Keying In Final Cut Pro HD

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    Keying in Final Cut Pro HD

    By Kevin Monahan

    Chroma keying is a really useful skill to add to your effects creation toolset. Theonly trouble is that it is rather a black art. That is, keys are rarely achieved withprecisely the same settings and it takes skill and practice to do it well. However, ithelps to follow certain basic procedures to be successful at it on a consistentbasis. As long as your image is shot and lit correctly, you're halfway theretowards succeeding at a convincing chroma key effect. This article is written anddesigned for you to achieve predictable results in keying using the Chroma Keyerfilter in Final Cut Pro HD.

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    You can create unique visual effects with the FCP Chroma Keyer. Here, "Linda"

    has been electronically "cut out" and placed on a new background.

    If you weren't already aware, chroma keying is the process of electronically

    "cutting out" a subject shot against a solid colored blue or green screen. Oncethe subject (in our case, a woman named Linda) has been removed from thebackground, you are free to place it on an upper track, say V2. This allows you toplace a different background behind the subject, which opens up newpossibilities for creating visual effects.

    When you are removing the blue or green areas of the backdrop, what you arereally doing is creating an alpha channel, (or matte) which will create an area oftransparency around your subject.

    In this article, I'll be attempting to use the FCP Chroma Keyer on "Linda", which

    is one of the more difficult keying jobs that I have faced in the past few years.This was originally shot on Beta SP with a 3CCD camera that had a pro lens.

    Sounds great, right? Not really. Although the source was of high quality, I foundthat Linda's shiny black outfit absorbed a good deal of spill from a set, which wasstrongly over lit. Also, Linda had 2 quick hand gestures, which made it difficult tomaintain a good solid key for about 24 frames. Because of this, my key will needsome troubleshooting, which will require some techniques that I'll share with youa bit later.

    Let's get started, though, with the process of chroma keying a standard shot and

    I'll work along with you.

    Start with the best possible source material

    Creating a clean key begins before you even launch FCP. As I mentionedearlier, with chroma keying, you'll have to start with the highest possible qualityvideo at the shoot. Perhaps, you have heard the phrase "garbage in=garbage

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    out". This old adage really applies to chroma keying, as a higher quality clip willgive you a smoother edge around your subject.

    Although this article will not instruct you how to shoot for blue or green screen, Ican offer up a few pointers. For more details, read the article by Charles Roberts

    entitled, "Chroma Key Basics for DV Guerillas Part 1". This will give you abroader view on this topic.

    There are a few key points that I can share with you if you have any control overhow the shoot is executed or are actually shooting it yourself.

    Use the highest quality camera and acquisition format possible (Ideally a3CCD video camera). Use larger CCD chips, and quality lenses if possible.You can use miniDV or DVCAM, but your results will be notably improved byshooting with formats such as DVCPro 50, Digital Betacam or HDTV.

    Pay special attention to the lighting. The background should be lit as evenlyand flatly as possible. Strive for no shadows or creases in the backdrop.

    Place your subject as far from the backdrop as possible, so they will not castany shadows onto it. Another reason is so that the backdrop will not create"spill" (reflected green or blue light) onto the subject, making keying moredifficult.

    Light your subject, as you would like to see it in the final composite. Cut offthis affected light from the backdrop with flags or foam core. In my opinion,this is the problem with the "Linda" shot. She was not separately lit apart fromthe backdrop.

    Make sure that your subject isn't wearing clothing or accessories that are thesame color as the background.

    Smooth down any flyaway hair and avoid any fringe in the clothing. Avoidjewelry, like earrings and necklaces that might reflect blue or green or thatmight be difficult to key due to the relative size of the objects.

    Make sure that the talent is not wearing green if you are doing a greenscreen shot or blue if it is a blue screen shot. Black is also not a good choicesince it tends to absorb spill. Note that Linda is wearing an outfit made ofshiny, black material.

    Lock down the camera and do not move it during the shot, unless you knowhow to do motion tracking. Motion tracking is not available in the stock FCPpackage.

    Use a Green Screen is you are shooting video. Use a Blue Screen if you are

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    shooting film or have a blonde haired subject. Either will work, however. Ifyou have a non-human subject, you can use any color for the backdrop. Aproduct shot with blue and green in it might need a different coloredbackdrop, like red.

