Creating Depth of Field
Posted on 10. Nov, 2009 by Andrew Price in Tutorials
Even though we’re creating digital renders in a 3d world, we need to keep in mind that we are still imitating a real world camera lens. Cameras and human eyes have something called ‘Depth of Field‘ (or ‘DoF’), which makes objects in the background and foreground appear blurry.
When used correctly in your artwork, it can draw the attention to the subject and make the scene more aesthetically pleasing. When used wrong, it can seem like another overused tiresome effect. Learn the difference and how to use it effectively.
To play along at home, download this light bulb scene.
The final .blend will be provided at the end of the tutorial.
Let’s get cracking!
Step 1
Open the file and select the camera and press the ‘Show Limits’ button in the edit panel. You will notice that a yellow cross hair appears at the base of your camera.
This is the point that blender will focus on. You can change the position of the cross hair two ways: by changing the DoF Distance value. Or by typing in the name of an object for the camera to focus on. The latter is very useful for animations where you want to change what the camera focuses on in the middle of the animation. I used this technique extensively in my film ‘The Ballad of the M4 Carbine‘, where I made the camera focus on a moving empty that changed moved mid animation.
However because this is only a still we can use the first method.
Step 2
So by clicking the next arrow, make the yellow cross hair sit in line with the exploding light bulb.
With the camera now setup to render, we can move onto the compositor.
Step 3
Switch to the Node Editor by selecting it from the Window Type popup list.
Step 4
Select the compositor icon and the Use Nodes button.
Step 5
Go ahead and disconnect the ‘Render Layer’ from the Composition node.
Step 6
Hit the space bar and add a Defocus Node (Add>Filter>Defocus) and connect to the render layer and composite layer as shown in red here.
Step 7
We want the node to use the data from the cameras Z-depth, so connect the Z input to the render layers Z Output.
Step 8
Go ahead and turn off the No zbuffer and Preview buttons. They are rarely used and seem to exist only so we can turn them off.
Now onto the important part: the fStop value.
Without getting too technical, the fStop value defines how much on either side of the yellow cross hair to make in focus. The smaller you make the fStop value the less of your scene will be in focus. Many artists get carried away by how cool DoF looks, and make this value unnecessarily small. This in turn makes everything appear miniature.
Like this guy.
For an example of how DoF can affect your perception of size, watch this video. It was created using a clever photographers effect called ’tilt shift’ which fakes shallow depth of field.
Step 9
With your understanding of fStop, you should know that light bulbs are fairly small and as a result will need a smaller fStop value. So go ahead and set it to 3.5.
Step 10
Another interesting aspect of DoF that you have control over is bokeh, which defines the shape of the out of focus lights in your scene. Typically old cameras suffered from jagged bokeh but as technology improved the bokeh took on a more circular shape.
So smooth.
However I have found that using a polygonal shape like a hexagon can give a more unique effect. So go ahead and change the bokeh type to Hexagonal and Rotate to 90
The 90 degree rotation simply turns the hexagon on it’s side to make it more obvious.
Step 11
Press Do Composite in the render panel (F10), and hit render!
If you’re a beginner you can stop here as you probably won’t need the next step for your scene, but feel free to read on if you want to get into the tricky stuff.
Using DoF with Multiple Render Layers
You may notice that in the final product, the light filaments of the light bulbs are glowing. To achieve this effect I had to move the filaments to the second layer and make it into a separate render layer.
Glowing node setup
However, when you do this a problem arises: the Z-Depth for the DoF was calculated on the first layer, not the second. Sure, it’d be great if we could just jam two outputs from different render layers into the one hole, but sadly this is not the case.
It's photoshopped. Please don't try this at home.
The ugly truth is: each render layer needs a separate defocus node. Always. However rather than adding it the traditional way and having to adjust the settings on each node to match the other, I have a far more painless way.
Select the original defocus node and hit Ctrl-G.
This will make the single node into a group. Calling it a group is confusing, but if you duplicate it (Shift-D) you will notice that a number appears next to it’s name.
This is the number of users associated with it. Meaning you can make several copies of it and everything in it will mirror the settings of the groups.
Duplicate the group for each render layer in your scene, and compile the layers as you normally would.
Complete node setup
Voila!
Thanks for reading! I hope you now have a better understanding of this often overlooked feature in Blender. If there’s something I’ve missed or anything you’d like me to go into more detail, please let me know in the comment section below!
38 Responses to “Creating Depth of Field”
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13. Nov, 2009
[...] http://www.blenderguru.com/creating-depth-of-field/ a few seconds ago from seesmic [...]
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18. Nov, 2009
[...] guru has posted a great tutorial on creating depth of field using [...]
Charlie D.
10. Nov, 2009
This was a great tutorial. However, the particle system seems to crash every time I try to simulate it. Is there anything I’m missing? I tried adjusting the start and end frames and baking it first but it still crashes. I wish I knew more about the particle system besides fur.
Charlie D.
10. Nov, 2009
I think I figured out the problem. It seems to work find on my laptop which is running Mac OS X 10.4
The computer I was trying to run it off of has 10.5 and I’ve noticed the build for Blender is still a little buggy for that version of Mac OS X
Andrew Price
10. Nov, 2009
Good to hear you got it working Charlie! If you run into anymore problems let me know.
yondertoy
11. Nov, 2009
Hi,
Very nice tutorial, many thanks !
