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I'm not getting this DOF (depth of field) thing
I see pictures taken with some lenses and the subject is clear but the background is out of focus. ( Like my 18-200 at short distances.)I have also seen some pictures where everything in the frame is in focus.How is this done? What kind of lens do you use?Sorry for being such an idiot...

Comments (15)

Done by changing the Aperture, small numbers like f/2.8 give a blurred background (called Bokeh), high numbers like f/22 give everything in focus. It is a lot more complicated but that should get you started for now.Benhttp://www.b3nbrooks.com/blog/..

Comment #1

Http://www.luminous-landscape.com/...tutorials/understanding-series/dof.shtmlRegards,Hank.

Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..

Comment #2

Ben Brooks wrote:.

Done by changing the Aperture, small numbers like f/2.8 give ablurred background (called Bokeh), high numbers like f/22 giveeverything in focus. It is a lot more complicated but that should getyou started for now..

You are quite right about aperture numbers, but "blurred backgrounds" are just blurred backgrounds, I'm afraid..

The term 'bokeh' has been imported from Japanese, and refers to the *qualitative nature* of the blur itself..

A lens with "good bokeh" is one that yields out of focus zones with a "smooth and creamy" texture to them....

A lens with "bad bokeh" shows out of focus zones that are "hard and wiry" with distinct remnants of the subject elements still sharp enough to confuse the background somewhat..

Hope this helpsRegards,Baz..

Comment #3

Here is a link to a DOF caclulator. There is also a detailed discussion of DOF which follows the calculator..

Http://www.cambridgeincolour.com/tutorials/DOF-calculator.htm.

Maddog.

Olympus E-510 and a bunch of stuff to hang on it...

Comment #4

DOF depends on focal length and aperture. The shorter the focal length and the more you close the aperture - the more DOF you get..

Http://lordofthelens.co.nz/..

Comment #5

MICHAEL_61 wrote:.

DOF depends on focal length and aperture. The shorter the focallength and the more you close the aperture - the more DOF you get..

{Hmm ... Sorry. That's only half right, Michael. Would you care to guess which half it might be?}Regards,Baz..

Comment #6

Gatedropper wrote:.

I see pictures taken with some lenses and the subject is clear butthe background is out of focus. ( Like my 18-200 at short distances.)I have also seen some pictures where everything in the frame is infocus.How is this done? What kind of lens do you use?Sorry for being such an idiot..

Instead of 'Depth of Field', substitute 'Depth of Focus.' The shorter the focal length, the greater the focus length, or depth. That's why box cameras did not have to be focused. Everything was in focus from three feet to infinity. They had short focal length lenses, with an aperture of f/8. Portrait photographers usually use long focal length lenses, with a wide aperture, so the backgroud is blurred..

Does this help?.

Http://ubereye.deviantart.com/..

Comment #7

Hey guys,.

Care explaining the technique on how to do a bokeh of an object that is 15-20 feet away from you?I am using FZ18 if that helpsthanks..

Comment #8

Misha marinsky3 wrote:.

Gatedropper wrote:.

I see pictures taken with some lenses and the subject is clear butthe background is out of focus. ( Like my 18-200 at short distances.)I have also seen some pictures where everything in the frame is infocus.How is this done? What kind of lens do you use?Sorry for being such an idiot..

Instead of 'Depth of Field', substitute 'Depth of Focus.'.

No. Please do NOT do that!.

"Depth of FIELD", and "Depth of FOCUS", are different things and should not be confused..

Depth of Field occurs in the SCENE in front of the camera, and marks the limits of a zone in-front-of-and-behind the focused subject plane that is also rendered acceptably sharp..

Depth of Focus occurs at the IMAGE plane inside the camera, and marks the degree by which the image sensor can be in-front-of-or-behind the designed plane of focus, and still render an image that is acceptably sharp..

Whilst both kinds of depth are aperture related, please do not suggest that they are interchangeable. Thank you..

Naturally, the distinction between the two was more important back in the days of film, which light sensitive material was not held so flat as a modern sensor, even in the best designed cameras. Glass plates were OK for flatness, and continued to be used well into the era of film when flatness was critical..

Film flatness also became more problematical the larger you got, so Depth of Focus (which can only be used by effectively *stealing* it from Depth of Field) became critical with larger sizes of flat film... A "look down" type shot with 10x8" camera could be completely ruined by gravity pulling down the film into a catenary curve that did NOT stay within Depth of Focus. This was especially true if the drop occurred during the exposure... you got a blurred result, with DOUBLE IMAGING as well!!.

Where large format film is required to approach glass plate levels of flatness, it can be 'sucked back' into position with a device called a "vacuum back". As you may gather, this thing uses an air pump connected to the camera back with rubber tubes..

Http://books.google.com/...ots=qWZxqaeg1D&sig=L63fnW5g-N3KF_Da88EHxFMt48Q.

Anyway.....

Hint: To help remember the difference between Depth of Field and Depth of Focus, just recall that "fields" are TOO BIG to put inside cameras !! .

The shorterthe focal length, the greater the focus length, or depth. That's whybox cameras did not have to be focused. Everything was in focus fromthree feet to infinity. They had short focal length lenses, with anaperture of f/8..

Actually, most box cameras are fitted with lenses close to normal focal length, not particularly short (wide angle)..

The reason they do not need focusing is because they are pre-focused on a special distance called the "Hyperfocal Distance"..

Http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm.

For every aperture there is a separate hyperfocal distance, and it's use extends Depth of Field to the maximum possible..... which typically means from fairly close to the camera (actually, the Hyperfocal distance HALVED) all the way out to infinity..

