Web Chromakey 2 Manual(7/99)
Contents
1. The resulting image creates the illusion of the commentator standing in the desert itself You can see the results of this editing techniquein varying degrees of success on a daily basis whether you re watching a program that features a virtual studio the T V presenter is transported into a computer generated world actors in a stationary car that appears to be racing down a highway or science fiction films that make Superman appear as if he s actually flying or that depict Star Trek s crew members beaming down to exotic worlds The concept behind this special effect boils down to how well color can be manipulated Although the particular color you use is technically not that important blue is by far the most frequently used color W hy blue Because it s not as frequently found in nature as most other colors Therefore since a bright blue back ground wont compete with most colors on the foreground objects it makes it easier to control whatever it is that you are keying out Chromakey this is how the Chroma Key effect came to be known as blue screening Actual people soon became directors foreground objects of choice soon after the technique was developed because it was fairly easy to shoot footage of actors in front of blue screens and Chroma Key them into different backgrounds human skin features no visible blue pigmentation Even so it s important that you pay close atten tion to the color composition o2. click the left trackball button N ow press Position to define the position of the rectangle with the trackball It s important that the upper left corner is placed precisely where you want it to be since it acts as the anchor for the rectangle the lower right corner moves when you adjust the size while the upper left corner stays put If the toolbar at the bottom of the screen interferes with your adjustments click the arrow buttons on the left and move it to the top of your screen Even if you ve carefully selected the base color that you want to key out you still may get slight color deviations in your image T he color range option allows you to compensate for this deviation by setting a kind of tolerance for the masked color A low tolerance color range number requires a refined uniform color sample whereas a high tolerance number allows for a number of color variations For this tutorial select a color range value of 15 you can always optimize this setting later on This feature designates the general area of your screen that contains the color that will become transparent In most cases the picture range will encompass the entire screen T here may be times however when you want to set a smaller range Let s say for example that you are working with a scene that features mountains a blue sky and a similarly blue colored lake and you want to key out the sky so that it is replaced by stars If you dont set t
3. C asablanca N onlinear digital video editor Chroma Key 2 User M anual ch pendix C roma Key Version 2 Thank you for purchasing Version 2 of the Casablancas C hroma K ey software T his powerful new transition will allow you to create your own blue screen special effects perhaps the most utilized visual effect in both the film and television industries With the help of the Chroma Key you ll be able to plant the Eiffel tower in your garden fill a blue sky with stars and even transport yourself to the top of the Empire State building T he only limits will be those of your own imagination W hat is the C hroma Key The color blue C 2 Chroma Keying is an editing technique that combines two video signals into one by removing unwanted parts from one scene and copying the remaining material over into the other scene The Casablancas specially designed Chroma K ey software takes this concept and incorporates it into atransition that combines two scenes in your storyboard into one visual element Let s say for example that you had video footage of a desert landscape on your storyboard that you wanted to use as your background image followed by a scene of a commentator shot against a blue wall that you wanted to use as your foreground image Once the Chroma K ey transition is applied between the two scenes the Casablanca makes the blue wall transparent and the desert landscape is copied over into the commentator s scene
4. considerable amount of stress upon their spouses or partners if they start painting the living room blue H anging up a simple piece of blue material or a blue sheet also offers anumber of advantages Sheets are easy to remove and they can be easily placed T hey do have their drawbacks however such as the aforementioned folds and wrinkles that tend to produce shadows Light is often the single biggest problen with blue screening T he best blue screen environment can produce shoddy results if the lighting is not suitable First you ll need some strong light sources T he entire blue environment should appear bright and evenly lit when viewed through the camera Furthermore the person and objects shot against the blue screen should also be wall lit some lamps should be focused directly onto the objects T he outlines between objects and the blue screen should be clear and sharp but the shadows from the objects must not fall onto the blue backdrop To avoid this we recom mend a light source shining diagonally from the top The bluescreen room that you ve created probably wont allow for a wide range of camera movements In all likelihood you re probably not going to be able to cover the entire room in blue so you need to keep your camera within the proper range to avoid shooting non blue areas Each camera position including zoom views should be always checked Finally we recommend using a tripod during your shooting session At
5. er to the background track Bkg Combining the C hroma Key with titles In addition to providing exotic backdrops the Chroma K ey can also create titles that feature moving scenery within the characters themselves First find a scene you want to appear within the title C 6 Chromakey itself and record it onto your Casablanca For text that appears to burn for example you could use footage of a fireplace or even an explosion For text that appears to flow video of a waterfall or stream would be ideal Place the scene into the storyboard workbox and enter the titling screen T he title movement mode is irrelevant but you need to avoid using fades rolling titles are no problem Choose a large font and set the color to either blue red or green as long as the color does not appear in the main scene Render the text and make a scene of it Return to the edit window and replace the titled scene in the storyboard it features the green title icon with the newly created title scene in your scene bin N ext place the background scene that contains the fire flowing water etc in front of the title scene in the storyboard N ow place the Chroma Key effect between the two scenes C hoose the color from the title and set the picture range around the text alone the effect can be rendered faster and there will be less errors due to similar colors and render the effect M aking your own blue screen Placement and t
6. f your foreground material Seemingly insignificant details such as the color of someone s eyes could pose a potential problem A Chroma Key tutorial Installing the disk Recording a test scene This brief tutorial will introduce you to the Chroma Key technique You will need 1 A Casablanca system with at least Version 2 of the system software 2 Version 2 of the Chroma Key software 3 A wall sheet screen or other material that s a single color prefer ably bright blue 4 A video camera Insert the Chroma Key software disk into Casablancas disk drive and then turn the Casablanca on Answer all of the questions that appear on the monitor screen as you are walked through the installation process and the Chroma Key effect will then be automatically installed Remove the disk when you re prompted to do so T he system will reboot and you can find the effect within the list of transitions it s called BlueBox First you ll need source video segments for both the background and foreground scenes T he background scene can be video of anything at all although scenery of landscapes tend to work best when you are first learning the technique Selecting the foreground scene however requires more thought T he colors within this scene must be as stable and consistent as possible for it to become transparent If you want to shoot footage specifically for this project try placing someone in front of a blue sheet hung
