Visual FX

Compositing

As I have mentioned, it is extremely difficult to get permissions from production companies to allow me to demonstrate different techniques. So the easiest (?) thing was to create my own images and correct them to demonstrate what can be achieved with a little thought and a little bit of extra work (for me). It is pretty easy to see how a grade is achieved. It is not always so easy to see how something is created from scratch. As a bit of fun, myself and my quintuplets got together to watch a film at the local flea pit, or have we? What a handsome group we are.

Many images are a composite from many different images and elements to create a two dimensional flat image that hopefully works, or 3D. As we know dodgy effects shots can certainly ruin a sequence and I'm sure we can all name loads. Something to bare in mind is that when creating images from film or another medium they may have come from many different sources and therefore will all need to be treated differently and have their own specific lighting/colour characteristics. This makes compositing extremely challenging and I believe a true art form. However that said if the raw material is poor the final composite is most likely to be poor.

When a final project is transferred to DVD or another medium, it is useful to note sometimes composites that worked so well for a film production invariably look wrong on your TV at home. Conversion processes and low bit rates can cause problems, as can grading across the composite because it will change the black levels slightly. When you adjust the blacks across an entire scene, an edge around the composite may become slightly darker than the rest. It is something that cannot be fixed in a grading session, not easily anyway.

I hate to admit but sometimes a harsh grading correction will separate a good compositor from a bad one. Although I should not entirely blame the creative, some manufacturers can be to blame too. The tools they may be using may sometimes use a lower than beneficial bit depth across a key or matte, introducing banding or artefacts. That composite may look perfect on an 8 bit monitor the creative may be working on, so not necessarily his or her fault. A lot of these problems are not a problem on most projects anymore because the equipment is now powerful enough. Nothing less than 10 bit log or 16 bit linear images will be used, so these anomalies do not occur as often.

 

'Quintuplets' - Final Composition, basic compositing with final grading technique.

 

The composite was created using my basic home digital camera, a Nikon 8400, which photographed all of the images for the composite. As a matter of interest and for my own interest I did not white balance the image at source. Therefore the final images for compositing had a tungsten imbalance giving an orange hue. I knew the shot was going to look like a film was playing, therefore a subtle day to night grade.

Secondly there were two passes of imagery recorded. This was to check all of the detail between the two passes and to give me more flexibility during the compositing stage. The BG image chosen had the projector illuminated in the background, which also made the seating and foreground a lot lighter than the background. You will notice there is a vast difference in contrast between the illuminated pass (projector running) and the second pass across the seating.

 

 

For the final composite the background was composited along the radiator edge to give a slight lighting edge across the top of the shelf over the radiator blending down into the darkness. Also the other version created a shadow from the stop cock of the radiator that would not have been there. The foreground seats were used because I felt they would be better during the grade because in the gloom of the theatre there may be more detail. When a compositor undertakes a project they have no idea what is going to happen to the final composite after they have finished. One thing I have witnessed which I believe is completely the wrong way of working, the compositor sometimes slightly corrects the BG plate. Therefore when it is cut back into the sequence it no longer matches the original shots - of course the composite looks lovely in isolation but the shot now looks out of place within the edited sequence, especially if another compositor works on another scene and does not give the same correction to the BG plate. It happens and can be very noticeable. As a rule of thumb, never colour correct the background plate as it may not match the scene either side from which it was taken.

 

Final composite - without grading, specular bloom or grain added.

 

Many FX shots within a scene are built from hundreds of different layers and elements. It is amazing how much detail goes into an effect to make something work. For period dramas, many modern day conveniences need to be removed, signs hidden, even small things such as a light switch being covered. Elaborate films need set extensions, computer generated imagery, blue/green screening and many other tricks which make an FX shot come to life. Layer upon layer give the shot reality, depth and feeling.

Then finally the scene hits a grading suite, a multitude of layered colour changes and tweaks are added changing the whole dynamic of the shot. Hopefully this tiny FX piece will give you a small understanding of what goes into a single effect and what makes a feature film work? Remember there can be hundreds, if not thousands of effects per production.