Once upon a time adjustable camera focusing scales were marked with a red dot, placed at the hyperfocal distance for an aperture of f/12.5 or so, the aperture scale having it's own red dot at the corresponding point. Setting such a camera to the red dots, with an appropriate shutter speed selected, instantly turned an adjustable model into a box camera set up for landscapes and groups in good light.Regards,Baz..

Comment #9

Barrie Davis wrote:.

MICHAEL_61 wrote:.

DOF depends on focal length and aperture. The shorter the focallength and the more you close the aperture - the more DOF you get..

{Hmm ... Sorry. That's only half right, Michael...Regards,Baz.

Barrie,I'm beginner. Could you explain your statement?.

Amadeo..

Comment #10

Noel Wo wrote:.

Hey guys,care explaining the technique on how to do a bokeh of an object thatis 15-20 feet away from you?I am using FZ18 if that helpsthanks.

You cannot "do a bokeh". Bokeh describes the quality of the out of focus areas of the image..

I think what you mean is how do I blur the areas behind the object on which I am focussing..

Answer: to get the maximum blur you want the minimum possible aperture, the maximum possible focal length and an adequate distance between the subject and the background to throw the background out of focus.1. You set the exposure mode to Aperture Priority..

2. You set the aperture to it's minimum value which will be somewhere between 2.8-3.1..

3. You get as far away from the subject as is feasible and still get the composition that you want (this is to maximise the focal length)..

4. If the subject can move, e.g. if it is a person, you get the subject as far away from the background as possible. If it can't move, try to select a viewpoint where the background is as far away as possible..

5. Take a shot and have a look at the results. Try playing around with (3) and (4) as necessary.Chris R..

Comment #11

Amadeo wrote:.

Barrie Davis wrote:.

MICHAEL_61 wrote:.

DOF depends on focal length and aperture. The shorter the focallength and the more you close the aperture - the more DOF you get..

{Hmm ... Sorry. That's only half right, Michael....

Barrie,I'm beginner. Could you explain your statement?.

Yes, of course..

In this posting from up-thread.....

Http://forums.dpreview.com/...forums/read.asp?forum=1002&message=26633702.

..... Hank provides this link to a worthy Luminous Landscape tutorial on Depth of Field .....

Http://www.luminous-landscape.com/...tutorials/understanding-series/dof.shtml.

.... where the following statement ........

"Most people also believe that wide angle lenses have more depth of field than telephoto lenses (false).".

..... is made, and then clarified perfectly well..

[I was hinting that Michael should have read it before making his own assertions, that's all.]Regards,Baz..

Comment #12

Noel Wo wrote:.

Hey guys,care explaining the technique on how to do a bokeh of an object thatis 15-20 feet away from you?I am using FZ18 if that helpsthanks.

The short answer is in the previous response to your post. Longer focal lengths couples with wide open apertures (i.e. small f numbers)..

The long answer is that you may not get the results you're looking for with that camera. The sensor is physically small compared to a full-frame sensor, or 35mm, sensor. There's some optics theory and some math that comes into play, but the result is that it's harder to get strong background blur on cameras with smaller sensors..

Btw I don't know the optics stuff myself, which is why I was unable to explain it  maybe somebody else can if you ask...

Comment #13

It's both correct and incorrect. What I meant - and I think this is relevant to answering the question - is this:.

If you take a picture with, say, 24 mm lens at F 32, it is very likely that in the resulting image everything will be visibly sharp from, say, 1 meter to infinity (I don't remember the exact figures, but that's close enough). On the other hand, if you take a picture with 600 mm lens, no matter how you close the aperture, the resulting picture can't possibly have such DOF. Examples:.

Wideangle DOF -.

Http://lordofthelens.co.nz/JAlbum/Landscape/slides/LIDSKI_LANDSCAPE%20(16).html.

Tele DOF -.

Http://lordofthelens.co.nz/JAlbum/Critters/slides/LIDSKI_CRITTERS%20(6).html.

So, I know exactly what you mean, Barrie, but for practical purposes what I'm saying is also correct..

See more at:.

Http://lordofthelens.co.nz/..

Comment #14

There are some differences based on image sensor pixel density and intended output size. However, more importantly for understanding DOF in general terms, the main factors are the focus distance and the aperture size (actual aperture iris size, not f/ratio)..

Increasing focus distance increases DOF..

Increasing aperture size decreases DOF. Aperture = FL / f/ratio..

In practical use, focus distance is easy to understand..

Aperture works like this..

If you keep the focus distance the same and f/ratio the same, as you increase the FL, the aperture size gets bigger, so DOF decreases. In other words, for constant focus distance and f/ratio, using a longer lens decreases DOF..

Alternatively, if you keep the focus distance constant and FL constant, opening up the aperture (choosing smaller f/ratio value) decreases DOF as the actual aperture opening gets bigger..

If you keep the subject framing the same with different FL lenses by changing the camera to subject/focus distance, as long as you keep the f/ratio the same, DOF will also stay the same as distance changes to offset changes due to the changing FL (which affects the aperture size)..

However, as you can see from this pagehttp://www.luminous-landscape.com/tutorials/dof2.shtml.

Even though DOF remains the same, you can see that the perceived DOF reduces when you use longer lenses as the background items, while not having less detail, are enlarged and give the impression of being more OOF..

Regardless of what a formula might tell you, you shoot for a particular effect, so perceived DOF is just as important as actual DOF, especially when it comes to using longer lenses..

Cheers from John from Adelaide, South AustraliaJohn Harvey Photography http://johnharvey.com.auCanon 40D, Canon 20D & Fuji F10..

Comment #15

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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