Concept Artist
Concept artists create artwork in order to visualize the look of a scene, character or asset and to guide other artists on their roles. This happens during the pre production of the video and its goal is to set the visual tone that the video will take. Their work is based on illustrating ideas based on creative briefs given by the director of the production, and it plays an essential role required to maintain the same visual identity throughout the whole movie.
To work as a concept artist you have to be creative and to know how to interpret ideas and translate it to artwork. The art can come to life through digital or traditional drawing and is mostly 2D still images. Being an illustrator is different from being a concept artist: as the former you’ll draw things based on your emotions, while as the latter, you’ll draw an idea that someone proposed in a way that is not necessarily technically perfect, but that expresses the idea creatively.
The work can be done in any software that has a painting setting, but it’s mostly done in Photoshop. No matter the tool, it is important to know how to reproduce good lightning and how to choose the right combination of colours.
Here’s a video posted by ArtStation showing how is to work as a concept artist at ILM.
Matte Painter
Matte painters are the creative artists behind breathtaking environments pictured in films like Avatar, Mulan and The Martian. They create realistic backgrounds to composite scenes that for some reason couldn’t have been shot, either because it’s a place impossible to be found or really hard to be filmed in. The backgrounds can vary from imagined places, such as a galaxy far far away, a place impossible to be filmed in, such as the Moon, or a place too expensive to be used, like Oxford Street.
Historically the environments were hand painted and filmed as a background behind the actors. Nowadays they are generally digital and can be created in 2D or 3D. Matte painting can consist in working with CGI elements that will be implemented on the backgrounds, or live-action footage that will be composited with the background. The software varies depending on the technique being applied, and it’s up to the artist to choose in which way he would like to work, as long as the end result looks photorealistic. Maya is a good software when there’s the need to model 3D assets, along with ZBrush, commonly used for modelling organic environments. Nuke is the software used for compositing the final piece, although it can also be used for creating an entire environment by using static images to form the 3D aspects of the ambience.
The thing I personally most love about matte painting, is that it can make you travel to places you have never imagined before. Here’s an example of a demo reel of a matte painter artist.
Prep Artist
Prep Artist is an entry level position in the VFX industry whose job is to clean the plate’s background so the compositor can later work on the footage. They remove any unwanted object placed in the shot, such as cars and buildings. They can even remove people when needed! During duty hours, prep artists work closely with compositors, since the former will provide the shot that is going to be composited. They can also work with a roto artist but, depending on the job, they’ll also have to rotoscope the plate.
In order to succeed as a prep artist, the professional needs to be a perfectionist, since they need to recognise where the shot needs to be cleaned even in the minutest detail, and the work can take hours to be done in order to look natural. In terms of software, prep artists usually work with Nuke and are expected to have an understanding in using UV projections.
Here’s an example of a reel of a prep artist.
Compositor
Compositing artists play an essential role in the VFX industry, where they are responsible for the final step of the VFX pipeline. The work consists of layering different elements, such as CGI elements, live-action plates and still images, making them look like they belong to the same place, lightning and position. While prep artists clean the plate, compositors add layers to the plate, being the ones responsible for adding explosions, magic portals and light sabers.
Lightning is the key to good compositing: everything in the scene needs to have the same lightning and colour in order to look cohesive and natural. Sometimes there’s the need to relight a layer to get a better result, and getting that right can be tricky. It’s important to have a good eye in art and design to get the colour and perspective right. Having a good notion of camerawork can be handy too. The way the camera is set when the footage is shot will determine aspects of the film such as the depth of field, angles and distortion, and knowing how to manage that in post production is essential.
Many softwares can be used in compositing, however the most commonly used are Nuke and Houdini.
Here’s an interview with a compositor that works for ILM.