![\"Smoke](\"http:\/\/www.premiumbeat.com\/blog\/wp-content\/uploads\/2012\/07\/Header.jpg\")
<\/a><\/p>\nAutodesk has always been known for their keying tools within their visual effects products. \u00a0Simply put, they have some of the best keyers in the business. \u00a0There are 7 keyer node<\/strong>s inside of Smoke\u00a0(Luma, Channel, HLS, RGB, YUV, RGBCMYL, Master Keyer). \u00a0<\/em><\/strong>If you want to include the Modular Keyer<\/strong>, which is a separate node-based keying environment, and the Diamond Keyer<\/strong> inside of the Color Warper<\/a><\/strong>, then you have 9 color keying tools. \u00a0Why so many? Well, Autodesk Flame<\/a><\/strong> is celebrating it’s 20th anniversary, and many of these keyers started then and there. Over time, other keyer\u00a0algorithms\u00a0have come along, each one a little different and a little better then the ones before. And since every keying situation can be different, sometimes one keyer can perform better and give you a better result then another.<\/p>\n [Click on Images for a Larger View]<\/strong><\/em> The Smoke base keyers are the Luma, Channel, HLS, RGB, YUV, and RGMCMYL<\/strong> keyers. The Luma Keyer<\/strong> is a luminance based keyer, generating a matte from luminance levels. \u00a0The others are all color based keyers where you would select a color in the image to key out. In other words, a chroma key. \u00a0Each of these keyers only accept a front image and output a result image which is a hicon matte.<\/p>\n The best chroma keyer inside of Smoke, in terms of features and quality, is the Master Keyer<\/strong>. The Master Keyer also accepts a Front, Back and Matte<\/strong> input and outputs a front and matte result. But we will focus on that keyer in a bit.<\/p>\n Here is an example of how each of the base keyers treat this image when we do a simple 1 click color selection. Images provided by and available via HollywoodCameraWork.us<\/a><\/p>\n Each of these chroma keyers (Channel, RGB, YUV, RGBCHML, HLS)<\/strong><\/em> has a color pot to select the color on the image you would like to key out. \u00a0You then have Tolerance<\/strong> and Softness<\/strong> tools to add\/subtract color information to\u00a0finesse\u00a0the key result. \u00a0You can dial these values using the sliders or by selecting problem areas of the image. \u00a0Depending on the quality of your image, the lighting of your blue\/green screen, shadows, compression, etc, each of these keyers may give a slightly different result. So often it’s good to try them all to see which one works for your given situation.<\/p>\n The Channel Keyer<\/strong> works well when you have a very clean and uniform color channel to key. The other keyers work well when the image has impurities in the chroma key like shadows or creases in the background color.<\/p>\n These nodes just give you the basic key, and result a matte. You would then need to add some other nodes like the Color Curves<\/a><\/strong> for color suppression\u00a0on the edges or Edge Matte Node<\/strong>s to add any shrink or erodes. Perhaps even a 2D Histogram<\/a><\/strong> to clamp the matte and clean up some rough areas, or even a Gmask Node<\/strong> to add a garbage mask to isolate a part of the image. \u00a0And ultimately, comp the front and result key together in Action<\/strong> or in the Blend & Comp Node<\/a> <\/strong>with a background.<\/p>\n The Modular Keyer<\/strong> is the default keyer inside of Action. \u00a0It’s complex enough that it deserves it’s own blog post, so I’ll do no more than introduce it here. \u00a0Basically, it allows you to have a mini-schematic for keying inside of your larger ConnectFX setup.<\/p>\n Your first stop when you have a chroma key to perform, is the Master Keyer<\/strong>. Its name is appropriate as it contains a very powerful and interactive keyer with more tools to generate a clean key than any of the other keyers. By keying with the Master Keyer, you have tools for color supression, correction, and degrain built inside the node. \u00a0There are also Secondary Keyers, called Patches<\/strong>.<\/p>\n Once you have your Front\/Back\/Matte<\/strong> feeding the node, you have a standard color pot for choosing your chroma key color. The Master Keyer has 2 pots so that you can chose slightly different areas, brighter and darker, and then allow you to mix between the 2 to get a good balance for the key overall. Instantly you can see how well the key is working by looking at the matte output (Press F4 twice).<\/p>\n Your key probably isn’t perfect and there might still be some issues to work on. Here is where the Master Keyer excels. \u00a0By holding ALT and clicking in the viewer<\/strong>, will see a Heads Up Display (HUD) that allow you to adjust the key. \u00a0Depending on where you\u00a0click\u00a0in the viewer, you will get different option sliders\u00a0(Matte Overall, Shadow Highlights, Ranges A,B,C,D,E), \u00a0<\/strong><\/em>These are smart sliders, as the Master Keyer is looking at the pixels\u00a0underneath\u00a0and giving you options to fix just those range of pixels. It’s very specific. Adjusting the sliders in context allows you to have real control over the key result.