    Capturing and Editing Considerations

    After the shoot has wrapped and you have the footage in hand, you can begin toprepare it for keying. You'll first need to get it into Final Cut Pro at the bestpossible quality. Most people will probably be using miniDV or DVCAM. This

    used to be problematic because of the limited colourspace of 25 Megabit miniDVor DVCAM (which is sometimes referred to as 4:1:1 sampled footage), but now itis less of a headache with a new filter that was added to FCP 4, called ChromaSmoothing 4:1:1. If you have an opportunity to shoot the piece on a higher qualityformat, then by all means, do so. You'll get smoother edges around your subjectwhen you begin to work on the key.

    A new filter called Chroma Smoothing aids keys shot in 25 and 50 Megabit DVformats.

    After the footage has been logged and captured into a bin, you can beginworking on your chroma key effect. First, place any background footage onto V1in the spot where you wish to start the effect. Then, edit the green screen shotdirectly over the V1 clip on V2. You should turn off the V1 clip temporarily so thatyou can work against the background of the Canvas. To do so, select the clipand type Control + B. In the Canvas, I switch off between the black, white andcheckerboard backgrounds as I adjust a key. These choices are available in theView pop up menu. Leave it set to Black for now.

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    Place the clip to be keyed on V2 and turn off the background layer on V1.

    Tip: Stretch out your Canvas to 100% size as you work. You'll see a moreaccurate representation of your work on your Canvas. Of course, your NTSC orPAL monitor should also be connected to your deck (or video capture card-orbreak out box if working with SD and HD), so that you can see the quality of youredges as you work. After you render and play your composite back, return theCanvas to "Fit to Window".

    Evaluate and then crop or matte your footage

    Scrutinize your footage to see if there are any light stands, boom poles, or other

    anomalies in the shot. After you've evaluated your shots, your next step is to cropor garbage matte out these items at a minimum. I like to matte out as much of thesurrounding blue or green screen around the subject as possible. Why? Youdon't want to spend extra time trying to key out areas of the frame that thesubject will never travel into. It's easier to key a subject this way too as there arefewer shades of green within the matted area. You can even keyframe the cropor garbage matte, if the subject moves around the frame a bit. For this, use asfew keyframes as possible. Step through the frames and make sure your subjectdoes not travel outside the area you've cropped or matted out.

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    Use an 8-Point Garbage Matte to knock out most of the backdrop.To add an 8-Point Garbage Matte to the footage, do the following:

    1. Double click the clip that you want to apply the matte to.2. Click on the Filters tab and then to Effects>Filters>Matte>8-Point GarbageMatte.

    3. Click on the point controls in the Viewer and then click and drag the crosshairs in the Canvas to the point that you wish to matte out.

    4. Continue the process for all 8 points in the matte.5. In this example, I have also turned up the Smooth parameter to 36 to round

    off the edges of the matte.6. Use keyframes if the subject moves out of the matte.a. Place the playhead near the beginning of the clip and set keyframes by

    clicking the Add Keyframe button for each point.

    b. Move the playhead to the end of the clip and reset the points (this will in turnadd new keyframes automatically).c. Move the playhead to the middle of the clip and see if the points need

    resetting.d. Continue the process between any and every keyframe until the subject does

    not step out of the garbage matte throughout the clip.

    Tip: If you do a lot of chroma keying, it helps to have a large monitor or dualdisplay set-up so that you can drag out both the Chroma Keyer and theFilters tab.

    Adding the right Chroma Key filters

    You're now ready to add filters to create the chroma key. You'll need two filtersto get the job done properly: Chroma Smoothing and the Chroma Keyer. Youshould note that there are two flavors of the Chroma Smoothing filter. Use the4:1:1 version if you are working with DV-NTSC. Use the 4:2:2 version if you areworking with 4:2:2 formats, such as, DVCPro 50. It is important to note that youshould apply the Chroma Smoothing filter first.

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    Here are the basic steps for chroma key filter application:

    1. Double click the clip you want to chroma key to load it into the Viewer.2. Click on the Filters tab and then go to Effects>Filters>Key>Color Smoothing

    4:1:1 (or 4:2:2)3. Return to the Effects menu and go to Effects>Filters>Key>Chroma Keyer

    Unfortunately, due to the nature of Pals 4:2:0 color space, you will not use aChroma Smoothing filter at all, as it will do you no good. Currently, there isn't aChroma Smoothing filter for PAL users that I am aware of.

    Pay close attention to stacking up the filters in the proper order

    Tip: If you are using a Garbage Matte, it must lie below the Chroma Keyer filterin the Filters tab stacking order.

