[ [ [ VFX : visual effects, compositing, green-screen and image restoration - Yannis Lehuédé

Artistic visual effects only have the limits of imagination, but also those of technical constraints. It is essential to prepare it before the shooting. Without that, most of it will be much more complicated and longer to achieve... and the creative margin could be reduced ! Thus, if you’re thinking about adding some, I strongly recommend that we work together as soon as possible. To get a clearer idea, here is a series of works that I regularly do in digital VFX


Deleting and replacing elements within the image

A microphone, a boom at the edge of the image can be erased. So can marks on objects, license plates, faces be anonymized, the reflection of film crews in certain mirrors, unwanted people in the camera field, etc. I can also reduce or erase the shadow of a drone. To hide the actors’ safety suspension and cables, the elements that juxtapose the actors, it is often necessary to plan and prepare the elements to be erased on the shoot.
In this collection of shots from the film El pomo Azul (directed by Raquel Troyano and Montse Bodas), there is a sky replacement, the addition and deletion of elements, even with a moving camera. Sometimes these elements have been prepared on set with a chroma-key mask.


Computer screens, smartphones incrustation

It’s often simpler and more flexible to add computer, tablet, and smartphone screens in post production. You will be able to decide later what will be displayed on it and recreate future interactions if they are not yet decided. Thus, when shooting, two options are available : leave a green image on the locked device, or turn it off which allows to keep real reflections. It is essential to leave elements as markers on the device (which will be erased later) to allow repositioning the screen image with precision. It will follow the movements of the device. I also can re-integrate elements that pass in front of the screen (fingers, hair, etc) on top of it.

Motion design pour écrans d’ordinateurs et smartphones

En recréant les interactions sur l’écran d’un plan filmé, on dispose d’une grande liberté créative. Sur la vidéo ci-dessus, j’ai aussi animé toutes les interfaces "interactives", HUD, visibles sur les écrans. Vous pouvez consulter quelques éléments de motion graphics que j’ai réalisés pour des projets similaires.



Adding complex elements in compositing

Inserting filmed elements on green/blue screen into other backgrounds

Today, it seems simple to shoot characters on a plain blue or green background and integrate them into a different setting. However, for a good integration, it is a delicate operation. There are many parameters to take into account during the shooting to replace the background in a convincing way that I shall recommend or supervise during the shooting of the schene. Then the video editor will be able to replace the background in post-production, at least temporarily if it remains delicate.
It is often necessary to collect other elements for a good post-production integration. With a tripod camera, it is important to make sure that the background is properly lit, to avoid shadow casting on the background (unless it should to be used for the final effect). In many cases, I combine several techniques to convincingly erase the background (especially for hair and highlights) and blend the lighting of the two images well.
It is possible to use a moving camera. To do this, visual cues to memorise your movements is necessary.
I can then recreated virtual camera with identical movements (and other parameters that help the visual realism). Here is an example of the breakdown of the steps involved in embedding a character in a virtual scene. The idea of using a 2.5D or full 3D set allows to generate the same matching light-set, introduce reflections of shot elements in the set and various interactions, mixed together.


On set supervision

Most of these visual effects require special arrangements during shooting (and sometimes also during pre-production). Depending on the needs, different tasks will be carried out at this stage. It is important to supervise the VFX and allow communication with the camera and lighting teams.
When using blue/green backgrounds, as the VFX supervisor I will make sure that the background is well lit (it saves time, money and creative latitude for the future). If, in addition, the camera is moving, it will be necessary to place markers on the background (here is a marker file to print).
And if, in addition to the camera movements, it is necessary to insert 3D elements into the shot afterwards, it will be useful to shoot a test pattern with the camera and lens used (here is a warp grid file to print and stick on a thick board).

As the VFX supervisor, I will also take photographs of the set and 360° environment to allow proper integration of certain effects into the shot. I have the equipment needed to do this.

Finally, all these additions and modifications to the images will be integrated with the characteristics of the original images : same light dynamics and colour space, same colour depth. They will be color-corrected with the other shots of the film in the same way. Precision is important because it is not always standard with the widespread consumer software


Below is also a group of operations that I regularly achieve after shooting, without any preparation, as it is more likely shot saving.


Film restoration

Let’s go through the elements that couldn’t be anticipated. During filming, various problems may appear that were not seen until afterwards, on shots that cannot be reshot, putting the whole film at risk. Many of these problems can be solved in post-production, and the cost can be covered by the film’s insurance.
These are some of the problems that can be solved.

Noise removal and image stabilisation

A lot of video-editing software now allows you to do this, as much as you can, but sometimes poorly or inadequately, introducing distortions. Some more advanced or more artisanal tools are at my disposal to perform this task. Here is an example of a comparison of several techniques on a delicate plane to stabilise.

Note : When there are sharp jumps or too much motion blur, the quality of the result may be reduced !

Opposite : an image extracted from a denoised video. In cases where the intensity of the noise is very high (dark image with a low-sensitivity camera), it is possible to lose details or sharpness in the operation.

However, grain can be re-introduced afterwards to give a more natural look. This aspect moves to the colour grading and finishing processes, where the effect can also be further refined in an artistic sense : by adding slight chromatic aberrations, dust, scratches and other treatments that reflects the charm of film (and certain lenses).


Lens distortion correction

Some lenses, the very wide-angles, used when shooting in cramped locations, often have image distortions. I regularily straighten these images (with a slight loss at the edges) to correct the perspective. The methods I use adapt or simulate each lens, to find the closest distortion and compensation (this is why we ask to keep the mention of the model of the lens used, its focal length, etc. in each shot of the film).
In this scene from the film El Pomo Azul, a small camera was placed in the refrigerator. This distortion of the image has been corrected (illustration on the right).

Déformations d’objectif corrigées
(à gauche : avant redressement des perspectives / à droite : après)


Clean-plate : Dust and light halo removal

Sometimes, the camera will print parasite elements on the image, such as reflections, light halos, dust in the camera, on the lens...

If this happens on a key element or during an important scene, you might consider wanting to erase or reduce it in post-production. The time taken to produce this "clean-plate" is variable (much more so than cleaning up the material !). In the mountain example displayed, I reduced the blue halos in motion with a simple colour correction and an animated mask (with color-correction tools). Only some discrete and natural halos remain. In other cases, as above, it is necessary to combine several techniques and/or to paint frame by frame on the video.
The main thing is that these corrections remain perfectly invisible to the viewers.


You may have a look at some work samples up to 2012.

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