<\/p>\n But sometimes you have a real problem key. \u00a0This is where the Master Keyer’s Patches<\/strong> come into play. Think of them like secondary keyers, similar to secondary color correction in the Color Warper<\/a>. \u00a0Activate the patch by selecting it in the sampling menu. Then perform a Control+Box Selection<\/strong> in the viewer over a particular area you want to clean. \u00a0The Patch will analyse the pixels and assign them as white or black. Obviously it knows from previous selections that if you click to clean up an area that is currently a matte, it will fill in the pixels as white and an area that you want removed, it will make them black.<\/p>\n You have 3 patches<\/strong> to work with, so you can easily clean up areas both inside and outside your matte. \u00a0The range and softness values for the patches are keyframeable. So if you have an area of you key where the lighting changes, and more shadows are introduced, you can adjust the values to compensate as the scene changes.<\/p>\n Once you have the matte looking its best, you can now focus on the edges. Under the Color Menu, You can adjust the\u00a0luminance\u00a0and size of the edge. There is also a color wheel to skew the hue to better match into your background colors. For example, if you were keying your subject over red bricks, you would adjust the luma to match the brightness of the bricks and dial in a bit of red to match. This will help make your composite more realistic by blending the edges. You can also use the viewer interactive approach by selecting Blend from the Sampling Menu.<\/p>\n The Master Keyer will also do color suppression and remove spill on your image. The color is copied from the initial key selection, but\u00a0further\u00a0adjustments can be made in the hue and range. You can choose to turn off the Auto CC<\/strong> as well by deselecting the button. \u00a0You would then need to add a Color Curves Node<\/strong> after the Master Keyer Node<\/strong> to\u00a0suppress\u00a0the color then. \u00a0More than likely, you can just use the internal\u00a0suppression\u00a0in this node.<\/p>\n The output of the node is selectable. The result matte is always sent through the matte output, but the front can be selected to be the result with the background clip, the color corrected front without the back, or you can feed the matte output through the front. This\u00a0flexibility gives you the options to add effects nodes downstream in your schematic and composite the key down the line.<\/p>\n Sometimes while editing you need to get the cuts and timing down of your talent in Chroma Key as they pertain to the script or story. You can use the same keying tools from CFX on the timeline via the AXIS<\/strong> effect…with a few differences. If you place your chroma key talent on V2 with the background on V1 you can add an AXIS timeline effect to the chroma key.<\/p>\n Inside of AXIS<\/strong>, activate the Keyer<\/strong> and you will see a new UI which combines all of the keyers we have talked about thus far, along with color and matte tools, histograms, and Gmasks. All in once neat and friendly package. \u00a0Since all the the keyers are independent, you can test each one and see which one works best for you right in the timeline and you can toggle back and forth.<\/p>\n The color blend and spill\u00a0suppression<\/strong>\u00a0is available with each keyer as well as matte tools<\/strong> for shrink, erode, blur and invert. The histogram<\/strong> can be used to clamp the high and low values to clean up the key even more.<\/p>\n Also, having the Gmask (Garbage Mask)<\/strong> tools at your fingertips makes trimming off bad sections of the scene and highlighting just what you want, can save you time when generating a good key.<\/p>\n Once you have your key the way you like, exit AXIS and return to the timeline. Now, if your scenes are all the same, you can copy the AXIS effect to your other clips, adjusting Gmask as needed. \u00a0If you want to take this into ConnextFX for some more advanced effects, you can do that as well. Select your layers (Chroma Key & Background) add a CFX and make sure ‘Generate Composite’<\/strong>\u00a0is selected. Smoke will then take the effects you have setup already on your timeline and promote them into nodes inside of ConnextFX…with a few issues.<\/p>\n The AXIS effect will become an Action node<\/strong> and the keyer inside will be the same keyer from AXIS. \u00a0The \u00a0keyer in Axis works great in the timeline with 8, 10 and 16 bit clips<\/strong>. But, if you are working with 10 or 16 bit clip<\/strong>s then the keyer in Action will become inaccessible (black K)<\/strong><\/em>.<\/p>\n
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\nThe Modular Keyer<\/strong> inside of Action or in ConnectFX does all of this for you. There are presets for each of these keyers that have the nodes added and linked up. \u00a0You can then add or delete nodes to get the best result for your individual keying situation.<\/p>\n<\/a><\/p>\nSmoke’s Master Keyer Node:<\/h3>\n
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