Using
Premiere or the standard edition of After Effect.
The goal of this tutorial is to create
a moving object/person that can then be pulled from
the background and placed into another scene. This
is not unlike selecting a part of an image in Photoshop
with the Magic Wand tool and pasting the portion onto
another picture. The difference with video is that
the colour in every frame of your video must be pulled
rather than just a single image. While there are great
plugins, such as Ultimatte to help you complete professional
grade projects, this tutorial will only cover tools
that come standard with your Adobe After Effects or
Adobe Premiere product. In other words, this is for
those who are making their effects on the cheap.
This tutorial assumes that you know
how to start a New Project in Premiere and a New Composition
in After Effects. The Production Bundle is not needed
to complete these instructions.
You will be introduced to the following
concepts and tools:
· Bluescreen
· Alpha Matte
· Masks
For this tutorial miniDV footage
was used and captured using a Firewire/IEEE 1394/iLink
connection. You can still complete this tutorial using
anologue capture, but you are hoping for the greatest
colour consistency and analogue does not always hold
up.
Final Note: Avoid wearing blue
during filming. It will become invisible when compositing.
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Pre-Filming: Things to think about
before filming
· When looking for a bluescreen to film against
there are many options, however, a fabric is best.
It can be draped over odd shaped objects and easily
transported to different locations. If you decide to
use fabric, iron out as many of the wrinkles as possible.
Any hard shadows will be black, not blue, and will
not be keyed out once you apply the bluescreen technique.
· In ideal situations, you
will be able to light your background seperately from
your talent. Unfortunatly, this is not always an option
and extra care must be taken to avoid unintended shadows
directly behind the talent. The above graphic shows
many shadows caused by creases.
· Finally, if you do not have
a bluescreen, or any other coloured screen for that
matter, don't forget that any shot taken on a nice
clear day with a blue sky in the background will do
the trick very nicely.
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Part One: Using Premiere for
quick and simple bluescreen
Once the footage is captured to the
computer, import the video into Premiere and drag it
onto the timeline. Video 2 track or above must be used
to obtain the TRANSPARENCY settings required.
1. Right click on the footage and
choose TRANSPARENCY
2. From the pull down options entitled
KEY TYPE, choose BLUE SCREEN
3. Use the THRESHOLD slider to choose
how strongly the blue is pulled form the video.
4. Use the CUTOFF slider to leave
out areas that may have blue in it, but not as strongly
as the bluescreen itself.
5. If you would like to soften the
edges, choose SMOOTHING and select low or high.
6. Once completed, put any video behind
the bluescreen image and render for visual check.
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Part Two: After Effects, Color
Key, and Masking
Using Premiere for bluescreen is a
good method for some situations, but really falls apart
on others. The problem is that there are bound to be
poor lighting conditions on parts of the image, causing
unwanted artifacts. Also, some parts of the image being
bluescreened are unecessary in the final shot. This
is where After Effects can be used to solve the problem.
Color Key:
1. Import the bluescreen footage and
background footage you would like to use.
2. Drag the bluescreen file to the
timeline
3. Select the Effect option from the
top menu bar and select Keying and finally Color Key
4. This option menu will allow you to choose one of
the shades of blue in the bluescreen in order to remove
the colour. Unfortunately, not all of the blue will
probably be removed and it will be necessary to reapply
the effect and select a different colour blue. For
the example pictured above, three blues needed to be
keyed out.
5. Notice that a blue halo seems to
surround the talent. This can be removed, to a point,
by using the Edge Thin option on the colour that is
closest to the talent. By selecting a positive number,
you slightly choke the matte and as a result remove
the halo, but also shave off part of the talent.
Masks:
The footage is now prepared quite
closely to what Premiere was able to do earlier. However,
the advantage now is that masks can be created to hide
the problem areas that cannot be removed with the Color
Key process.
1. Double click on the bluescreened
footage. A new window will appear that looks like your
original. In fact it is, but you have the ability to
create masks.
2. Choose the Pen tool and click an
area around the problem artifacts. You will notice
that everything else disappears and all that remains
is the artifact.
3. In the example provided, you would
have to change the mask property from Add to Subtract,
as shown above. If you do not see the same menu as
what is depicted, then you simply need to click the
Switches / Modes button at the bottom of the timeline
window, or Right Click on the Source Name title and
choose Panels | Modes to bring up that menu option.
4. Do the same for other problem areas.
What makes these masks even more
powerful is that they are animatable. If desired, a
mask could have been drawn around the talent, only
the above example had very little movement with the
masked off artifacts and animating every time the talent
moved would have taken much longer.
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