    What is Color Smoothing?

    The Color Smoothing filter "pre-blurs" the blue channel in the image just slightlyand only horizontally. The reason that you'll want this pre-blurring in your imageis that it will smooth out most of the "jagged edges" around your chroma-keyedsubject. Gone are the rough edges that you've seen when using DV-NTSC assource for chroma key effects in the past.

    If you still use FCP 3, there is a color-smoothing filter available. Download a filtercalled H. Chroma Blur and another called Chroma Offset (Y/C Delay) from AdamWilt. Got to: www.adamwilt.com/SteppyEdges.html. Even if you do have FCPHD, you may find them useful for certain situations. Check out Adam's site for thefull scoop on how to use these filters.

    G Filters' "G Nicer" from www.nattress.com is also an excellent chroma-smoothing filter.

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    Primary Keying

    The goal of primary keying is to knock out most of the background using theChroma Keyer filter. The Chroma Keyer has two primary interfaces: the visual

    and the numeric interface. They both work the same way, however, it is a goodidea to start in the visual interface to use the Select Color Eyedropper, which isnot available in the numeric interface.

    You can easily switch back and forth between interfaces once you get movingon the matte, however. Here's how:

    1. From the visual interface, you can get at the numeric interface by going intothe Filters tab or by clicking on the button that says, "Numeric".

    2. If you are in the numeric interface, you can go to the visual interface byclicking on the button that says "Visual" or by clicking on the Chroma Keyer

    tab.

    Now that the proper filters are applied in the proper order, you can go aboutremoving most of the blue or green background. For this, you'll use the SelectColor Eyedropper.

    The Controls of the FCP Chroma Keyer

    Use the following technique to knock out most of the background:

    1. Click on the Select Color Eyedropper and then click on a portion ofblue or green screen near the subject. A good portion of the background color

    should fall away.

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    Click on a green area near the subject with the Select Color Eyedropper

    1. Click on the Select Color Eyedropper once more and then hold the Shift keydown. Return to the Canvas and click on a remaining chunk of blue or green.

    It helps to zoom into the image to Shift + select smaller patches of green or blue.

    1. Continue this process until most of the blue or green is knocked out. Youmay want to zoom into the Canvas to select the smaller areas of green orblue with the Eyedropper. It's OK to leave some of the blue or green aroundthe subject for your edge detail. More on that in a minute.

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    Continue to shift + click on patches of green or blue with the Select ColorEyedropper until most of the background color is gone.

    Fine-Tuning the matte

    Once the basic matte is created, you can then work on fine-tuning the edge

    detail of the matte, which is where the real art of keying takes place. Since amatte is defined by the colors black and white in the alpha channel. You'll getstarted on this process by knocking out the remaining blue or green patchesaround the subject and any blue or green "halo" around the subject.

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    A matte is defined by the colors black and white

    Monitoring the matte

    To do get your matte looking good, you'll be finely adjusting the controls of theColor Control Strip, Saturation Control Strip and the Luma Control Strip. Beforeyou start fine-tuning though, it is helpful to know how to see the matte as youadjust it.

    I suggest that you drag out the tabs of both the visual interface and the numericsettings at the same time as you work. That way, you'll be able to manipulate

    either set of controls subtly as you check the matte. Perhaps you can see whyhaving a lot of screen real estate is very beneficial when creating video effects!

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    Manipulate the controls from either interface to finely adjust the matte. I alwaysuse both interfaces.

    As you adjust the controls, you'll be constantly switching back and forth to theaffected image (against black, checkerboard or white) and to the black and whiteimage of the matte. Check the image after each adjustment of the controls to seethe progress of the matte. It's important to monitor the matte to see whether youare improving the matte or destroying it. You are improving the matte when it isdefining the shape around your subject. You are destroying it when the matte isdissipating around your subject. If you see areas of gray within the main part ofthe matte, then you are also destroying it.

    I use the Source/Matte/Final button (it's the one with the key on it) to switch backand forth quickly when monitoring either the matte or the final image. To engage

    each mode, just click on the button.

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    The Source/Matte/Final Button is for switching between modes. Check yourmatte frequently as you fine-tune it.

    Red Key: You are monitoring the affected image in its final state. Here, youare checking the image against the Canvas (black, white or checkerboard) or

    the intended background. Black Key: You are monitoring the matte. In this case you are checking forthe quality of the matte. Black denotes 100% transparency, white shows as100% opacity and gray areas illustrate the semi-transparent areas of thematte.

