what is DOF

[luannf1980]

I see it posted alot? Could someone please tell me what it stands for?
~~annoying newbie~~ lol
~LuAnn~

[PaulEY]

How much of the scene is in focus, it stands for depth of field.

[luannf1980]

Ah thankyou! so so much to learn..this should be fun :)

[Dan-o]

Ah thankyou! so so much to learn..this should be fun :)
Understatement! Hide your credit cards.

[PeaPicker]

This web site may be interesting.
http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html

Welcome to POTN. (Photography on the Net) :)

[donboyfisher]

Whilst it may not be 100% correct, this is the way i envisage depth of field working.

The red lines are the rays of light, and when focused on the object, when they pass through the area between the dotted lines, they are considered in focus. So with a large aperture, the rays have steeper angles and go through the focus band for a shorter distance, thus you get a narrow depth of field.

Stop down the aperture and the angles become much less and the so the depth of field increases.

I also envisage this influencing how blurred the background becomes too....

<< see updated pictures further below in thread >>

[Jon]

Don, that's a very good graphic for DoF. Thanks for posting it.

[Hermeto]

Well, it is not very good but it is acceptable IMHO.

If the blue rectangle represents the subject in focus, DoF should not be distributed equally.
It is about 1/3 in front and 2/3 behind the subject in focus.

[Jon]

Well, it is not very good but it is acceptable IMHO.

If the blue rectangle represents the subject in focus, DoF should not be distributed equally.
It is about 1/3 in front and 2/3 behind the subject in focus. Distribution depends on distance from subject. Close in, it's approximately equal. At infinity, which won't fit on the page with an 800 pixel limit, it approaches 1/3-2/3.

[donboyfisher]

Fair enough, if you do double rays on the front face of the object ( where a ray goes from each corner of the object to the same edge of the lens) , and if i were to take more care about where the lines actually crossed in the middle of the object, then indeed the depth of field is slightly biased towards the rear of the object.

But hey, its was whipped up in Powerpoint, and it illustrates the principles.

*mutter mutter * pedants :D * mutter mutter *

[Hermeto]

Distribution depends on distance from subject. Close in, it's approximately equal. At infinity, which won't fit on the page with an 800 pixel limit, it approaches 1/3-2/3.

Jon, I know how DoF is calculated and distributed and on that account I cannot agree more with your statement.

But I also know that most of newbies are not going to have most of their first photos shots in macro, nor focused to infinity.
They’ll have their first shots most likely focused on subjects say, 10 to 30 feet from the camera.

From this simplified graphic presentation they can get the wrong impression that (in most of their shots) DoF is distributed equally.
That’s all I am trying to say.

[donboyfisher]

That is true, but i wasn't even trying to portray where the distribution of the depth of field would be in relation to the focal object. I was trying to be more basic than that by just showing that the narrower angles simply create a larger DoF.

I've re-done the original so that the lines cross more centrally in the narrower aperture. this has put a bit of a better bias to the DoF.

http://img.photobucket.com/albums/v131/donboyfisher/Camera%20Related/dof02.jpg

Also, the bias specifically called out on this one too :

http://img.photobucket.com/albums/v131/donboyfisher/Camera%20Related/dof01.jpg


I think thats fair enough. Its not meant to be a be-all and end all, just something simple to start someone off with. I followed the link to the Wiki page and just thought it looked a little daunting in places for new people.

[Hermeto]

donboyfisher don’t take me wrong, I am not trying to put down your work.
It is good and I thank you for posting it.

I just thought that it may be even better if you visually present DoF distribution (for most of every day newbie’s shots) a bit better – which you did with your last drawing.
Thanks again!

[nismosr]

This web site may be interesting.
http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html

Welcome to POTN. (Photography on the Net) :)

funny but it took me couple weeks to realize what POTN means, i thought it's one of those photography term. :lol:

[S Taylor]

lol, indeed. If you don't have your POTN setting under control, it can directly affect your wallet. :lol:

[donboyfisher]

POTN is a bit like aperture.

the larger the POTN setting, the smaller the wallet gets.

[StealthLude]

POTN is a bit like aperture.

the larger the POTN setting, the smaller the wallet gets.


lol

ive seen it happen, myself included.