7. he picture range to only include the sky you ll end up with a starry starry lake that only Van Gogh would be proud of D efining the picture range is similar to masking color the Size and Position buttons are the same The preview button brings up a window that contains a real time preview of your Chroma K ey effect thus giving you a good idea of how your transition will look once it s rendered If you are not happy with the preview or with the final version for that matter you can make corrections using the color range button If you are still seeing parts of the blue wall raise the color range setting If on the other hand you have noticed that parts of the foreground object in our case the person are transparent lower the color range level If the running time is too short the default is one second use the length buttons to make the transition run for two seconds or longer Chromakey C 5 Editing the sound using the 2s and xs buttons Like all transitions the Chroma Key transition can only be as long as the shortest scenes Since your two scenes should be the same length however this shouldn t be an issue Since the Chroma Key effect is a transition the audio from the first scene will be cross faded into the second You can easily remedy that situation however with the help of a few audio editing techniques Once you combine your two storyboard scenes with the Chroma Key effect you can mix y
8. l become transparent once it is keyed out of the scene When you select the mask color button the first frame of the foreground scene appears on your screen along with a digital rectangle which selects the color that will be keyed out you can control both the size and the position of the rectangle by selecting the size and position buttons Please note that you re not selecting the area to be keyed out only the color T he rectangle merely samples a bit of color so the Casablanca will later recognize what needs to be keyed out The more color you can include however the better since a wider rectangle will include any possible variations in the color you want to key out You can make the rectangle as large as you want but only the color can appear within the rectangle not the objects within the scene itself Using our previous example you would want to include as much of the blue sheet as possible within the rectangle but you wouldn t want to include the person standing in front of it If you did then the Casablanca would recognize the colors within the person and later try to key then out as well thus making both the person and the blue sheet transparent Chromakey Color range Picture range Preview button Length button Select Size and define a relatively small rectangle To do this roll the trackball to the upper left corner and the rectangle will shrink in size Once you have reached the size you want
9. our audio so that all sound comes from either the foreground scene If you recall our example of the TV commentator standing in the Chroma K eyed desert you want to hear the commentator s voice in the foreground not the sounds from the background Chroma K eyed in behind her You can also exclusively feature the audio from background scene or employ a combination of the two Before you mix your audio however you need to enter the edit screen and make audio samples from your scenes Select the foreground scene click onto the scene from the list so that the frame around it turns blue and click the Special button O nce you are within the special menu select Scene gt Sample Repeat this for the background scene N ow go into the Audio M ix screen Click on both Chroma K eyed scenes within the storyboard and use the slider bar to reduce the decibel leve for each scenes original audio track O rg until they are muted N ow select the first scene the background scene If you want to hear the sound of the background scene only choose the its audio sample from the list on the left and add this to the commentary track C om in that position T hat s all there is to it You can press Play to check the results If you want to use the foreground scene as your audio source use the foreground sample instead If you want to hear both the background and foreground tracks add one sample to the commentary track and the oth
10. this point we wish you the best and hope you have a lot of fun in creating your first special effects sequences Remember Practice does makes perfect Wed be glad to hear from you about your Chroma Key experiences so that we can develop and improve our product even further Future users will certainly be grateful for the feedback you give us Chromakey
11. up on the wall to use as your foreground scene You re free to use other colors behind your foreground objects but it s best to avoid using black or white for this tutorial well refer to a videotaped scene of a person standing in front of a blue wall Chromakey C 3 Applying the transition M asking a color Cc 4 N ow record both scenes on to your Casablancas hard drive We recommend that you use a high video quality setting T his prevents picture artifacts from occurring which in turn could prove to be rather disturbing on the outlines of your Chroma Key images Trim these scenes down to alength of five seconds each Both scenes foreground and background should be trimmed to the same length for the Chroma K ey effect to work properly N ow place the scenes into your storyboard T he background scene should always appear first to the left followed by the foreground scene to the right Remember T he foreground scene is the one that contains single colored elements like the blue wall while the background scene can feature a number of stationary or moving elements You now have to add the Chroma Key BlueBox transition effect between the background and foreground scene O nce you select the effect you ll see three modification buttons in addition to the standard preview length and render buttons that are available for all transitions Thisishow you select the color within the foreground scene that wil
12. ypss of blue screens To create professional looking Chroma Key special effects you ll likely want to construct an actual blue screen that you can place behind objects and actors W hy blue Well even though other colors tend to work fairly well the color blue has proven to be the most reliable over the last 70 years of filmmaking Classic movies such as 2001 A Space Odyssey Forbidden Planet and Vertigo through Star Wars and TheM atrix have all relied upon the sturdy blue screen effect You can begin to follow in the footsteps of the masters of cinema as soon as you construct your own background Blue screens are usually quite large If you intend to recording station ary actors and small objects a relatively small piece of a material will be sufficient If you plan on having an actor move around a larger area however you ll probably need to cover an entire room with blue material such as the virtual studio we described earlier Finally the room should also be well lit try to avoid daylight since it s the hard to control There are two ways of creating a complete blue screen environment Painting the room wall in blue or covering the walls floor and ceiling with a blue material Chromakey C 7 Lighting Camera placement It s a wrap C 8 Painting is relatively easy and results in a flat texture no messy folds and wrinkles to contend with but many amateur videographers may induce a
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