Supervising a VFX Shoot Pertemuan 04

Matakuliah : UO666 / DKV Visual FX

Tahun : 2009

Bina Nusantara

BE PREPARED

Before you even reach the set, know your shots inside out, including

know which elements you’ll need to shoot and how they’ll be

photographed. You’ll need to have every unit of photography

covered, and depending on the complexity of the shoot, you may

need assistants for each unit. While one is taking notes, another

could be setting up tracking markers, and a third helping queue

camera moves on the motion control rig. Make sure each assistant

has access to all the equipment they’ll need.

Supervising Shoot

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MEASURE EVERYTHING

You can never collect too much data. Not only will you need to know everything about the camera settings, you’ll also need to know the camera’s relationship to the set, positions of the primary lights, the set’s layout and the positions of the actors. Don’t rely on the Camera Assistant for their camera reports. If they miss vital lens information on a take, you’ll be the one struggling in postproduction. Any data you capture will be used in a variety of situations, from reconstructing precise models of the set in 3D, to matching on-set lighting or camera positions, or tracking live-action footage. While tape measures are fi ne for miniature shoots, it’s worth investing in the more expensive laser range-fi nder for live-action shoots. Also carried by the Camera Assistant, these are good for measuring distance up to about 150m, and are accurate to 1cm or less. When you next need to measure the height of a cathedral ceiling with a tape measure, you’ll wonder why you never made the investment earlier. (You can buy laser measuring devices from

www.microglobe.co.uk.

Supervising Shoot

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TAKE REFERENCE PHOTOGRAPHS

Shoot everything you can with a good quality digital stills camera

– something capable of taking shots in excess of 4MP, and that

can shoot in RAW format (we recommend digital SLRs that offer

exposure bracketing and interchangeable lenses). You’ll need

general reference stills showing each lighting and camera set-up,

as well as the layout of the set. If there’s any possibility you’ll need

to reconstruct elements of the set in 3D, shoot as many texture

references as you can. However great the temptation is to fi re

off the camera fl ash in low-light conditions, don’t use one on set

without warning everyone fi rst. And, as obvious as it may sound,

never fi re a fl ash while fi lming! (This has reportedly been done.)

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SHOOT HDR PANORAMAS

High Dynamic Range (HDR) images, created from multiple exposures

of the same shot, provide a means to light a 3D scene to match a

real-world reference (for more details, see the tutorial on page 58).

Set up your digital camera on a panorama head and take a series of

stills by rotating the camera around its optical centre. Bracket each

exposure fi ve to seven times, either manually by incrementally

varying the aperture one stop from the previous image, or by using

your camera’s auto exposure bracketing function. Overlap the sets

of images to create a 360-degree panorama. The rotation between

overlapping tiles will depend on the lens and resolution. When the

bracketed images are combined using a tool such as HDR Shop, the

HDR log image has a greater dynamic range than the individual

exposures, affording more defi nition to rendered highlights.

Supervising Shoot

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MAKE USE OF LIGHT PROBES

Grey, chrome and white lighting reference balls are used to set up

3D global illumination in the VFX studio. They’re mostly used

mounted on sticks to avoid unnecessary issues with fi ngerprints,

and should be photographed for each lighting and camera set-up.

Leave the fi lm camera in its set-up for the shot; have the Camera

Assistant shoot a VFX slate marked up with the shot number, lens

and focal length; place the lighting reference ball where the main

action occurs, then run a few frames of fi lm. If the action moves

across a large area, shoot the reference balls in positions that span

its breadth. If the camera set-up is far from the action, and the

reference balls are small, you can request a 4K version of the scan.

If you’re striving for perfection, take care when using balls that

aren’t optically perfect. Secondary refl ections caused by ripples on

the surface are quite diffi cult to fi x.

Supervising Shoot

Bina Nusantara

MAKE USE OF LIGHT PROBES

Grey, chrome and white lighting reference balls are used to set up

3D global illumination in the VFX studio. They’re mostly used

mounted on sticks to avoid unnecessary issues with fi ngerprints,

and should be photographed for each lighting and camera set-up.

Leave the fi lm camera in its set-up for the shot; have the Camera

Assistant shoot a VFX slate marked up with the shot number, lens

and focal length; place the lighting reference ball where the main

action occurs, then run a few frames of fi lm. If the action moves

across a large area, shoot the reference balls in positions that span

its breadth. If the camera set-up is far from the action, and the

reference balls are small, you can request a 4K version of the scan.

If you’re striving for perfection, take care when using balls that

aren’t optically perfect. Secondary refl ections caused by ripples on

the surface are quite diffi cult to fi x.

Supervising Shoot

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THE GREY BALL

Images of the grey ball are used to fi gure out the direction of the

keylight when setting up a 3D scene for global illumination. The

18 per cent grey tone appears neutral to the human eye, and is

equivalent to the average Caucasian skin tone. There’s no need to

buy a special-purpose visual effects grey ball – any medium-size

spherical, wooden or Styrofoam ball, available from a crafts shop,

will serve the purpose. First, coat the ball with a white base-paint,

then paint with an 18 per cent grey, matching the swatch to a grey

reference card (this can be purchased from www.amazon.com).

Type Of Light Probes

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THE CHROME BALL

As an alternative to shooting a HDR panorama of the set, the

chrome ball (or ‘mirror ball’), provides the necessary data needed

for setting up 3D refl ection environments. To get full, complete

coverage of the set, you’ll need to shoot the ball twice, from

opposite sides, so that each hemisphere is represented. Specialpurpose

chrome balls come in a range of sizes, so choose the sizes

you’ll need according to your camera set-ups and location. If there’s

only time to shoot one angle, photograph it matching the fi lm

camera’s aperture for equal depth of fi eld, and from as far away as

possible with a fairly small ball (6-8cm). Calibrate your chrome ball

for colour by placing a white card visible in both the frame and the

refl ection within the chrome bal

Type Of Light Probes

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THE WHITE BALL

Many VFX supervisors just shoot grey and chrome balls. Shooting a

white lighting reference ball provides additional information about

multicoloured lights.

Type Of Light Probes