what is exposure?

Answer 1

In photography, exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance.

The "correct" exposure for a photograph is determined by the sensitivity of the medium used. For photographic film, sensitivity is referred to as film speed and is measured on a scale published by the International Organization for Standardization (ISO). Faster film requires less exposure and has a higher ISO rating. Exposure is a combination of the length of time and the level of illumination received by the photosensitive material. Exposure time is controlled in a camera by shutter speed and the illumination level by the lens aperture. Slower shutter speeds (exposing the medium for a longer period of time) and greater lens apertures (admitting more light) produce greater exposures.

An approximately correct exposure will be obtained on a sunny day using ISO 100 film, an aperture of f/16 and a shutter speed of 1/100th of a second. This is called the sunny 16 rule: at an aperture of f/16 on a sunny day, a suitable shutter speed will be one over the film speed (or closest equivalent).

Ultimately there is no such thing as "correct exposure", as a scene can be exposed in many ways, depending on the desired effect a photographer wishes to convey.

Answer 2

Think of "exposure" as what happens when you go in the light. The brighter the light the more exposure, the longer you are in it the more exposure and the more sensitive you are to light effects exposure. Now when you convert this to photography there are the same things playing in effect:
1. The brightness of the light.
2. Sensitivity of the film or sensor (ISO)
3. Exposure time (shutter speed)
4. Lens opening ('f' stop)

All effect exposure and must be kept in balance to produce a well exposed image.

Answer 3

There are 2 kinds of exposure:

decent exposure: a so-so picture or a snapshot, post them here and ask people what they think, then get upset when they tell you the truth

indecent exposure: a misdemeaner usually involving showing parts of your body which ought to be kept to yourself or other consenting adult.

FYI: if you take a decent exposure of an indecent exposure, develop those at home, because the clerks at Walmart's Photo labs have no sense of humor!

Answer 4

Exposure is a product of the interaction of light, aperture, shutter speed and ISO. All 4 of these variables must be in balance to produce a correct exposure.

Light is either natural (sunlight) or artificial (electric light, campfires) or a combination.

The aperture controls the amount of light admitted. At f2 it admits all the light there is; at f16 it admits a tiny amount of light.

f2.8 admits 1/2 as much light as f2
f4 admits 1/2 as much light as f2.8
f5.6 admits 1/2 as much light as f4
f8 admits 1/2 as much light as f5.6
f11 admits 1/2 as much light as f8
f16 admits 1/2 as much light as f11

Suppose we assigned a value of 10,000 to the available light. Our example would look like this:

f2 = 10,000
f2.8 = 5,000
f4 = 2,500
f5.6 = 1,250
f8 = 625
f11 = 312.5
f8 = 156.25

The shutter determines how long the light is allowed to expose our light sensitive surface, whether film or digital sensor. The more light admitted by the lens the faster the shutter speed since with more light less exposure time is needed. Use the following as an example only:

f2 @ 1/2000 sec
f2.8 @ 1/1000 sec
f4 @ 1/500 sec
f5.6 @ 1/250 sec
f8 @ 1/125 sec
f11 @ 1/60 sec
f16 @ 1/30 sec

As less and less light is admitted the shutter stays open longer and longer to correctly expose our light sensitive surface. All 7 exposures in the example would be identical.

ISO is a measurement of the sensitivity to light of a light sensitive surface. ISO 25 would be extremely slow - a lot of light or a very long shutter speed would be required. An ISO this low is "tripod needed" territory - or a really powerful flash. ISO 3200 is extremely high and would be used in very low-light situations where a flash would ruin the mood - or alert your subjects that you were photographing them. The most commonly used ISO's are 100, 200 and 400.

EDIT: I am amused that 3 moronic people gave my answer a Thumbs Down. Oh well. At least I know what I'm talking about and its very doubtful they know anything about anything.

Answer 5

Exposure is the length of time your camera's lens aperture (opening/window) stays open to allow light in to capture your image. Usually expressed in /seconds....the longer the exposure time, the brighter the image will get. Exposure length is determined by what your subject is, and what type of lighting conditions it is under.

Answer 6

al comes down to

shutter speed
aperture
and iso

perhaps get the book
'understanding exposure'

Answer 7

I can't help myself.

Following Lucien's great analogy, over exposure is painful.

Ouch! I didn't do that did I?

Vance

Answer 8

walking around with no clothes on