Apple Aperture Digital Photography Fundamentals User Manual

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Aperture

Digital Photography Fundamentals

Apple Computer, Inc.

No part of this publication may be reproduced or transmitted for commercial purposes, such as selling copies of this publication or for providing paid for support services. Every effort has been made to ensure that the information in this manual is accurate. Apple is not responsible for printing or clerical errors.

The Apple logo is a trademark of Apple Computer, Inc., registered in the U.S. and other countries. Use of the “keyboard” Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws.

Apple, the Apple logo, Apple Cinema Display and ColorSync are trademarks of Apple Computer, Inc., registered in the U.S. and other countries.

Aperture is a trademark of Apple Computer, Inc.

Preface 5 An Introduction to Digital Photography Fundamentals

Chapter 1 7 How Digital Cameras Capture Images

Types of Digital Cameras

Digital Single-Lens Reflex (DSLR)

Digital Rangefinder

Camera Components and Concepts

12 14 14 15 16 17 17

20 20

21 21 21

22 22 22 22 23 25

Lens Understanding Lens Multiplication with DSLRs Understanding Digital Zoom Aperture Understanding Lens Speed Shutter Using Reciprocity to Compose Your Image Digital Image Sensor Memory Card External Flash

Understanding RAW, JPEG, and TIFF

RAW Why Shoot RAW Files? JPEG TIFF

Shooting Tips

Reducing Camera Shake Minimizing Red-Eye in Your Photos Reducing Digital Noise

Chapter 2 27 How Digital Images Are Displayed

The Human Eye’s Subjective View of Color

Understanding How the Eye Sees Light and Color

Sources of Light

The Color Temperature of Light How White Balance Establishes Color Temperature

32 33 33 34 34 35 35 36 36

Measuring the Intensity of Light Bracketing the Exposure of an Image

Understanding How a Digital Image Is Displayed

Additive vs. Subtractive Color Understanding Color Gamut Displaying Images Onscreen The Importance of Color Calibrating Your Display Apple Cinema Displays Are Proof Perfect Displaying Images in Print Printer Types

Chapter 3 37 Understanding Resolution

Demystifying Resolution

37 38 40

41 41

42 42 42 43 43 44 45

Learning About Pixels

Learning About Bit Depth How Resolution Measurement Changes from Device to Device Mapping Resolution from Camera to Printer

Camera Resolution

Display Resolution

About the Differences Between CRT and Flat-Panel Display Resolutions

Printer Resolution Calculating Color and Understanding Floating Point

Learning About Bit Depth and Quantization

Learning About the Relationship Between Floating Point and Bit Depth

Understanding How Aperture Uses Floating Point

Appendix 47 Credits

Contents

An Introduction to Digital Photography Fundamentals

This document explains digital terminology for the professional photographer who is new to computers and digital photography.

Aperture is a powerful digital photography application designed to help you produce the best images possible. However, many factors outside of Aperture can affect the quality of your images. Being mindful of all these factors can help prevent undesirable results.

The following chapters explain how your camera captures a digital image, how images are displayed onscreen and in print, and how cameras, displays, and printers measure image resolution.

Preface

How Digital Cameras Capture Images

If you’ve previously shot film and are new to digital media, this chapter is for you. Here you’ll find basic information about the types of digital cameras, camera components and concepts, and shooting tips.

People take photographs for many different reasons. Some take pictures for scientific purposes, some shoot to document the world for the media, some make their living shooting products for advertisements, and others shoot for enjoyment or purely artistic purposes. Whatever your reason for picking up a camera and framing an image, an understanding of how cameras work can help you improve the quality of your images.

This chapter covers:

Types of Digital Cameras (p. 7)

Camera Components and Concepts (p. 11)

Understanding RAW, JPEG, and TIFF (p. 21)

Shooting Tips (p. 22)

Types of Digital Cameras

In its most basic form, a digital camera is a photographic device consisting of a lightproof box with a lens at one end, and a digital image sensor at the other in place of the traditional film plane. Advances in digital photography are fast providing a wide spectrum of features and options that can be challenging for the new digital photographer to master.

There are two basic types of digital cameras: digital single-lens reflex (DSLR) and digital rangefinder.

Digital Single-Lens Reflex (DSLR)

This camera is named for the reflexing mirror that allows you to frame the image through the lens prior to capturing the image. As light passes through the DSLR camera’s lens, it falls onto a reflexing mirror and then passes through a prism to the viewfinder. The viewfinder image corresponds to the actual image area. When the picture is taken, the mirror reflexes, or moves up and out of the way, allowing the open shutter to expose the digital image sensor, which captures the image. Most features on a DSLR are adjustable, allowing for greater control over the captured image. Most DSLR cameras also allow the use of interchangeable lenses, meaning you can swap lenses of different focal lengths on the same camera body.

