Canon PowerShot

Digital IXUS is the name in Europe and Southeast Asia for a series of ultra-compact digital cameras by Canon. In the U.S. and Canada, it is called PowerShot Digital ELPH and in Japan, IXY Digital.It is very similar in design to the once very popular Canon IXUS/IXY/ELPH line of Advanced Photo System (APS) film cameras.

Digital IXUS models

The same camera models are released in Europe, the US and Japan under different names. The cameras themselves are identical apart from the front fascia, according to the parts lists. The Canon model number on the bottom is consistent between marketing names.All models use lithium ion batteries of Canon proprietary design, though third-party equivalents are readily available.All models use RGBG Bayer filter (except the original Digital IXUS, which uses a CYGM filter CCD sensors made by Sony. Images are recorded as JPEGs. Raw image files are not accessible.

Digital IXUS: Digital IXUS

PowerShot Digital ELPH: S100

IXY Digital: IXY Digital

Canon model: PC1001

Sensor: 2MP (1600×1200), 1/2.7"

Lens (35mm equiv), zoom, aperture: 35-70 mm (2×)

Card: CF

Battery: NB-1L

Size (mm), weight (inc batt): 87 × 57 × 26.9, 210g

Notes: Only Ixus with a CYGM CCD (all others are RGBG)

Digital IXUS: 65

PowerShot Digital ELPH: SD630
IXY Digital: 80
Canon model: PC1147
Sensor: 6MP

Lens (35mm equiv), zoom, aperture: 35-105 mm (3×)

Card: SD
Battery: NB-4L
Size (mm), weight (inc batt): 90.3 × 56.8 × 20.2, 175g

Notes: IXUS 60 with larger LCD (3 inch) and no viewfinder

Digital single-lens reflex camera

A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that uses an automatic mirror system placed between the lens and the image sensor to direct the image from the lens through the viewfinder where it can be viewed by the photographer. The viewfinder includes a matte focusing screen at its focal plane, to allow accurate focusing and to allow the light into the prism that directs the light through the viewfinder.
The basic operation of a DSLR, having the mirror reflecting the image away from the image sensor except briefly during the exposure, precludes the ability to see the image in the LCD display before the picture is taken, a major difference from the way an ordinary digital camera (digicam) works. Some newer DSLR models feature live preview allowing the image to be seen on the LCD display, although with certain limitations and with the optical viewfinder disabled.
In most other respects a DSLR is similar in principle and operation to a standard digital camera; the image captured by the CCD or CMOS image sensor is processed electronically and stored on a removable memory device. The price range and extra features and options available vary widely from model to model, and newer and better models arrive every year.

DSLR design principles

Cross-section view of SLR system.1 - lens assembly2 - mirror3 - focal-plane shutter4 - sensor5 - matte focusing screen6 - condensing lens7 - pentaprism8 - eyepiece
A camera based on the single-lens reflex (SLR) principle uses a mirror to show the image that will be captured in a viewfinder. The cross-section (side-view) of the optical components of an SLR shows how the light passes through the lens assembly (1), is reflected into the pentaprism by the reflex mirror (which must be at an exact 45 degree angle) (2) and is projected on the matte focusing screen (5). Via a condensing lens (6) and internal reflections in the roof pentaprism (7) the image is projected, either focused or unfocused through the eyepiece (8) to the photographer's eye. Focusing is usually automatic, activated by pressing half-way on the shutter release or a dedicated AF button, as is mainly the case with an autofocusing film SLR; or manual, where the photographer manually focuses the lens by turning a lens ring on the lens barrel. When an image is photographed, the mirror moves upwards in the direction of the arrow, the focal-plane shutter (3) opens, and the image is projected and captured on the sensor (4), after which actions, the shutter closes, the mirror returns to a critical 45 degree angle, and the diaphragm reopens and the built in drive mechanism retensions the shutter for the next exposure.

Fast phase-detection autofocus
The diagram shown here is an over-simplification in that it omits the sensors used to drive the autofocus system.
DSLRs typically use a phase detection autofocus system. This method of focus is very fast, and results in less focus "searching", but requires the insertion of a special sensor into the optical path, so it is usually only used in SLR designs. Digicams that use the main sensor to create a live preview on the LCD or electronic viewfinder need to use the slower contrast method of autofocus.

