T436 - Fall 2007 - Week 2

Lenses & Cameras

Readings B Brown Chapters 3 & 4
Next week: 5, 6 and pp 230-240

Reality check:

• Please push for stories this week. (Take some fliers if you can.) If you receive or have any, please place them into a folder called "scripts" in our Oncourse Resources area. I also would like hard copies as well.
• Jib demo this week in lab
• 1st set of cinema reports
• Next week please bring in your grey card and light meter if you have it. We'll be rating cameras.

Need students to run actors call-out. Need to settle on a date. Jim suggests Saturday or Sunday (Sept 22 or 23).

Chapter 2 review of Design Principles from Brown book:

• Unity
• Balance (or unbalance)
• Visual Tension
• Rhythm
• Proportion
• Contrast
• Texture
• Directionality

3-Dimensional Field

• Depth
• Overlap
• Relative Size
• Vertical Location
• Left to Right
• Linear Perspective
• Foreshortening
• Chiaroscuro
• Atmospheric Perspective (creating haze)

Forces of Visual Organization

• The Line
• The Sinuous Line
• Compositional Triangles
• Horizontals, Verticals, and Diagonals
• The Horizon Line & Vanishing Point
• The Power of the Edge of the Frame
• Open and Closed Frame
• Frame within a Frame
• Balanced and Unbalanced Frame
• Positive and Negative Space
• Movement in the Visual Field

Film & Video Composition

• Rule of Thirds
• Headroom
• Noseroom (Lead or Look Room)

Cameras- A few notes on cameras NOT in the readings:

Major parts of video cameras: lens, beam splitter, CCDs/CMOS, & viewfinder
The lens focuses the light onto an imaging or pickup device. In the old days these were tubes, these days CCDs (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) sensors are used.
Most professional video cameras that have CCDs use a beam splitter, which consists of prisms. The incoming light is split into its primary components, Red Green & Blue and recorded onto three separate CCDs. The CCDs are about the size of a postage stamp and convert the light energy into an electric charge. Before CCDs, cameras used tubes. However a growing number are using single CMOS sensors.

While it might be possible to find a camera with 3 CMOS sensors (Sony's DCR-PC1000 for example), most use one. This permits the camera to function without the need for a beam splitter. CMOS sensors use less power than CCDs.

CCD and CMOS sensor sizes

Most sensors are made in different sizes such as 1/4", 1/3", 1/2", and 2/3". Some of the new HD video cameras use larger CMOS sensors that more closely match standard film sizes such as 35mm. This allows DPs to use their existing collection of 35mm lenses and attachments.

Consumer cameras usually have only one pickup device or three very small CCDs. (1/4" for example.) As the price and quality goes up, so does the size of the CCD. Professional studio cameras generally have larger CCDs. (The Canon HLX1 uses 1/3" CCDs while the Grass Valley cameras in Studio 5 use 2/3" CCDs.) Lens mounts are standardized and matched to the corresponding CCD size. (You'd use a 2/3" lens mount with a camera with 2/3" CCDs.) The bigger the lens mount, the bigger the CCD and the more room for more pixels. Generally speaking, bigger is better and the more pixels a CCD or CMOS sensor has on it the higher the resolution or detail that can be delivered by the camera.

Switching gears: video and film

Why does film look like film and video like video?

List some ways to make video look like “film” during the production phase. (not post)

• lighting
• camera movement
• avoiding zooms
• warming or cooling the scene (false white balancing)
• use widescreen
• limit DOF

A great deal of the cinematic look is limiting the depth of field. Video has a smaller target than 35mm or 70mm film cameras. Because of the smaller target the depth of field is far greater. One of the tricks that DPs who work with video know is to shoot with the aperture wide open. They “starve the camera for light” in order to get a limited DOF.

Sometimes, a large DOF is called for. In the book this is called “deep focus.”

f-stops and T stops

Film cameras often use T stops while video cameras usually have f-stops. The marks are called “witness marks.”

f-stops can be derived mathematically by dividing the focal length by the diameter of the lens opening.

But lenses are imperfect and some of the light entering is lost, thus affecting many elements. T-stops represent the actual amount of light passing through the lens.

Back Focus - Never assume that the back focus is set properly. Back focus = flange focal distance.

To set back focus:

• Use Siemans star 8-10 feet away
• Turn peaking on and to the maximum setting
• Open iris all the way (low light)
• Zoom in & focus
• Zoom out & adjust back focus
• Repeat several times until satisfied

If in doubt, it’s better to underexpose than to overexpose

ASA and ISO are similar- but ASA really refers to B & W

A note on shutter speeds

Do not confuse the idea of using a faster shutter with that of changing the frame rate (over-cranking / under-cranking). Higher shutter speeds do NOT change the frame rate. They simply reduce the duration of the light sample.

Lens

Outside of determining lighting and all elements contained within the frame, the director must determine the height of the lens, the angle (tilt), and possibly the cant, as well as movement.

Why do we move the camera?

Dolly, crane and truck shots provide depth. They move the camera into and through the scene.

Foreground, midground, and background layers and elements are essential to creating a sense of depth.

Have you ever been to an amazing mountaintop and taken a picture? Perhaps you got home and looked at it and were less than impressed. Photos often look compressed and perspective is lost.

Filmmakers are constantly struggling to get depth out of a 2 dimensional frame.

This is why they block action along the Z-axis (towards and away from the camera) and move the camera through the scene.

A static lens is a proscenium and will appear 2-dimensional.

Lens Perspective

Wide angle vs Telephoto

Humans can see at most about a 180 degree field of view. As we focus in on objects our field is much narrower- about 40 degrees.

Extreme wide angle lenses create distortion.

Wide angle lenses also provide Deep Focus (everything appears in focus)

Telephoto lenses compress space. They also reduce the DOF (depth of field)

Selective Focus and Rack Focus are common techniques that rely on a limited DOF.

Image Control

• Filters
• Soft Lenses
• Flare/Glare
• Frame Rate
• Slow Speed Blur
• Shutter Angle
• Time Lapse
• Lens Height
• Tilt
• Reveal
• Movement

Basic lens decisions:

Height in relation to subject
Angle (tilt up or tilt down)
Cant (pitch)
Field of view (expressed in angle or lens size)

Movement:

Tracking
Truck
Dolly
Crane
Pan
Tilt

Reveal – When the camera movement shows us something new, relevant to the story.

Telephoto lenses give the illusion of compressing space

Dollies – Chapman and Fischer dollies can only be leased.

Lab this week:

• Design scene for rotation exercise
• Build set
• Carry out jib exercise

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