Viewfinder (shows the actual image frame)

Reflexing mirror

(swung open)

Prism

Digital image sensor

Mirror

Lens

Processor

8 Chapter 1

How Digital Cameras Capture Images

Digital Rangefinder

There are two classes of digital rangefinder cameras: coincident rangefinder and point-and-shoot.

Coincident Rangefinder

Unlike DLSR cameras, the coincident rangefinder does not provide the photographer with the ability to view the subject through the lens. Instead, the coincident rangefinder employs a mirror or prism that uses triangulation to unite the images seen through the viewfinder and a secondary window to bring the subject into focus. The photographer sees two images overlaid on top of one another in the viewfinder, and the image is not in focus until there is a single image. As with DSLRs, most features in a coincident rangefinder are adjustable, allowing for maximum control over the captured image. An advantage to using a coincident rangefinder over a DSLR is that the lack of a reflexing mirror significantly reduces camera shake. Camera shake is due to hand movement or the vibration of the reflexing mirror found in a DSLR, and can cause blurring of the image.

Viewfinder

Semitransparent

mirror

Image sensor

Out of focus

(image overlays not aligned)

Beamsplitter semitransparent mirror

Light-gathering window

Reflective

Rotating mirror/prism

Light source

light

In focus

(image overlays aligned)

Chapter 1

How Digital Cameras Capture Images

Digital Point-and-Shoot

This is a lightweight digital camera, aptly named after the two steps required of the photographer to capture an image. Basically, point-and-shoot cameras require pointing the camera and taking the picture without manually adjusting settings such as the aperture, shutter speed, focus, and other settings that professional photographers routinely set on more sophisticated cameras. Of course, some point-and-shoot digital cameras do include adjustable aperture and shutter settings. Point-and-shoot digital cameras are generally light and small, have built-in automatic flash, require no adjusting of focus, and most often include an LCD display that allows you to view the image through the lens in real time via the digital image sensor. Most manufacturers of point-and-shoot cameras separate the viewfinder from the lens assembly to simplify construction and achieve a compact size. The lens, aperture, and shutter are one assembly, irremovable from the camera itself.

LCD display

Viewfinder (shows an approximation of the image frame)

Light source

Reflective

light

LensDigital image sensor

Because rangefinder cameras separate the optical path between the viewfinder and the lens assembly, optical compression and frame indicators (guidelines) are used to approximate the image’s frame. This approximation often causes subtle differences between what the photographer sees in the viewfinder and what is captured in the image. This is especially noticeable when the subject is close to the camera.

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How Digital Cameras Capture Images

Camera Components and Concepts

The basic components of a DSLR are described below. (Most of the components in a rangefinder are also found in a DSLR.)

Lens

Aperture

Shutter

Digital image sensor

Memory card

External flash

Lens

A lens is a series of sophisticated elements, usually glass, constructed to refract and focus the reflective light from a scene at a specific point—the digital image sensor.

LCD display

Viewfinder

Light source

LensDigital image sensor

Reflective

light

Beyond framing an image, the first interaction you have with the reflective light from your subject is through your camera’s lens.

Chapter 1

How Digital Cameras Capture Images

Focal Length

An important attribute of a lens, besides its quality, is its focal length.

Focal length

is technically defined as the distance from the part of the optical path where the light rays converge to the point where the light rays passing through the lens are focused onto the image plane—or the digital image sensor. This distance is usually measured in millimeters. From a practical point of view, focal length can be thought of as the amount of magnification of the lens. The longer the focal length, the more the lens magnifies the scene. In addition to magnification, the focal length determines the perspective and compression of the scene.

Digital image sensor

Focal length Light

Lens

Camera body

(side view)

Understanding Lens Multiplication with DSLRs

Most interchangeable lenses were originally created and rated for the 35 mm film plane of traditional SLRs. If you compare the area of a 35 mm film plane with the area of most digital image sensors’ image planes, you’ll see that the area of most digital image sensors is a bit smaller. The focal length of a lens changes when it is put on a DSLR with a digital image sensor smaller than 35 mm. This smaller image plane effectively increases the focal length of the lens because more of the image circle coming out of the lens is cropped. For example, if you put a 100 mm lens on a DSLR that has a 24 mm digital image sensor, the focal length of the lens is multiplied by a factor of approximately 1.3. A 100 mm lens with a 1.3x multiplication factor effectively becomes a 130 mm lens (100 mm multiplied by 1.3).

Another reason to take lens multiplication into account is that shooting wide-angle images becomes increasingly difficult when using cameras with smaller digital image sensors. For example, if your digital image sensor is 24 mm, you require a lens with a focal length less than 24 mm to achieve a wide-angle view. Check your camera specifications for the size of your digital image sensor.

12 Chapter 1

How Digital Cameras Capture Images

Lens Types

Although there are many varieties of lenses, common lens types include telephoto, wideangle, zoom, and prime. All of these lenses perform the same basic function: they capture the reflective light from the subject and focus it on the image sensor. However, the way they transmit the light differs.