    Blue Key: You are monitoring the source image. In other words, you are notseeing any effect at all. This mode is nice to have when you need a referencefor color correction time (keying can slightly affect the colors in your subject).

    How to fine-tune the matte

    You'll need to complete the following steps to fine-tune the matte created by thechroma key. Your goal here is to minimize any green or blue around the edges ofyour subject.

    1. Evaluate the problematic areas of the base matte. See if there are any otherspots besides a slight ring or "halo" around your subject. If there are largechunks of color remaining in certain areas around your subject - you maywant to shift + click on the area with the Select Color eyedropper or furthercrop or matte them out.

    2. Next, you'll make small adjustments with the parameters of the Color, Lumaand Saturation control strips. At this stage, I usually widen out the controls ofeach control strip just a bit. Work on the Color control strip first:

    a. Click and drag a handle at the top of the Color control strip to the left or rightjust a bit. Both handles should move in unison. This allows a few moreshades of green (or blue) to be included in the selection.

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    Adjust the controls in the Chroma Strip first.

    b. Click and drag either one of the bottom handles a bit to the right - they should

    both move simultaneously. This makes the tolerance softer so that the othershades of green will gradually be introduced to the matte.

    c. Click on the Source/Matte/Final button twice and take a look at the matte. It'sOK if it is not perfectly defined just yet. It's going to take a bit more work withthe Saturation and Luma controls.

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    1. Repeat the process you went through in Step 2 for the Saturation controlstrip and Luma control strips (note that top handles now work independently).This time around, make much smaller adjustments with each handle.

    2. Continue to flip back and forth to the matte using the Source/Matte/Final

    button to see the results of each adjustment. I tend to move the top handlesoutward toward white or black just a bit while stretching out the bottom onesquite a bit more. You'll know when you are in the zone by continuallychecking the matte. Remember that when checking the matte, it should beblack (indicating transparency) around the subject and white (indicatingopacity) within the subject. Your job is to eliminate all of the gray areas insidethe matte.

    Work to eliminate all of the gray areas within the matte, as shown.

    1. Check your keyed subject against the black, white and checkerboardbackgrounds. That way you can more easily detect if there are any remainingareas of the background that have not yet been removed. You can changethe Canvas' background in the View pop up menu.

    2. Continue to adjust the controls until only a very slight rim of the green or bluebackground is shown around the subject. Recall that you can tweak thecontrols in the numeric interface, as well, to make more slight adjustments tothe matte.

    Tip: In both interfaces, you can use "gear down" behavior to make slightadjustments with the sliders for your key effect. Do this by holding down theCommand key as you click and drag.

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    Continue adjusting the controls of the Color, Luma and Saturation strips until you

    remove most of the green around the subject, as shown (image zoomed to200% for emphasis). A bit of green or blue around the edges of the subject isOK at this point.

    Preserving edge detail in the matte

    With the FCP Chroma Keyer, it's not too difficult to get a key working to about95% effectiveness. That is, when inspecting your matte it is either black or white.That's great for a start, but at times, you need to bring out the grayscale areas ofyour matte to preserve the detail of certain items, such as clothing fringe, hairand smoke. These have to appear as semi-transparent in the comp, so they arerepresented by grayscale values in the matte.

    I find that adjusting the Softness sliders for all three-control strips are mosthelpful for getting grayscale values back into your matte, especially the Key onLuminance controls. The Softness sliders are akin to the visual interface's drag

    handles located at the bottom of each control strip.

    Tip: It is sometimes helpful to switch off one of the enable buttons for the Sat orLuma control strips when fine-tuning the edges of the matte.Adjusting the matte's edges

    Great! So far, you've gotten a lion's share of the work done by shaping the mattewith the controls. The next few steps will be primarily concerned with fine-tuning

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    the edge of the matte, while preserving as much edge detail as possible.

    At this stage of the game, there is a trade off between thinning your matte andpreserving fine detail. At this point, hopefully you only need to adjust edgethinning and edge softness very slightly. If there is spill (color from the backdrop)

    in your effect after the keying is done, you can tame it with the Enhance slider.

    How to use the Edge Controls

    Locate the Edge Controls. They're at the bottom of the Chroma Keyer's visualand numeric interfaces. Here's the way the Matte Edge controls work:

    Edge Thin is will "choke" the matte. That is, that it will either expand orcontract the selected area defined by the matte. Pushing the slider to the leftwill expand the matte and to the right will contract the matte.

