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Exposure.pdf

Exposure

FTV 122E: Digital Cinematography Professor Sélène

Exposure

What factors determine Exposure?

Exposure

Factors that determine Exposure

⚫ ISO

⚫ Aperture (Iris) – F-stop

⚫ Shutter Speed (shutter angle)

⚫ Frame Rate

⚫ Light Intensity – the amount of light falling on the scene

The Exposure Triangle

Exposure is controlled through the intersection of

these three elements:

⚫ ISO – the measure of a digital camera sensor’s sensitivity to light

⚫ Shutter Speed / Shutter Angle – the amount of time that the shutter is open

⚫ Aperture – the size of the opening in the lens when a picture is taken * affects Depth of Field

Each of the three aspects of the triangle relate to

light and how it enters and interacts with the

camera.

ISO

ISO or ASA (sensitivity)

⚫ ISO - 100, 200, 400, 800, 1600, 3200, 6400

⚫ Film speed or Digital sensor’s sensitivity to light

⚫ Digital cameras have a “native” ISO – the ISO the manufacturers claim is most optimal for image quality.

⚫ Still, DPs have done tests and sometimes choose to shoot at different ISOs depending on the circumstances

⚫ Higher ISO results in more image noise

High ISO and Digital Noise

High ISO and Digital Noise

Shutter Speed

⚫ What is Shutter Speed?

⚫ Shutter Angle?

⚫ What does shutter speed determine?

Shutter Speed / Shutter Angle

⚫ Shutter speed refers to the amount of time the shutter remains open to capture the image

⚫ Shutter angle is what the the physical rotating shutter in a film camera is set to

⚫ 180-degree shutter represents “normal” blur of motion

Shutter Angle

Shutter Speed / Shutter Angle

Shutter and Motion Blur

Shutter and Motion Blur

Shutter Speed / Shutter Angle

Fast Shutter Speed

⚫ Saving Private Ryan

⚫ Gladiator

⚫ Black Hawk Down

⚫ 28 Days Later

Slow Shutter Speed

⚫ Chungking Express

⚫ Step printing

⚫ Frame Rate

Aperture

Aperture – a light valve that lets in more or less light

Aperture

Aperture

F-stop

F-stops

⚫ f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45,f/64, f/90, f/128

⚫ Thinking in “stops”

⚫ Stops is the language DPs and Gaffers speak

⚫ How much “over” or “under” exposed

Double Half Principle

The Exposure Triangle

Exposure is controlled through the intersection of

these three elements:

⚫ ISO – the measure of a digital camera sensor’s sensitivity to light

⚫ Shutter Speed – the amount of time that the shutter is open

⚫ Aperture – the size of the opening in the lens when a picture is taken * affects Depth of Field

Each of the three aspects of the triangle relate to

light and how it enters and interacts with the

camera.

Light Intensity ⚫ Light intensity and fall off

⚫ Inverse Square Law

Inverse Square Law of Illumination

Inverse Square Law of Illumination ⚫ If you double the distance between subject and light source, it illuminates a

surface area four times greater than the one before.

⚫ In general, we therefore multiply the distance with itself in order to calculate the enlargement of that surface area.

⚫ However, a larger surface area leads to a light intensity that is inversely proportional to the square of the distance, since the same amount of light has to be distributed onto a larger surface area respectively.

⚫ Therefore, we see light fall-off, meaning a decrease of light intensity. ⚫ In technical terms the inverse-square law reads as follows: The energy (in our

case: light intensity) at location A (subject area) decreases inversely proportional to the square of A’s distance to the energy source (for example, our flash head).

Inverse Square Law of Illumination

Metering

Light Meter

⚫ How to use a Digital

light meter

⚫ What information is

your light meter giving

you?

Depends on whether it’s

Incident vs. Reflectance

(spot) meter

The Zone System

The Zone System

The Zone System