you are shooting. The greater this distance is the more depth of field you will have.

will probably confirm y i need a 85mm etc for a full body portrait instead of using a 50mm
DOF is affected by 4 things only:

1. Focus distance: not necessarily subject to camera distance, the distance to camera from the point where the lens is focused on.
2. Aperture used
3. Focal length
4. Circle of confusion: Explanation here

I had a good read on this forum regarding this OOF blur relating to when a lens focuses to infinity , but i jus can't seem to be able to find the thread now.

can some1 help me?

eg, when the lens focus to infinity on the subject, can i expect nice bokeh quality from the lens or will be background be simply Out of Focus blur?
When you really focus to infinity, there will be NO background blur. Because everything far away will look sharp to you. But you might get some foreground blur, if the foreground is too close to you.

This picture is shot at F3.5 at around 45mm focal length, focused to infinity. Notice how everything looks to be in focus. Why I chose such a large aperture? Simply because I did not bring my tripod with me. So I have to up my ISO and open up my aperture to get a fairly fast shutter speed. And at the same time, I know that since the elements in my picture are all in infinity range for the lens, I can get it all sharp at F3.5. Even if I used F2.8, the picture would have been reasonably sharp.
 

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ijnek

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#9
thx dd123, i'm quite sure it's at inifinity as i'm using the 50mm and i checked the focusin shows it's at infinity.
if i remember correctly, the marking shows it's at inifinity which i checked b4 snappin the pic.

also, ur pic helped me a lot to understand this better.

at this point, i'm quite sure that when focus to infinity, the back ground will b sharp and bokeh effect will hardly b there.
which is y I should hv a longer focal length length if i wan to do a full body portrait pic with bokeh effect.
the 50mm would not be suitable as i would need to be further away from subject and the distance to subject might be at infinity....

thx and do correct me if i'm wrong again
 

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daredevil123

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#10
thx dd123, i'm quite sure it's at inifinity as i'm using the 50mm and i checked the focusin shows it's at infinity.
if i remember correctly, the marking shows it's at inifinity which i checked b4 snappin the pic.

also, ur pic helped me a lot to understand this better.

at this point, i'm quite sure that when focus to infinity, the back ground will b sharp and bokeh effect will hardly b there.
which is y I should hv a longer focal length length if i wan to do a full body portrait pic with bokeh effect.
the 50mm would not be suitable as i would need to be further away from subject and the distance to subject might be at infinity....

thx and do correct me if i'm wrong again
The focus scale markings is iffy because it is not linear. It might seem you are at infinity mark but slightly off only you will be at 3m or so... i am very sure your lens at pic 2 is not at infinity.

You should try at least 135mm or even something like 180 or 200mm if you want good background blur for full body.
 

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Rashkae

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Nov 28, 2005
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#11
thx dd123, i'm quite sure it's at inifinity as i'm using the 50mm and i checked the focusin shows it's at infinity.
if i remember correctly, the marking shows it's at inifinity which i checked b4 snappin the pic.

also, ur pic helped me a lot to understand this better.

at this point, i'm quite sure that when focus to infinity, the back ground will b sharp and bokeh effect will hardly b there.
which is y I should hv a longer focal length length if i wan to do a full body portrait pic with bokeh effect.
the 50mm would not be suitable as i would need to be further away from subject and the distance to subject might be at infinity....

thx and do correct me if i'm wrong again
Uhm. There is no "bokeh effect". Next, if you want to do a full-body portrait and want to blur the background, then shoot at a large aperture (such as f/2.8) and focus on the subject and make sure there is good distance to the background (a few meters).

I don't know why you are even bringing infinity focus into this. Also, if the subject distance is at infinity... do you know what infinity means? ;-)
 

ijnek

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#12
thx dd123.

that was 1 point i was tryin to tell another guy...cos the talk was if he has a 50mm, can't he just take lots of steps back to snap a full body shot with bokeh effect.it's a a dx body, so the view is narrower and he need more distance for a full body shot.

i was tryin to tell him once his lens focus to infinity distance, his background blur would not be as pretty etc....
 

Rashkae

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Nov 28, 2005
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#13
thx dd123.

that was 1 point i was tryin to tell another guy...cos the talk was if he has a 50mm, can't he just take lots of steps back to snap a full body shot with bokeh effect.it's a a dx body, so the view is narrower and he need more distance for a full body shot.

i was tryin to tell him once his lens focus to infinity distance, his background blur would not be as pretty etc....
"Pretty" or "not pretty" background blur has nothing to do with focusing on infinity. Not sure why you think there's a link.
 

SkyStrike

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#14
thx dd123.

that was 1 point i was tryin to tell another guy...cos the talk was if he has a 50mm, can't he just take lots of steps back to snap a full body shot with bokeh effect.it's a a dx body, so the view is narrower and he need more distance for a full body shot.

i was tryin to tell him once his lens focus to infinity distance, his background blur would not be as pretty etc....
The bokeh thingy that you are talking about only got to do with the aperture AND the distance of the subject to the background. Got nothing to do with focusing... The larger the distance your subject to the background, the more OOF you will get, the larger the aperture, the more "bokehish" it gets.

Focusing to infinity only means that from x point on wards to the "seeable" infinity everything is sharp. Imo, it's more or less related to hyperfocal distance.
 

ijnek

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#15
hmmm...

pls pardon my ignorance.

with what dd123 mention, when i focus to infinity, there will be no background blur.

every lens has a focusing distance range before it goes to infinity.
 

jsprtan

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May 12, 2010
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#17
hmmm...

pls pardon my ignorance.

with what dd123 mention, when i focus to infinity, there will be no background blur.

every lens has a focusing distance range before it goes to infinity.
This depends on the focal length of the lens, the aperature and also the focus distance. If you get it right you will get half the focus distance till infinity in focus or what is called the hyper-focal distance.
 

ijnek

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#18
thx, i checked that and i'm pretty sure abt focusing distance with related DOF.
i changed the subject distance value to checked the Total Depth of Field.

my concern is every lens has a focusing distance range before it reaches infinity....
 

SkyStrike

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#19
thx, i checked that and i'm pretty sure abt focusing distance with related DOF.
i changed the subject distance value to checked the Total Depth of Field.

my concern is every lens has a focusing distance range before it reaches infinity....
What is this concern that you are concerned about?

So long you know the focal length and the aperture, you can easily know where is the point that it will start focusing to infinity.
 

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