Introduction to Blender 2.5: Color Grading

Blender 2.5 Lighting and Rendering

Bring your 3D world to life with lighting, compositing, and rendering

• Render spectacular scenes with realistic lighting in any 3D application using interior and exterior lighting techniques
• Give an amazing look to 3D scenes by applying light rigs and shadow effects
• Apply color effects to your scene by changing the World and Lamp color values
• A step-by-step guide with practical examples that help add dimensionality to your scene       

I would like to thank a few people who have made this all possible and I wouldn't be inspired doing this now without their great aid:

To Francois Tarlier (http://www.francois-tarlier.com) for patiently bearing with my questions, for sharing his thoughts on color grading with Blender, and for simply developing things to make these things existent in Blender. A clear example of this would be the addition of the Color Balance Node in Blender 2.5's Node Compositor (which I couldn't live without).

To Matt Ebb (http://mke3.net/) for creating tools to make Blender's Compositor better and for supporting the efforts of making one.

And lastly, to Stu Maschwitz (http://www.prolost.com) for his amazing tips and tricks on color grading.

Now, for some explanation. Color grading is usually defined as the process of altering and/or enhancing the colors of a motion picture or a still image. Traditionally, this happens by altering the subject photo-chemically (color timing) in a laboratory. But with modern tools and techniques, color grading can now be achieved digitally. Software like Apple's Final Cut Pro, Adobe's After Effects, Red Giant Software’s Magic Bullet Looks, etc. Luckily, the latest version of Blender has support for color grading by using a selection and plethora of nodes that will then process our input accordingly. However, I really want to stress here that often, it doesn't matter what tools you use, it all really depends on how crafty and artistic you are, regardless of whatever features your application has.

Normally, color grading could also be related to color correction in some ways, however strictly speaking, color correction deals majorly on a “correctional” aspect (white balancing, temperature changes, etc.) rather than a specific alteration that would otherwise be achieved when applied with color grading.

With color grading, we can turn a motion picture or still image into different types of mood and time of the day, we can fake lens filters and distortions, highlight part of an image via bright spotting, remove red eye effects, denoise an image, add glares, and a lot more.

With all the things mentioned above, they can be grouped into three major categories, namely:

• Color Balancing
• Contrasting
• Stylization
• Material Variation Compensation

With Color Balancing, we are trying to fix tint errors and colorizations that occurred during hardware post-production, something that would happen when recording the data into, say, a camera's memory right after it has been internally processed. Or sometimes, this could also be applied to fix some white balance errors that were overlooked while shooting or recording. These are, however, non-solid rules that aren't followed all the time. We can, however, use color balancing to simply correct the tones of an image or frame such that the human skin will look more natural with respect to the scene it is located at.

Contrasting deals with how subject/s are emphasized with respect to the scene it is located at. It could also refer to vibrance and high dynamic imaging. It could also be just a general method of “popping out” necessary details present in a frame.

Stylization refers to effects that are added on top of the original footage/image after applying color correction, balancing, etc. Some examples would be: dreamy effect, day to night conversion, retro effect, sepia, and many more.

And last but not the least is Material Variation Compensation. Often, as artists, there will come a point in time that after hours and hours of waiting for your renders to finish, you will realize at the last minute that something is just not right with how the materials are set up. If you're on a tight deadline, rerendering the entire sequence or frame is not an option. Thankfully, but not absolute all the time, we can compensate this by using color grading techniques to specifically tell Blender to adjust just a portion of an image that looks wrong and save us a ton of time if we were to rerender again.

However, with the vast topics that Color Grading has, I can only assume that I will only be leading you to the introductory steps to get you started and for you to have a basis for your own experiments.

To have a view of what we could possibly discuss, you can check some of the videos I've done here:

• http://vimeo.com/13262256
• http://vimeo.com/13995077

And to those of you interested with some presets, Francois Tarlier has provided some in this page http://code.google.com/p/ft-projects/downloads/list.

Outlining some of the aspects that we'll go through in Part 1 of this article, here's a list of the things we will be doing:

• Loading Image Files in the Compositor
• Loading Sequence Files in the Compositor
• Loading Movie Files in the Compositor
• Contrasting with Color Curves
• Colorizing with Color Curves
• Color Correcting with Color Curves

And before we start, here are some prerequisites that you should have:

• Latest Blender 2.5 version (grab one from http://www.graphicall.org or from the latest svn updates)
• Movies, Footages, Animations (check http://www.stockfootageforfree.com for free stock footages)
• Still Images
• Intermediate Blender skill level

Initialization

With all the prerequisites met and before we get our hands dirty, there are some things we need to do.

Fire up Blender 2.5 and you'll notice (by default) that Blender starts with a cool splash screen and with it on the upper right hand portion, you can see the Blender version number and the revision number. As much as possible, you would want to have a similar revision number as what we'll be using here, or better yet, a newer one. This will ensure that tools we'll be using are up to date, bug free, and possibly feature-pumped.

Move the mouse over the image to enlarge it.

(Blender 2.5 Initial Startup Screen)

After we have ensured we have the right version (and revision number) of Blender, it's time to set up our scenes and screens accordingly to match our ideal workflow later on.

