Photography The Basics Week 4 Exposure Shutter & Aperture ... Aperture Stops We've already discussed

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  • PHOTOGRAPHY CLASSES

    387 TORRINGTON ROAD·LITCHFIELD·CT·06759 WWW.LITCHFIELDHILLSPHOTOGRAPHY.COM

    Photography

    The Basics

    Week 4

    Exposure

    Shutter & Aperture Together – It’s a “give and take”……

    Aperture Size x Shutter Speed = Amount of Light (exposure)

    Both shutter speed and aperture affect the amount of light entering the camera. Once you

    know any single combination of shutter speed and aperture that will let in the right amount of

    light, you can change one setting as long as you change the other in the OPPOSITE way.

    For example if you choose to use a faster shutter speed to freeze motion, you'll need to use a

    wider aperture to compensate for the light lost due to the higher shutter speed.

    Or if you use a smaller aperture to increase the depth of field, you'll need to use a slower shutter

    speed to compensate for the light lost due to the smaller lens opening.

    Shutter speed and aperture also affect sharpness. Facts you already know:

    Shutter speed affects the blurriness of moving objects.

    Aperture affects the depth of field – sharpness from near to far.

    This series of images show the give-and-take relationship

    of the shutter speed and aperture. Even though the ex-

    posure is the same for all three images, the results are

    quite different. Image 1 shows how the shutter speed has

    frozen the motion, but the background is out of focus.

    Image 2 shows the background is sharper, but the sub-

    ject is slightly blurred with a slower shutter speed. Image 3

    shows that the subject is now very blurry because of the

    shutter speed, but now the background is very much in

    focus.

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    Exposure Basics

    Exposing properly, letting the right amount of light into the camera, involves understanding just

    three things:

    1. How the shutter speed and the size of the lens opening work together to control the

    amount of light that reaches the media;

    2. The sensitivity of the media to light – the media’s ISO speed;

    3. How to meter the amount of light and then set the camera’s controls, either automatically

    or manually.

    STOP(s)!!!!!!!

    A "stop" is a relative measurement of light.

    The term "stop" comes from the early history of photography. Instead of a modern adjustable aperture, early cameras used a set of drilled wooden panels to control exposure. Each panel had a different size hole cut into the middle, and was used to literally stop light from entering the camera. Photographers would then control exposure by inserting or removing these light-stopping panels. 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 candle and then add another candle, the light intensity will increase by one stop (double the amount of light). To increase the light by another stop you would need to double the light for a total of 4 can- dles, and so on. As you can see, stops become exponential. An increase of 3 stops = 8X the amount of light. (1 candle doubled is 2 - one stop. 2 candles doubled is 4 - one stop. 4 can- dles doubled is 8 - one stop. Total - 3 stops, 8 times the amount of light.) A stop is a stop is a stop. Stops are interchangeable. Aperture, shutter, and media settings are all divided up into "stops", even though the numbering systems are different. ISO Stops

    Your media's sensitivity to light is measured as an ISO (International Standards for Organiza-

    tion) number. The higher the number, the more sensitive the media is to light and therefore

    needs less light for a proper exposure. Higher ISO's (800+) can produce grain (on film) and

    digital noise (on chips) which may be objectionable depending on the image.

    Full ISO stops - 100, 200, 400, 800, 1600, 3200, 6400

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    Shutter Stops

    We've already discussed how the shutter controls the amount of light entering the camera by

    how long it is open (time). Increasing the shutter speed decreases the amount of light. You'll

    notice a "rounding" adjustment between 1/8 and 1/15, and 1/60 and 1/125. Remember,

    we're photographers, NOT mathematicians, and this rounding makes things easy in the long

    run

    Full Shutter stops - 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000

    Aperture Stops

    We've already discussed how the aperture controls the amount of light entering the camera

    by how big or small the lens opening is.

    Full Aperture stops - f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64

    One stop = one stop, regardless of which setting you move.

    For example:

    125 f/5.6 ISO100 is as bright as: 250 f/4 ISO100 which is as bright as: 500 f/4 ISO200

    How Exposure Meters Work

    Exposure = Intensity x Time.

    Exposure meters are designed to measure middle gray.

    Meter Demonstration

    Light Meters

    Reflected-light meters measure the light reflected from a subject. They measure luminance.

    A spot meter reads reflected light from only a very small angle.

    Incident-light meters measure the light falling on a subject. They measure illuminance.

    Some meters can make either reflected or incident readings.

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    Built-in Meters

    Meters built into cameras measure the light reflected or produced by objects in their view

    (reflected-light meters) and then calculate an exposure setting.

    Types of Built In Meters

    Averaging Meter -

    Reads most of the image area and

    calculates an exposure that is the "average"

    of all the tones in the scene.

    Center-Weighted Meter -

    Bases its reading on the light more

    toward the center of the image

    (where most amateurs place their

    subject).

    Spot Meter -

    Calculates its exposure on only a

    small part of the image. You would use this

    when it's important to correctly expose for

    only a small part of the image area.

    Multi-segment Meter -

    This divides the image into areas that are me-

    tered individually and then compared to a se-

    ries of patterns stored in the camera's memory.

    The final exposure has a better chance of

    avoiding problems such as overexposing a

    subject that has a lot of darks in the image.

    A camera may offer several different metering

    modes. SEE YOUR MANUAL

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    Scenes That "Fool" Your Meter

    Certain scenes can cause a meter to produce the wrong exposure.

    The most common situation in which overall metering does not work is one with a subject against a

    much lighter background (or, less common, a subject against a much darker background).

    Light Background Dark Background

    For either situation – get close to the subject – take the reading and then adjust your meter.

    If you are in manual mode - simply get close, meter the subject, then set the shutter and aperture,

    back up and take the photograph.

    If you are on any of the automatic modes, this method of getting closer, getting a reading and

    backing up, won't work because the camera will automatically recalculate the exposure from far-

    ther away. You'll need to learn to override your automatic settings.

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    Overriding Automatic Exposures -

    (Check your manual to determine how these work on YOUR camera.)

    Exposure compensation -Moving the setting to +1 or +2 increases the exposure by one or

    two stops and lightens the image. Moving the setting to -1 or -2 decreases the exposure

    by one or two stops and darkens the image.

    Exposure lock -This override locks in a shutter speed and aperture setting temporarily.

    Move in close to meter the most important part(s) of the image, then lock in your settings,

    then recompose the image and photograph the entire scene at that exposure.

    Backlight button - This override works (as the name suggests) when the background is

    much lighter than the main subject. Depressing the button adds a certain amount of

    exposure (1-1 1/2 stops) to lighten an image. It cannot be used to decrease exposure.

    Substitution Readings

    What do you do if you can’t get close enough to the subject to make a reading, and you don’t

    have a spot meter that can make a reading at a distance?

    Palm reading! Light-toned skin is about one stop lighter than the middle-gray tone for which me-

    ters calibrate an exposure, so if your skin tone is light, give one stop more exposure than the me-

    ter indicates. For dark-toned skin, use the meters settings. Better yet, for more precise exposur