[Mr_red]

Ah – not enough experience to advise.

Chroma key always works for me. I also “Fill” in the motion set-up dialog using set RGB numbers.
But in the Transparency dialog I usually use the eye dropper from a particular point in the scene to find the colour/shade that works the best. Then note the numbers for above.

Chroma is for removing areas of set colour eg putting one object in another background (blue screen)- the others look to alter one colour or grade the original – one application would seem to be the hiding of faces we see in “criminal” videos where the area needs pixelation or dimming. Or we want to “lighten” a face. The provided filters seem to offer these kind of things

I have experimented with the matte box and what I found there, was, that the matte applies to the normal area of the clip, such that if you apply motion the matte will cut parts of the moving image that are not in the “include” area. Wiered – but only because my expectations were different.

[Mr_red]

I haven’t got around to playing with the parameter on chroma key other than “precise” but it looks as if there is scope for a range of colours to be keyed – the problem then is if it pulls-in part of the wanted image and puts holes in the “person/object”

I do mostly still clips at present with chroma key but if it was video I would look at the lighting of the “screen” – shadows from the “object” will make it harder to work with if there is not enough strong light on the screen itself – say from both sides pointing behind the object (off screen of course).

[Mr_red]

do Targa files work? they have alpha channels.

I tend to use stills a lot and it is easy to set-up alpha channel or block filling by editing in Photoshop. I use R=147,G=255,B=183 a lot because it is such a yukky green and provided you force the chroma key to be precise there is not much chance you will find that colour in clothes or even in vegetation – even if you did it would be a very small pixel cluster.

Having said that – Photoshop and Premiere don’t see the colour with the same mix of primaries so using the eye-dropper (in Premiere) to find the colour is essential.

[Mr_red]

So far so good.
Spreadsheet macro can generate the position (etc) values in a usable file.
However the mathematical values make the motion lumpy because Premiere reads only the integer part of any entry/line/field. But is not phased by decimals.

There are lines referring to FracV & FracH & Fracspot so it looks possible. The experiment continues. I will report back here when I have more info.

spot= the posn of the centre

zoom= in %

time= scaled to 1000 = 100%

rot= rotation in degrees

dest= seems to be skew, and entry containing 0’s 80’s and 60’s is probably without any skew.

[Mr_red]

I haven’t got to grips with a matte – can I (say) use it to block-off half the scene with a chroma colour which would be used for keying.

two of these (top and bottom) could then be used on two identical clips to move the clip apart and reveal a bottom layer holding a “second” clip. The motion would be customised.

Can a “blue screen” matte be sized and overlaid to effectivly create an alpha channel.

The only other way I see is creating two clips separately with a chroma fill on each and while they remain in their normal position they result in a seamless join (doubtful) until each move. The upshot then is the end clip is third generation, not to mention the storage they would need.

Slinks away to look at the help file…………… (Assuming it is understood)