But, did you packed textures images files because it doesn’t appear in the render ? ( ‘PlanksOld0019_L.jpg’ & ‘test.jpg’ )
THX !
Mike
11. Nov, 2009
Haha I want that multi-input node to exist too!
Thanks for sharing, helped me a lot.
Andrew
12. Nov, 2009
Hey yondertoy,
I wasn’t sure if people would want the textures I used, so I didn’t include them.
But obviously people do so I’ve re-uploaded it with the packed textures
Regards,
Andrew
draeath
13. Nov, 2009
Now, couldn’t one use an Add node to merge the render layers BEFORE using the defocus node?
Andrew
13. Nov, 2009
@draeath
Tried that. It merges them fine, but then it’s using the Z-Depth from one layer only, so the DoF for the other layer is maxed out.
I experimented for ages and this was the best solution I found. Also I think I remember pulling apart a source file from Big Buck Bunny and they had used the same method, so I stuck with it.
Husam
13. Nov, 2009
I think you could combine the Z-Depth passes using a Z Combine node. No?!
Regius
13. Nov, 2009
Woohaa! A node tutorial ! I would have done this DOF thing just passing the task to LuxRender, lazy me! Lets dig a little into node editor!
ROUBAL
13. Nov, 2009
Nice tutorial Andrew, as always !
Thank you !
zika
13. Nov, 2009
awsome tutorial, thanks for sharing! I have additional questionis there any tutorial how you create the shattered glass … it looks fantastic!!!
Thank you!
Craigsnedeker
13. Nov, 2009
Great tutorial!
pkblender
13. Nov, 2009
Very clear, well explained.
Thanks!
Benjamin Bailey (Banor)
13. Nov, 2009
Excellent job
yondertoy
13. Nov, 2009
Thanks a lot ! ;o)
Lucas
13. Nov, 2009
Really nice tutorial
. Thanks for good work.
Alexander Blank
13. Nov, 2009
Very concise tutorial…
John Robbins
13. Nov, 2009
This is a great tutorial. I knew how to do the defocus, but was not familiar with the more complex method for multiple render layers. The final product looks great.
What I am curious about is whether there is a way to create a depth field map (luminance-based) that I can render alongside my video or still to load into a program like After Effects. I’m just really digging into 3D and I’m far more familiar with compositing programs. Any help that anyone may have would be greatly appreciated.
-J
Marcus
13. Nov, 2009
@John Robbins: You mean something like a Z depth channel that says After Effects with different grayscale values how far different things were away from the camera?
@Andrew: Is the bulb shattered with explode modifier or manually? Is there a quick way to break meshes up in a random, natural way?
John Robbins
13. Nov, 2009
@Marcus: Yes, that’s exactly it. Then I could load it into the lens blur effect in after effects and edit any look I want in real time.
Any idea on how to render a Z depth channel?
Richard
13. Nov, 2009
Thank you for this. Quick, easy-to-follow, special thanks for the .blend files so I could play along at home.
Jonathan
13. Nov, 2009
THANKS!!!!!!! I was wondering how to do that.
Marcus
14. Nov, 2009
Depth Map Rendering:
http://blenderartists.org/forum/showthread.php?t=80020&highlight=depth
Marcus
14. Nov, 2009
Can you make a tutorial about how the particle system is set up in this scene?
John Robbins
14. Nov, 2009
@ Marcus: Oh sweet. That is awesome. You win the internet.
-J
NeutrinoX
17. Nov, 2009
I have the same crash issue with OSX 10.6
hurm
23. Nov, 2009
Very nice tutorial., thanks, Very clear and usefull
now, one question: How i do to animate the focus on the scene?
thanks
Andrew Price
24. Nov, 2009
To animate the focus simple add an Empty and set the “DoF Obj” value to ‘Empty’ (or whatever it’s name is). Then simple animate the Empty as you normally would.
Eg.
Hit i> select Loc> change frame>move empty to desired position> Hit i again> select Loc (repeat as necessary)
hurm
24. Nov, 2009
Thank you very much, Andrew.
Very clear.
Uakino
25. Nov, 2009
Вот что-то наподобие у меня уже полгода из головы не выходит!
Adam
12. Dec, 2009
Quote:
>To animate the focus simple add an Empty and set
>the “DoF Obj” value to ‘Empty’ (or whatever it’s name is).
>Then simple animate the Empty as you normally would.
>Eg.
>Hit i> select Loc> change frame>move empty to desired
>position> Hit i again> select Loc (repeat as necessary)
Thank you!!!!! Great tutorial; i’ve been looking all over for this!
Hiram
12. Dec, 2009
Adam, if you want animate the focus, beware with the fstop value. because a big value can make focus troubles. this make me headache lol
cheers
devchushka
23. Dec, 2009
Да уж. Как говорится в устоявшемся выражении:
Это мы разрешили немецкие фильмы и запретили грузинские вина…
sdort
31. Dec, 2009
How did you manage to shatter you light bulb??
I got the .blend file, and saw there wasn’t a explode modifier..
Can you tut it?
Deriksims
04. Jan, 2010
Да уж. По поводу коментариев – навеяла на меня где-то услышанная фраза:
Ведь именно мы занимаем бОльшую часть Евразии, чем Евразия не очень довольна.