[Merlin]

I have filmed scenes with camcorder static, not panning , on a tripod, incase this was the best way of then replacing unwanted scenes beyond my subject. The subject is both a static item and also humans moving about in front of it. They overlap the unwanted area at times and are usually this side of the wanted subject. How is this done in Premiere ?...do I need Premiere Pro ?

In the movies they use a blue screen, this was not an option for me, never will be given the size of my subjects !

I imagine that if the foreground subject is also only static, then a mask painted over the unwanted parts could act as an alpha channel and a 'paste inside' be used to kill off the unwanted parts, but what if humans move about over the unwanted parts ?

Merlin

[Mr.D]

There are many ways to seperate images that don't rely on colour difference keying ( bluescreen).

The most basic and unfortunately most manually intensive method is to draw a matte for every frame of the subject you wish to isolate. This is called rotoscoping. Unfortunately you rarely get the edge detail in a roto that you would in a bluescreen key although you can build up the edge detail on a more basic roto by using luma and chroma keys to pick off bits of additional fine edge detail ( hair for example).

If you have a frame without the subject in it or a clear area that the subject later obscures you can also use a difference key although pixel values that are close to the background on the foreground subject will also pick up opacity ( holes) in the matte.

Rotoscoping whilst simple in principle is actually quite difficult and strenuous to do well.
Most digital system are spline based with a linear inbetweening ( auto animating) keyframe system. ( you draw a keyframe on frame 1 and then rekey it at frame 10 and the shape will animate in a linear fashion over the intermediate frames) .There are good ways and bad ways to roto . Sometimes you have no choice but to "keyframe" every single frame as the motion is so variable.

However here are some tips on good roto technique.

Don't start by keying each subsequent frame it defeats the point of having an inbetweening system helping you.

Most rotoscope tools work by allowing you to draw a closed polygon designated by vertices or control points around the subject . Placement of control points on the polygon is important. Don't use too many points ( do not try and roto individual strands of hair for example) and place them on recognisable features where the contour of the subjects changes ( tip of the nose , where the nose joins the lips , tip of the top lip, mouth , tip of bottom lip in the case of a profile for example) When you are happy with the placement of the points then I usually switch the splines to beziers ( softer curves with handles that control the gradients on a lot of packages) Then adjust the curves themselves to align with the contours of your subject ( don't move the points though).

Key the first most complete frame of the subject ( ie if they walk on screen key the first frame that they are entirely visible) then move to the last complete frame of the subject ( ie if they walk off screen key the last complete frame of the subject).

Then either composite or colour correct through the resulting matte a colour ( green is good avoid red if possible as your eyes won't see the edge as well). Don't do it to 100% you still want to see everything in the coloured area not just a flat colour filling the matte. Run a flipbook of the resulting image ( a flipbook is a render into memory rather than out to disc ...if you don't have enough ram in your machine to playback the entire clip then view it in sections and take notes). Note at what frame where the matte deviates most heavily from the subject and adjust at that frame only. Then run a flipbook again and again rekey your matte at the frames of greatest deviation. And continue in this manner until the matte is accurate.

Even if you end up having to key each frame ( which is possible) this method allows the inbetweening to work with you rather than against you ( you will find you have to do less modification to the matte )and it will animate in a more fluid manner and not boil or pop with keyframes fighting each other.

If you feel the matte has too many control points and is difficult to manage and areas are moving differently from others (a full body roto is an example of this) then split the matte into seperate ones for arms legs torso head and deal with each area seperately and then combine the mattes.

( most people with no experience animating : and many substandard animators , will often key at regular intervals until they reach the end of the clip...don't do this it makes life more difficult and disregards what the action of the clip is...this is also a principle of good animation...succesive breaking of points as its called)

As you don't have a bluescreen to work with your only hope is an adequate roto and some additional lumakey work on top really.

[Merlin]

Mr D.
This is most welcoming as a reply, thank you.
I wonder if there is a visual tutorial somewhere on the processes you refer to to assist my understanding of it all, this would enable me to see just what its all about.

I am told that I need Adobe After Effects, though at £567 for standard and £967 for Pro (PC) I shall think twice, or is there another companys program that does something similar for less money.

Thinking ahead...
I would like to be able to add more footage over the top to add vehicles and aircraft to the scene, these again filmed separate, backgrounds removed and sitting on transparent layers prior to being introduced into the current footage.

Envirographics

[Mr.D]

You really need to be thinking about After Effects as a minimum for all that .

I'm not aware of any cheaper decent compositing systems but its always possible there is one out there somewhere. ( Director and Premiere did have some capabilites but its been years since I touched them)

You might be able to get a trial but they usually have a watermark on them.

As for tutorials I don't know about After Effects as its a little low spec for me but Apple's Shake and Discreets Combustion (2) have decent tutorials/manuals that explain some compositing basics as well as the packages.

There are also a couple of books. "The Art and Science of Digital Compositing" by Ron Brinkman ...which really only explains what compositing is ...and "Digital Compositing for Film and Video" by Steve Wright ...which is more useful to a working compositor and probably goblidigook to a beginner.

After Effects is the cheapest I'm aware of ( even cheaper without the production bundle which you really need to do anything to be honest).

Compositing software is quite sophisticated and doesn't sell in huge numbers compared with other packages like photoshop. It tends to be quite expensive ( Shake is $3000 on apple and $5000 on linux) Combustion was similar and then you get into flame/inferno territory which is essentially a hardware system ( way over-rated if you ask me) and costs about $500k upwards.

You can of course find dodgey warez copies all over the place....

You might be able to find an old sgi Octane on ebay with a matador or cineon license on it but you need a lot of experience in unix based workstation enviroments to even get them operational.