Note:

Although there are several subcategories and hybrids of these lens types, these

are the most basic.

Telephoto

A telephoto lens is a lens with a long focal length that magnifies the subject. Telephoto lenses are typically used by sports and nature photographers who shoot their subjects from great distances. Telephoto lenses are also used by photographers who want greater control over limiting the depth of field (the area of an image in focus). The larger aperture settings, combined with the long focal lengths of telephoto lenses, can limit the depth of field to a small area (either the foreground, middle, or background of the image). Small aperture settings, combined with long focal lengths, make objects in the foreground and background seem closer together.

Wide-Angle

A wide-angle lens is a lens with a short focal length that takes in a wide view. Wideangle lenses are typically used when the subject is in the extreme foreground and the photographer wants the background in focus as well. Traditionally, the focal length of a wide-angle lens is smaller than the image plane. However, in the digital photography age, the sizes of image sensors vary, and the lens multiplication factors of most DSLRs increase the focal length. Check the specifications of your camera to ascertain the size of your digital image sensor. If the size of your digital image sensor is 28 mm, you require a lens with a focal length less than 28 mm to achieve a wide-angle view.

Chapter 1

How Digital Cameras Capture Images

Zoom

A zoom lens, also known as an its focal length. A zoom lens can be extremely convenient, because many zoom lenses can change their focal lengths from wide-angle to standard and from standard to zoom. This eliminates the need to carry and change multiple lenses while shooting a subject or project. However, because of the movement between focal lengths, the f-stops aren’t always entirely accurate. To achieve a greater level of accuracy with apertures, many manufacturers have multiple minimum aperture values as the lens moves from a shorter focal length to a longer one. This makes the lens slower at longer focal lengths. (See “Understanding Lens Speed” on page 15 for an explanation of lens speed.) Plus, a zoom lens requires additional glass elements to correctly focus the light at different focal lengths. It is desirable to have the light pass through the least amount of glass in order to obtain the highest-quality image possible.

optical zoom lens,

has the mechanical capacity to change

Understanding Digital Zoom

The digital zoom feature offered by some camera models does not really zoom in closer to the subject. Digital zoom crops into the center area of the captured frame, effectively enlarging the pixels. This results in a picture with a lower overall image quality. If you don’t have a telephoto or optical zoom lens and you want a close-up, physically move closer to the subject, if you can.

Prime

A prime lens, also known as a Prime lenses often have wider maximum apertures, making them faster. For more information about lens speed, see “Understanding Lens Speed” on page 15. Wider apertures allow for brighter images in low-light situations, as well as greater control over depth of field. Prime lenses are primarily used by portrait photographers. For more information on depth of field, see “Depth of Field” on page 15.

fixed lens,

has a fixed focal length that is not modifiable.

Aperture

The aperture is the opening in the lens (created by an adjustable iris or diaphragm) that allows light to pass through. The exposure of the image is determined by the combination of shutter speed and the opening of the aperture. The larger the aperture, the more light is allowed to pass through the lens. The aperture is measured in f-stops, and each stop represents a factor of two in the amount of light admitted. The aperture setting (f-stop), combined with the focal length of the lens, determines the depth of field of an image. For more information on depth of field, see “Depth of Field” on page 15.

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How Digital Cameras Capture Images

f-stop

The photographer adjusts the opening of the aperture by setting the f-stop. An f-stop is a ratio of the focal length of the lens to the diameter of the opening of the aperture. For example, a 50 mm lens with an aperture opened up to a diameter of 12.5 mm results in an f-stop of f4 (50 ÷ 12.5 = 4). Therefore, the larger the numerical value of the f-stop, the smaller the opening of the aperture. The speed of a lens is determined by its largest f-stop value (smallest number). Thus, the larger the aperture, the faster the lens.

f2 f2.8 f4 f5.6

f8 f11 f16 f22

Understanding Lens Speed

A lens’s speed is determined by the maximum amount of light the lens is capable of transmitting—the largest f-stop value. When a lens is capable of transmitting more light than other lenses of the same focal length, that lens is referred to as allow photographers to shoot at higher shutter speeds in low-light conditions. For example, lenses with maximum f-stop values between 1.0 and 2.8 are considered fast.

Depth of Field

Depth of field is the area of the image that appears in focus from foreground to background and is determined by a combination of the opening of the aperture and the focal length of the lens. A small aperture setting results in greater depth of field. Controlling depth of field is one of the easiest ways for a photographer to compose the image. By limiting the depth of field of an image, the photographer can turn the attention of the viewer on the subject in focus. Often, limiting the depth of field of an image helps eliminate clutter in the background. On the other hand, when shooting a landscape, you want the image to have great depth of field. Limiting the depth of field to the foreground would not make sense.

fast

. Fast lenses

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