Before starting any color grading session, make sure you have a clear plan of what you want to achieve and to do with your footages and images. This way you can eliminate the guessing part and save a lot of time in the process.

Next step is to make sure we are in the proper screen for doing color grading. You'll see in the menu bar at the top that we are using the “Default” screen. This is useful for general-purpose Blender workflow like Modeling, Lighting, and Shading setup. To harness Blender's intuitive interface, we'll go ahead and change this screen to something more obvious and useful.

(Screen Selection Menu)

Click the button on the left of the screen selection menu and you'll see a list of screens to choose from. For this purpose, we'll choose “Compositing”. After enabling the screen, you'll notice that Blender's default layout has been changed to something more varied, but not very dramatic.

(Choosing the Compositing Screen)

The Compositing Screen will enable us to work seamlessly with color grading in that, by default, it has everything we need to start our session.

By default, the compositing screen has the Node Editor on top, the UV/Image Editor on the lower left hand side, the 3D View on the lower right hand side. On the far right corner, equaling the same height as these previous three windows, is the Properties Window, and lastly (but not so obvious) is the Timeline Window which is just below the Properties Window as is situated on the far lower right corner of your screen. Since we won't be digging too much on Blender's 3D aspect here, we can go ahead and ignore the lower right view (3D View), or better yet, let's merge the UV/Image Editor to the 3D View such that the UV/Image Editor will encompass mostly the lower half of the screen (as seen below). You could also merge the Properties Window and the Timeline Window such that the only thing present on the far right hand side is the Properties Window.

(Merging the Screen Windows)

(Merged Screens)

(Merged Screens)

Under the Node Editor Window, click on and enable Use Nodes. This will tell Blender that we'll be using the node system in conjunction with the settings we'll be enabling later on.

(Enabling “Use Nodes”)

After clicking on Use Nodes, you'll notice nodes start appearing on the Node Editor Window, namely the Render Layer and Composite nodes. This is one good hint that Blender now recognizes the nodes as part of its rendering process. But that's not enough yet. Looking on the far right window (Properties Window), look for the Shading and Post Processing tabs under Render. If you can't see some parts, just scroll through until you do.

(Locating the Shading and Post Processing Tabs)

Under the Shading tab, disable all check boxes except for Texture. This will ensure that we won't get any funny output later on. It will also eliminate the error debugging process, if we do encounter some.

(Disabling Shading Options)

Next, let's proceed to the Post Processing tab and disable Sequencer. Then let's make sure that Compositing is enabled and checked.

(Disabling Post Processing Options)

Thats it for now, but we'll get back to the Properties Window whenever necessary.

Let's move our attention back to the Node Editor Window above. Same keyboard shortcuts apply here compared to the 3D Viewport. To review, here are the shortcuts we might find helpful while working on the Node Editor Window:

 

Select Node

Right Mouse Button

Confirm

Left Mouse Button

Zoom In

Mouse Wheel Up/CTRL + Mouse Wheel Drag

Zoom Out

Mouse Wheel Down/CTRL + Mouse Wheel Drag

Pan Screen

Middle Mouse Drag

Move Node

G

Box Selection

B

Delete Node

X

Make Links

F

Cut Links

CTRL Left Mouse Button

Hide Node

H

Add Node

SHIFT A

Toggle Full Screen

SHIFT SPACE

Now, let's select the Render Layer Node and delete it. We won't be needing it now since we're not directly working with Blender's internal render layer system yet, since we'll be solely focusing our attention on uploading images and footages for grading work.

Select the Composite Node and move it far right, just to get it out of view for now.

(Deleting the Render Layer Node and Moving the Composite Node)

Loading image files in the compositor

Blender's Node Compositor can upload pretty much any image format you have. Most of the time, you might want only to work with JPG, PNG, TIFF, and EXR file formats. But choose what you prefer, just be aware though of the image format's compression features. For most of my compositing tasks, I commonly use PNG, it being a lossless type of image, meaning, even after processing it a few times, it retains its original quality and doesn't compress which results in odd results, like in a JPG file. However, if you really want to push your compositing project and use data such as z-buffer (depth), etc. you'll be good with EXR, which is one of the best out there, but it creates such huge file sizes depending on the settings you have. Play around and see which one is most comfortable with you.

For ease, we'll load up JPG images for now. With the Node Editor Window active, left click somewhere on an empty space on the left side, imagine placing an imaginative cursor there with the left mouse button. This will tell Blender to place here the node we'll be adding. Next, press SHIFT A. This will bring up the add menu. Choose Input then click on Image.

(Adding an Image Node)

Most often, when you have the Composite Node selected before performing this action, Blender will automatically connect and link the newly added node to the composite node. If not, you can connect the Image Node's image output node to the Composite Node's image input node.

(Image Node Connected to Composite Node)

To load images into the Compositor, simply click on Open on the the Image Node and this will bring up a menu for you to browse on. Once you've chosen the desired image, you can double left click on the image or single click then click on Open. After that is done, you'll notice the Image Node's and the Composite Node's preview changed accordingly.

(Image Loaded in the Compositor)

This image is now ready for compositing work.