Green Screen Composition

Bike Tutorial Finished from Becca Nield on Vimeo.

This is a tutorial which I completed as part of my assignment for Digital Composition which is to be handed in on the 28th of February.

I have included the write up which I wrote as part of the assignment;

The aim of this tutorial was to compose a video in which a green screen is replaced with a background clip. The objectives of this were to demonstrate skills in keying and adding colour correction to the layers to make the final result look more realistic.
In order to get a better understanding of what the effects are doing to the image, research was necessary. The CC Composite effect was used when creating this video, this helps to combine a layer with already has an effect on it together with another layer without that effect on. The CC Composite has different modes like screen and difference, which allow more flexibility in which ways it can be used.
To make this video the follow key steps were used;
• The Keylight effect was added to the green screen footage to start to key in the background footage, within Keylight clip black and clip white were used to get a neater screen matte.
• Then Set Channels, Gaussian Blur, Invert and two CC Composite effects were added to it, this helped to blend the front image with the background image.
• Time Stretch was used on background footage, to reverse it and too speed it up, to match the speed that the actress would actually be travelling at on the bike.
• Luma Key was used to key the whites in the actresses jacket to match the whites in the background, this was added by duplicating the green screen footage layer and adding a mask around the actress, so not to distort the white light coming from the bike.
• The Tint and Hue/ Saturation effects were used with masks to tint the road and the sky different colours, making the road more grey and taking the harsh red tones out of the sky.

The problems that occurred during the making of this composite were; the green screen had black marks on it, which still appeared when you used the Keylight effect. This was solved through painting on the alpha by hand, at some points this had to be done frame by frame to create a green screen key that looked acceptable. Also orange edges occurred around the edge of the frame when the Tint and Hue/ Saturation effects were applied to the sky and the road after experimenting why this was, it was discovered that the mask was cropped to close to the image and the feathering that we added to the mask was causing the orange tones from the original image to seep through.

The final outcome of the project was satisfactory but could have been made better by giving the alpha painting of the black mark for attention by taking longer to go through frame by frame to make sure paint out all of it and the colour saturation of the sky could have been left brighter as it looks pretty faded compared to the original.