    Softening will smooth the edges of the matte. This helps with blending the

    subject with the background. Enhance should be used if there is spill lingering in the edges of the matte.The Enhance slider is used for spill suppression. Recall that "spill" is colorfrom the backdrop lingering in the key effect due to grayscale areas of thematte.

    How to adjust the edges of the Matte

    To adjust the matte's edges do the following:

    1. Click and drag the Edge Thin slider to the right until you see little or no greenaround the edge of your subject. This shrinks the matte a bit. Go lightly as tonot destroy the edge detail of things like fingers, noses and hair. Hopefully,you can see the fringe is much thinner.

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    the area around Linda's hand is still giving me some trouble. This is becauseher hand is in motion, creating some gray in the matte.

    1. Click the far right arrow once or twice on the right side of the Softeningslider. Don't overdo it on the Softening. A setting of 1 or 2 should be fine.

    Too much Softening will give your subject a halo effect, and you usuallydon't want that.

    A setting of 1 or 2 for Softening will improve the key effect. This allows for betterblending with the background. There is still a touch of green in betweenLinda's fingers, so some troubleshooting may be required for this area of thematte.

    Take a look at the matte to see how softening has affected the edges.

    1. Your chroma key effect should now be complete. Click on theSource/Matte/Final button to show the final result of the key. Turn thebackground clip back on and step through the composited shot. Evaluate the

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    effect's edges against the background and make any adjustments ifnecessary. Hopefully, you've done better than I have. I've found that it isdifficult to maintain a solid matte when Linda moves her hand rapidly up topoint to the top of the screen. I'll need to do some troubleshooting on thematte, which I'll cover in a bit.

    Step through the shot to see how the key is working and to do a final checkon the edges.

    Finishing Touches

    Congratulations, you've just completed the process of keying your subject fromthe background. You should see your subject completely separated from thecolored backdrop. There are now a few details you can take care of to improvethe subject and background.

    You can add filters to the footage so that the subject and background matcheach other more naturally. I usually reach for the Color Corrector 3-Way andGaussian Blur filters to get the job done. After all the layers are in place, makesure that everything blends together well. It is no accident that I chose to tint thebackground a green color. Tinting the background the same color as the green orblue backdrop is one way to hide problems with a poorly defined matte.

    Color Correction

    Chroma keying often alters certain color values, so it's a good idea to do a colorcorrection pass to your subject (and/or your background). Typically, I will add aColor Corrector 3-Way to each clip [so as] to not only improve image fidelity, but

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    also to look toward makings making the color and brightness values more evenlymatch each other.

    Here, I've color corrected the "Linda" shot by applying a Color Corrector 3-Way filter.

    Blurring for Perspective

    You may want to blur the background slightly to give the composite the illusionof depth. To do this:

    1. Double click on the V1 clip2. Go to Effects>Video Filters>Gaussian Blur to add the filter to the clip.3. Click on the Filters tab to adjust the slider for the blur. Of course there's lots

    of different ways to blur the background. You might want to look into 3rdparty plug-ins for even more options in blurring.

    Here, you see the tinted the clip, to which I added a Gaussian blur filter. Afterblurring the clip a bit, I then offset the clip's wireframe (Note: place the wireframeon the X, Y axis using whole, even numbers in the Motion Tab). My intention is tomake a "video wall" effect to play behind Linda.

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    A bit of blur added to the background makes for a more convincing composite.I've also offset the layer to appear as a "video wall".

    Bringing the Composite Together

    Now that both major elements have been color corrected, and the background isblurred a bit, you can put together the composition. In this example, we'll make asimple comp featuring Linda on a virtual stage introducing some flying bulletpoints.

    In the following figures, I've built a simple virtual set for Linda. After colorcorrecting, blurring and positioning the background, I can start placing theelements for the comp around the Canvas. I'll first fashion a "floor" and then bringLinda into the shot.

    For the floor of the set, I just distorted and rotated a simple Color Matte andplaced it on a lower layer so it appears behind the background layer.

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    I've added a "floor" made up of a distorted and rotated color matte and placed itbehind the background.

    Leaving the left side black, and lining up the rest of the edges, I've fashioned asimple "virtual set" for Linda.

    When you are putting together a composite featuring a keyed subject, keep in

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    mind that you can rotate, scale or position it anywhere you like on the Canvas.You can even duplicate the clip on another video track to have multiple copies ofthe subject in the frame at the same time.

