Preparation and scene set-up – Lighting Workshop 2

Having a plate image, a couple of reference pictures with the grey sphere, chroma sphere and macbeth chart it is important to match the exposure of the reference footage to the plate. Using Nuke, we first find an object which we will be referencing to. In our case it was a wooden box.

As the file is opened up in Nuke, we note down the average value of the colour in the chosen area taken from the plate. Then the exposure is adjusted for other reference plates the following way:

1) Choose area which we used in reference
2) Create Exposure node in node graph
3) Change ‘Adjust in’ to ‘Stops’
4) Having a reference on values for Red, Blue and Green channels from plate increase the numbers
5) Add ‘Multiply (Math)’ node in the node graph
6) For each channel adjust the value accordingly to match to the earlier noted down values.

Once completing the procedure for other reference pictures, we can move onto creating a North, South domes alongside with any extra HDRIs for too bright lights sources (in this case the fluorescent light). First, it’s important to separate the Low and High Pass to see which sources are too bright. That is done by using the ‘Clamp’ node and Merge nodes with correct operation.

Use of clamp node for Low Pass

As the High Pass is created with the separation of overly bright sources (using ‘Merge (minus)’ node with A being the source and B being source with applied clamp), the fluorescent light is separated out with a use of garbage mask, it is then fed back into the Low pass with a use of ‘Merge (plus)’ node. This way (see below), the balanced light sources are included back. That image is then separated into North and South domes.

Addition of higher exposure light areas into the low pass. Can be seen by lowering the aperture.
Node graph for separation into north and south domes.

A similar procedure is done for the fluorescent light. It is also important to make a so-called ‘Sanity Check’ to make sure that none areas were affected or lost. It is done by merging the north, south domes and fluorescent light passes together and subtracting from the adjusted (in exposure) picture. If the result is black at most exposures other than extreme high numbers, then it’s all done and ready for render out to be put into Maya scene.

Sanity check when all is correct. Note the value of exposure.
Sanity check when something went wrong. Note the value of exposure.

As the scene is now set up in Maya, it’s a good procedure to create separate groups for spheres, reference geometry, SkyDomes and Characters. This way we can easily maneuver the scene and hide/unhide the required groups. Firstly we create the sphere and apply correct textures on those. Then the skydomes are created, separate for each written out HDRI. Those are adjusted in orientation to match the reference plate pictures, which are also positioned in the scene so we can see then in render view.

North Dome
South dome
Fluorescent light dome
Render out picture. Comparison of 3D object and the reference photos (at the bottom).
Hiding the spheres, leaving table top and placing the characters in the scene.

The lighting can still be more adjusted, there are some problems such as warmer tones in the shadows, no reflection of characters in the shiny black surface on table, harsh shadows of those on the table, not enough bounce light.

Lighting in movies – week 1

Starting off the course in Katana, we were talked through understanding the lighting in general, the physical properties of it and how it appears to our eyes. A difference between key, fill and rim light was explained and main aspects to successful recreation of the scene lighting were pointed out. As an exercise we had to find 3 shots from various movies and try to assess the position, direction, intensity and properties of the light.

2001: A Space Odyssey

Looking at how the face is lit and the way the shadows are falling, there is a light source directly above the character as well as coming from the background of the blue-ish tone of the screen. The blue tones are reflected from the skin of the chair and in the bottom center of the shot (by his left hand, on the surface). Judging by the back of the head and top of the shoulders, there maybe a fill light placed from behind of the character. As the contrast is low between the key and fill light, we may conclude that it is a low key, soft lighting. The shot seams to be having cool tones, roughly in the range of 4000K.

Alice in the Wonderland

Immediately the light seems to be quite soft and low key. There is a source coming from above of the character as we have shadows underneath her eyes, on the neck and her chin. It feels like there is no fill in light, maybe quite a subtle one. Looking as if it is a cloudy daylight, the temperature of the shot seems to be in the range of 6000K.

Tomb Raider

Shot out in sunlight, this shot has warm undertones. The light is harsh, but appears to be high key as there isn’t as sharp contrast between the highlights and fill in light. As the face is seen fairly good, there is definitely a fill light coming from the front of him, adding warmer tones to his skin (that judgement is made by looking at the fill in highlights on his nose, cheeks, neck all with yellow/orange warmth). The sun seems to be almost directly above him, meaning it was shot at maybe earlier or later than midday.