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The Power and the Glory

The Scope of Creative Control in the DI Process

The Power of Power Windows
We have seen how the computer can isolate regions of the picture based on their color or brightness then given special treatment, but there is a whole other way that regions can be isolated, and that is with power windows. Power windows are another type of isolation matte that are simply geometric shapes, such as a circle or a square.  Once the basic shape is selected the colorist can dial in a size and a distortion - the circle can become an ellipse or the square a rectangle. Added to this is an adjustable softness factor that can be dialed in to blur the edges of the power window so the color corrections will blend smoothly into the rest of the frame.

From Left: Original Clip, Power Window for Sky, Enhanced Sky

A rectangle set to the full width of the screen at the top of frame and given a very soft edge becomes a grad filter to enhance the sky, as shown above. This is better done in DI than in camera because you cannot dial in the in-camera effect. Once exposed, you are pre-disposed.  In the DI suite a sky treatment can be balanced from shot to shot regardless of any variations in principle photography. Power windows can also be key framed over the length of the shot for size, shape, and softness so that, for example, a soft ellipse can track with the moving face of an actress as she walks through the scene.

Combining Keys with Power Windows 
Of course, luma keys and chroma keys can be used in combination with power windows to further isolate an area to be affected. A luma key will lock onto everything that is within the range of luminance that it is set for, which means it can pick up objects you don't want. Power windows can present a similar problem since they simply mask off entire regions of the picture and there might be objects that you don't want included in the power window. By working a key together with a power window a very selective matte can be generated. In the example below a luma key is first generated to isolate the entire sky. The power window next to it would obviously also color the tree if it were used alone to add a grad to the sky. However, by combining the luma key and the power window together a sky grad can be added that leaves the foreground tree untouched.

From left: Original Image, Luma Key, Power Window, Luma Key plus Power Window, Sky Grad added

Very Special Operations
The Digital Intermediate process brings to the table much more then just color timing. There are also a number of "special operations" that can be applied to the film that have nothing to do with color. One of these special operations is grain reduction. If a shot (or an entire sequence) appears too grainy the color timed frames can be run through a grain reduction operation to smooth things out to match the surrounding shots. Be gentle here - excessive grain reduction leads to softening the picture. 

Another special process is image sharpening. If a shot is a bit out of focus the frames can be sent though a sharpening kernel to crisp them up. Be careful again - sharpening also kicks up the grain and, if overdone, can lead to an "edgy" video look (Yikes!). And don't think you can degrain a picture until it gets soft then sharpen it back up. The sharpening kernel will just put the grain right back in again. You can't fool mother nature! The truth is that these programs perform their magical effects at the expense of introducing artifacts. The key to success is to use them just enough to improve the picture but to stop before the artifacts become noticeable. 

Deflicker is yet another special operation that might prove useful for your next movie. An errant HMI light, an unnoticed fluorescent light flickering in the background, or some just-out-of-frame helicopter blades are just a few of the possible ways to introduce flicker into a shot. Most DI facilities will have programs available that can remove the flicker and restore your shot to nearly perfect consistency. 

Stabilizing a shot is a truly special operation that you will find in any well equipped DI facility. Perhaps a camera ran amuck and didn't pin register the frames properly. Maybe you did a skip print to speed up a shot but it became too bouncy. Perhaps you forgot to check the shocks on your camera car. The computer has an almost magical ability to convert these bouncing beauties to rock steady with the flick of a switch. Actually, the afflicted frames will have to be run through a sophisticated motion tracking algorithm, but you get the idea. 

Digital paint fixes can solve a wide range of fiddly little production problems and are offered by most DI facilities. The digital paint department can remove the odd wire or boom mike, or perhaps an unwanted corporate logo is visible in frame and needs to be removed. They can also fix scratches, and some facilities even have computer programs that specialize in scratch fixes. Be sure to ask what special operation capabilities your DI facility offers. 

And in Conclusion...
The power of the computer applied to color timing a feature film gives the filmmaker vastly more creative control over the final look of the film than was ever possible with the conventional "wet" process.  The DI process offers an incredibly wide array of color altering tools that are precise and repeatable. It even provides separate creative control over different regions within a frame without interacting or interfering with any other region. It also brings a whole suite of image manipulation tools that can solve almost any film problem from excessive grain to flicker. For a small extra charge, of course.

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With nearly 20 years of experience in CGI and digital effects, Steve Wright is also an international speaker, published author, and widely recognized expert in the digital effects industry.

Steve is an industry veteran with in-depth production experience in digital effects and CGI for feature films and broadcast television commercials, as well as feature film Digital Intermediate. As Technical Director and Senior Compositor for Kodak's Cinesite, he has created digital effects shots for a long list of top Hollywood films. His earlier production experience includes eight years experience as an in-house digital effects producer and  supervisor for CGI studios. He is highly experienced with client interface, storyboard breakdown, production bid preparation, and project management and has extensive technical and artistic experience with digital effects, 3D  computer animation, and even digital ink and paint for cel animation. His production experience includes three years as a 3D animator and 12 years experience of compositing and digital effects. His production projects include over 40 feature films and over 70 broadcast television commercials plus numerous special venue projects. His many feature film credits are listed on IMDb.

To contact Steve or see more of his production background visit his personal web site at www.swdfx.com. Click on the book cover to Amazon.com below to see Steve's very popular book on Digital Compositing.

Related Keywords:digital intermediate, digital negative, film scanning, color timing, film finishing, digital mastering

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