    Here, I've offset Linda to the right of the composite. This will allow space to placethe incoming bullet points.

    Duplicate a keyed clip on another video track for multiple copies of your subject.I've also added the Perspective>Flop filter to the clip on the left.

    At this point in time, it's a good idea to bring your subject into the comp and doany final adjustment to the key, color correcting or placement of the image.Remember to check your clip in the Motion Tab to adjust placement with theCenter (again, rounding off the X, Y integers to whole, even numbers) and scale

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    parameters.

    Test your subject against the background and make any final adjustments to thekey, color correction, placement and scale.

    Add another color matte with a Matte>Shape Mask>Rounded Rectangle and 4layers of text using Title 3D on top of that to complete the composite as seenbelow.

    Once again, here is the final result of the combined layers.

    Troubleshooting a bad key

    Keying is certain to test the limits of your patience, particularly when things are

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    going wrong. Note my case of Linda and the difficulty of maintaining a matteduring quick hand movements. Here are some potential pitfalls that may happento you, and some ways to solve them.

    The source imagery is poor

    This problem can run the gamut, but is typically related to poor pre-productionplanning. I find the most common problems are that the background is unevenlylit or there are creases and folds in the material that makes up the backdrop.

    For these kinds of issues, all you can do is crop or garbage matte out most ofthe problematic areas around the onstage area for the subject right inside FCP.Hopefully, by tweaking the Chroma Keyer's controls lightly, you can often find azone where the unevenly lit backdrop or creases in the backdrop will disappear.If you have a backdrop that is very unevenly lit, see the next section.

    Matte Problems

    If your backdrop is really unevenly lit, or if you have rapid movement within yourclip (as with Linda's hand), then you may have trouble with keying your subjectthroughout the length of the clip. The problem centers on having to select toowide tolerance for Chroma, Luma and Saturation, making it difficult to create aclean key (or alpha channel) for both the main subject and the problematic areasof the matte. As you already know, when too much gray gets introduced into thealpha channel, it ruins it.

    The only way to get around this problem is to stack the identical copies of theclip and garbage matte (or crop) out the two most wildly different lit areas of theclip. Then, apply a separate chroma key filter to each layer. You can now haveseparate, more accurate filter settings for each area.

    This is the technique I would use for the problem we had with Linda's fastmoving hand. The rest of the key looks fine, so I just cut out the hand and a smallpiece of her arm on one layer and the rest of her on a lower layer. Disarmingimage, isn't it?

    After separately keying each layer, I was able to get better results. As you cansee, the final result in blending these two layers is seamless. You may find itinteresting that many green screen composites are made up of more than a fewlayers with a different Chroma Keyer filter applied to each layer.

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    The problematic hand has now been isolated with a 4 Point Garbage Matte andhas its own Chroma Keyer filter.

    An 8 Point Garbage Matte isolates everything but the arm for the Chroma Keyon the lower video track.

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    When the two clips on both video tracks are rendered and playing back, theblend is seamless. Although I was not completely successful in fixing the key forthe hand, it will be acceptable for the short amount of time that Linda moves it.The tinted background will also hide anomalies.

    You are still seeing fringe around the key

    It's quite common that after you've gone though the above steps, you still havetrouble with the edge showing a little of the colored background, as was the casewith the shot of Linda. If this is the case, you can continue to adjust the ChromaKeyer's controls (or reset them and work from scratch), you can also try adding aMatte Choker filter. Here's how to work with the Matte Choker:

    Note that the Matte Choker should lie at the bottom of the filter stack, but in frontof a color corrector filter.

    1. Double click on the clip. Place the playhead on the clip as you work.2. Go to Effects>Video Filters>Matte>Matte Choker3. Take Softening slider to Zero in the original Chroma Keyer.4. Take Edge Feather to Zero in the Matte Choker filter.5. Adjust the Edge Thin slider in the Matte Choker until the background fringe

    is gone.6. Add a few clicks of the right arrow on the Edge Feather slider in the Matte

    Choker.

    It is unnecessary to readjust the Edge Feather slider in the Chroma Keyer.

    Color Correcting a composited key

    If you needed to have 2, 3 or more layers making up your chroma key effect (forexample, if you had an unevenly lit background), and a color correction isneeded, then I suggest that you nest them first and then add the color correctorto the nest. As I mentioned, the goal of color correcting your keyed shot is tomake the subject look as if really belongs into the background to provide a moreconvincing composite.

