My photography

Shutter and Aperture

Controlling Exposure

In order for an image to be captured on film, it must be exposed to light. The camera has two settings that control light, and they work very similar to the human eye.

The Shutter:

The shutter blocks all light from exposing the film UNTIL you press the button. Then it quickly opens and closes, giving the film a brief flash of light.

You can control the length of time the shutter remains open by setting the SHUTTER SPEED.

Longer shutter speeds = more light
shorter shutter speeds = less light

The Aperture:

Before light reaches film, it must pass through an opening called an "Aperture". The aperture is like a pupil. You can control the aperture by setting the "Aperture Opening", also known as an F-Stop.

Smaller F-stops numbers = larger openings
larger openings = more light

brightness is reduced as light passes through an aperture.

Shutter Speed:
Determines HOW LONG the shutter stays open.

The longer exposures ( like 1 second ) give much more light to the film than a 1/1000 of a second exposure. So even though the number may look bigger, don't be deceived!

Examples:
A half second exposure is ONE STOP darker than a one second exposure.
A 1/125 exposure is TWO STOPS brighter than a 1/500 exposure.

A 1/1000 exposure is THREE STOPS darker than a 1/125 exposure.

Aperture Settings (F-Stops):
Like the pupil in a human eye, the aperture on a camera controls light.

It does so by closing up to restrict light, and opening up to let it through.

Examples:
moving from f/16 to f/8 is:
TWO STOPS brighter.
moving from f/5.6 to f/8 is:
ONE STOP darker
moving from f/4 to f/2.8 is:
ONE STOP brighter

Balancing Shutter and Aperture:

Exposure is about different combinations of shutter and f-stop settings. These combinations can drastically affect the finished picture. For example, the following three pictures have been given an equal amount of light, but the f-stop and shutter combinations make each one unique.

Why is the background all blurred in the right picture, and sharpest in the left ? Because if the exposure is made with a wide aperture ( like f2.8 ), then objects farther away from the subject are thrown farther out of focus. This effect is referred to as "depth of field"

So.. if the aperture is small (like f22) then objects in the background (and foreground ) will appear sharper. However, since more light was required to make the exposure on the left ( 1/4 Second ) the subjects became blurred from MOTION. At 1/250th of a second, the shutter is fast enough to freeze motion.

Stops: The Unit of Exposure

A "stop" is a relative measurement of light.

The term "stop" is used in every aspect of photography to represent a relative change in the brightness of light. For example: If you start with a single lightbulb and then add another bulb, the light intensity will increase by one stop. To increase the light by another stop you would need to double the light for a total of 4 bulbs, and so on..



Double the light is one stop brighter (+1 stop), Half the light is one stop darker (-1 stop)

Stops are interchangable
Aperture, shutter, and film settings are all divided up into "stops", even though the numbering systems are different.

The following chart shows common exposure settings. For the sake of example, the default "exposure" is set to 1/125, f8, ISO100. Don't worry about the numbers for now, because one step = one stop, regardless of which setting you move.

For example:

125 f/5.6 ASA100 is as bright as:
250 f/4 ASA100 which is as bright as:
500 f/4 ASA200

Introduction to Exposure

The moment of exposure:
Most of the time, the inside of the camera is totally dark. When a photograph is taken, the camera opens and light from outside floods in through the lens. Light is projected onto film to make the exposure.

Whether you use traditional or digital film, the concepts the same..

Exposure is the measuring and balancing of light

Too much light and the picture will be washed out. Not enough light and the picture will be too dark. A good photograph depends on calculating the exposure settings that will give the film the "right" amount of exposure.

The photographer can control how much natural light reaches film
by adjusting the camera's shutter, aperture, or film speed.

Measuring light (technical exposure)
A good technical exposure will produce a final image that accurately represents the original scene.. Film is light sensitive, and if the exposure is too dark or too bright, the result will not look like "real life".

Beginner's Guide to Photography

Film Speed Rating - ISO / ASA
All film has a speed rating, whether digital or traditional. You may see this number called ASA or ISO (both indicate the film's rated speed). The speed rating describes how quickly the film reacts to light.



Film speed uses stops, just like shutter and aperture
For example, going from ISO 50 to ISO 200 buys you 2 stops more light. Slower films are less sensitive and generally require longer exposures / more light. Faster films react rapidly, and can be used in low light situations.



lower numbers = slower films = need more light = longer exposures
higher numbers = faster films = need less light = shorter exposures

Film Speed vs. Contrast and Grain
The trade-off between slow and fast films is quality. Slow films generally produce sharper, more detailed images, while faster films often have higher contrast and grain.