Green Screen Effects

In this session we looked at how to digitally combine footage taken on green screen on to real locations shot elsewhere. This combined our work with camera equipment, setting up the green screen and finally this.

 We started by importing the footage taken from green screen at 25 fps, and creating a new Composition. Ensuring the transparency of the backdrop is toggled on made this easier. We then cut roughly around the people to get rid of a lot of different shades of green captured by shadows that wouldn't either wise disappear.

 

By then pressing Effects, Keying, Keylight an effect was added that can change various aspects of the image to help it fit in the background. We set the 'screen colour' to the exact green of the screen to get rid of as much as possible. We then set the 'view' to Matte, this turned the image harsh shades of black and white.

The drop down menu's then allowed the whites to be set at bright white, and the blacks at pitch black, getting rid of any grey area. Then we simply changed the softness to give the edge a feathered look that mixes more realistically with the image. The 'screen shrink and grow' option allows you to refine this edge further.

Going to the tab 'Layer', and then selecting 'Pre-compose' and naming this footage as 'keyed' or ''edited' footage will help find layers quicker later. We then dragged the back plate of the city on and moved this layer to where we wanted it to be.

This started to look a lot better, but the colours where still a little off. Firstly we adjusted the levels. to do this we could right click, highlight effect, then colour correction, and finally curves. This works much like Photoshop, simply adjusting the levels to match the back plate. We then added colour correction effect 'Tint' (this allows you to select a white and black from the back plate using the eye dropper to mix the layer in) and we used the colour correction effect 'Exposure' to adjust it further.

Now the transparency can be toggled to off, and we duplicated the keyed layer twice and delete the effects from them.  We then inverted the top layer, and set its channel to 'Alpha.' For the second layer, we set the 'TrkMat' (track mat) to Alpha and added effect channel blur, (under the Blur & Sharpen option) and adjusted this as desired. We then pre-composed these two layers and ensured that the tick box option 'Move all attributes into new composition' was ticked,and named this Spill Alpha.

Next was to duplicate the backplate and name is Spill, move it to the top (in front) of the other layers and set the TrkMat to Alpha. We also set this layers mode to 'Screen' and altered the opacity it to fit. Changing the blurriness will also help this.

The following stage was to add shadows. To do this we duplicated the Keyed Footage layer again, deleted its effects again, and renamed it 'Shadow layer.' This must be directly below the actual Keyed footage layer. We turned this layer completely black by then lowering the Exposure, and then set the Y scale (found on the left hand side on the layer next to the timeline) to -100%, this turned the layer upside-down. We then added Fast Blur effects and lowered the opacity to suit the image. Finally we moved it into position.

Futhermore, we made a new composition called 'Grade' which was only really to alter the Tint and Curves of the image, but could be altered in a separate composition.

The last thing we did was add a Vignette in the Grade Comp. This was basically making a new black solid the same size as the screen, and resenting the mask path to an ellipse shape (just press the circle in the shapes menu.) click this layer to 'inverted' and feather the edge as done previously, and opacity the layer. This adds a subtle, faded, feathered black perimeter to the screen, (a Vignette.)

In conclusion, although this is a time consuming method, it does add a effective alternative to filming in difficult, dangerous and/or impossible locations. I am proud of my final piece, (even though only a second long,) I think it is a worthy first attempt and composting using green screen, and the people look as if they are actually there.