    Here's how:

    1. Select the clips2. Type Option + C to collapse the images into the nest. Name the nest and

    Click OK in the Nested Items dialog box.3. Apply the Color Corrector 3-Way to the nest. Select the nest and then go to

    Effects>Filters>Color Correction>Color Corrector 3-Way4. Option + double click on the nest to work on the controls for the Color

    Corrector 3-Way in the Filters tab. That way, you can reach the color

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    correction effect you desire.

    Using Other Filters and 3rd Party Solutions

    Let's say that you've tried the methods that we've already discussed and you're

    still getting nowhere with your key, it's possible that the FCP Chroma Keyer andChroma Smoothing filters just aren't doing a satisfactory job. In that case, youcan try out some of FCP's legacy key filters, such as the Blue and Green Screenfilter or the Color Key filter, but I cannot recommend them. The Spill Suppressionfilter can be useful for excessive spill on the interior area of the matte. as theEnhance slider only works on spill around the edges. Just make sure it lies belowthe Chroma Keyer and above any Color Corrector you may have.

    If you have some extra bucks tucked away for FCP plug-ins, there are somevery good ones out there. 3rd party plug-ins usually have more controls for bothenhancing and repairing chroma key effects. DVMatte Pro is the new kid on the

    block, but it is one of the better keyers available for FCP. It is conveniently laidout and fairly easy to use. You just start at the top of the filter and workdownward. It essentially takes two color difference keys, one based solely onLuma making it very effective. I like the color matching tools and light wrapfunctions, as well. The filter ships with plenty of instructions including QuickTimemovies.

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    DVMatte Pro is one of the better 3rd party keyers for Final Cut Pro HD

    Here, I've used DVMatte Pro on the Linda shot and even though I am a novicewith the plug-in, I was able to get her hand keyed out fairly easily and withouthaving to resort to any of the troubleshooting techniques I've already discussed.Chalk that one up to the helpful tutorial material that comes with DVMatte Pro.

    Boris Continuum Complete has a number of filters that are very useful forkeying. Their Chroma Keyer has its preset controls set for knocking out about90% of any key, so it gets you "in the zone" right away. There is also a 2 wayKeyer for when your talent shows up in a shirt that is nearly the same color asthe blue screen. There are also a number of matte repair oriented filters, as well.

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    Of the two, I would say that DVMatte Pro has the more powerful keyer, but it'snice to have the matte repair filters in BCC. You never know when you may needthem.

    At press time, I should mention that the new program from Apple called Motion

    will be shipping with a copy of PrimatteRT by Photron. This is a high quality 3rdparty keyer built right inside of Motion. That means you can jump in and out ofFCP easily with the newly keyed effect courtesy of PrimatteRT's advancedtoolset.

    FCP Keying Conclusions

    I have found that if you've got good source footage and a bit of patience in

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    creating the matte, the Final Cut Pro Chroma Keyer works fairly well. Theaddition of a Color Smoothing filter adds to its effectiveness. Do a bit of colorcorrection to enhance the look of the chroma key effect, as well. If your footagehas a lot of problems, look into the possibility of purchasing a 3rd party keyer, or

    Apple Motion. It's nice to have a back up keyer anyway, if you need to do a lot of

    chroma keying.

    By now, you should have the basics of chroma keying under your belt. I hopeyou have enjoyed this article. Good luck to you in creating great video effectswith Final Cut Pro and may all your keys be clean!

    Kevin Monahan is a film and video specialist and has been working professionally in radio,television and film for 15 years. He has recently written a book entitled, "Motion Graphics andEffects in Final Cut Pro". He is also an Apple Certified instructor for Final Cut Pro and Motion andteaches both privately and at the Bay Area Video Coalition (BAVC) in San Francisco, CA. Kevinco-founded the SF Cutters, the world's first Final Cut Pro User Group and runs the website

    www.fcpworld.com. For bookings or more information, contact Kevin by email at: Kevin Monahan([email protected].)

    copyright www.kenstone.net 2004

    2000 -2004 Apple Computer, Inc. All rights reserved. Apple, the Apple logo, Final Cut Pro,Macintosh and Power Macare either registered trademarks or trademarks of Apple. Other company and product namesmay be trademarks of their respective owners.

    All screen captures, images, and textual references are the property and trademark of theircreators/owners/publishers.

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