DSLR optical viewfinder vs. digicam LCD display
Depending on the position of the reflex mirror (down or up), the light from the scene can only reach either the viewfinder or the sensor. Therefore, most DSLRs do not currently provide "live preview" (allowing focusing, framing, and depth-of-field preview using the display), a facility that is always available on digicams.
The advantages of an optical viewfinder are that it alleviates eye-strain sometimes caused by electronic view finders (EVF), and that it constantly shows (except during the split second of time for the sensor to be exposed) the exact image that will be exposed because its light is routed directly from the lens itself. Compared to ordinary digital cameras with their LCD displays and/or electronic viewfinders the advantage is that there is no time lag in the image; it is always correct as it is being "updated" at the speed of light. This is important for action and/or sports photography, or any other situation where the subject or the camera is moving too quickly. Furthermore, the "resolution" of the viewed image is much better than that provided by an LCD display or an electronic viewfinder, which can be important if manual focusing is desired for precise focusing, as would be the case in photomacrography or photomicrography (commonly referred to as "macro-photography" and "micro-photography").
Compared to some low cost cameras that provide an optical viewfinder that uses a small auxiliary lens, the DSLR design has the advantage of being parallax-free; that is, it never provides an off-axis view.
A disadvantage of the DSLR optical viewfinder system is that it prevents the possibility of using the LCD display for viewing and composing the picture before taking it. Some people prefer to compose pictures on the display – for them this has become the natural way to use a camera. LCD displays and electronic viewfinders may also provide a brighter display in low light situations, as the picture can be electronically amplified; conversely, LCD displays can be difficult to see in very bright sunlight.

DSLRs with live preview
A fairly recent development in DSLRs is the emergence of live preview options, which make it possible to use either the optical viewfinder or the LCD display when composing the picture (but not both). This can be an advantage because some people simply prefer to use the display and because in some situations it is not convenient or possible to hold the camera up to your face to look through the viewfinder. Underwater photography, where the camera is enclosed in a plastic waterproof case, is an example of a situation where composing on the display is preferred.
Olympus introduced the first DSLR with live preview, the Olympus E-330, in the spring of 2006. Since then other manufacturers have launched DSLR models with live preview, and the possibility exists that eventually all new DSLRs will have this feature.
As of the summer of 2007, the Canon EOS-1D Mark III, Canon EOS-1Ds Mark III, Canon EOS 40D, Nikon D3, Nikon D300, Olympus E-330, Olympus E-410, Olympus E-510, Panasonic Lumix DMC-L1, Panasonic Lumix DMC-L10 and Leica Digilux 3 all provide continuous live preview as an option. Additionally, the Fujifilm FinePix S5 Pro offers 30 seconds of live preview.

Classification cameras

Classification
Digital cameras can be classified into several categories:

Video cameras
Video cameras are classified as devices whose main purpose is to record moving images.
Professional video cameras such as those used in television and movie production. These typically have multiple image sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
Camcorders used by amateurs. They generally include a microphone to record sound, and feature a small liquid crystal display to watch the video during taping and playback.
Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.
In addition, many Live-Preview Digital cameras have a "movie" mode, in which images are continuously acquired at a frame rate sufficient for video.

Live-preview digital cameras

Canon PowerShot A95 with CompactFlash card loaded
Main article: Live-preview digital camera
The term digital still camera (DSC) most commonly refers to the class of live-preview digital cameras, cameras that use an electronic screen as the principal means of framing and previewing before taking the photograph. All use either a charge-coupled device (CCD) or a CMOS image sensor to sense the light intensities across the focal plane.
Many modern live-preview cameras have a movie mode, and a growing number of camcorders can take still photographs. However, even a low-end live-preview camera can take better still pictures than a mid-range video camera, and mid-range live-preview cameras have much lower video quality than low-end video cameras; that is, products are not generally optimized for both still and video photography, due to their different requirements.
Among live-preview cameras, most have a rear liquid crystal display for both preview and reviewing photographs. Transfers to a computer are commonly carried out using the USB mass storage device class (so that the camera appears as a drive) or using the Picture Transfer Protocol (PTP) and its derivatives; in addition, Firewire is sometimes supported.
The live-preview cameras are typically divided into compact (and subcompact) and bridge cameras.


Compact digital cameras

Also called digicams, this encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They tend to have significantly smaller zooms than bridge and DSLR cameras. They have an extended depth of field. This allows objects at a larger range of depths to be in focus, which accounts for much of their ease of use. They excel in landscape photography and casual use. They typically save pictures in only the JPEG file format. All but the cheapest models have a built-in flash, although its guide number tends to be very low, perhaps just 6 or 8.

Bridge cameras
Main article: Bridge digital camera
Bridge or SLR-like cameras form a general group of higher-end live-preview cameras that physically resemble DSLRs and share with these some advanced features, but share with compacts the live-preview design and small sensor sizes.

Fujifilm FinePix S9000
Bridge cameras tend to have superzoom lenses, which compromises – in varying degrees, depending on the quality of the zoom lens – a "do it all" ability with barrel distortion and pingggcushioning. These cameras are sometimes marketed as and confused with digital SLR cameras since the bodies resemble each other. The distinguishing characteristics are that bridge cameras lack the mirror and reflex system of DSLRs, have so far been always produced with only one single sealed (non-interchangeable) lens (but accessory wide angle or telephoto converters can be attached to the front of the sealed lens), can usually take movies, record audio and the scene composition is done with either the liquid crystal display or the electronic viewfinder (EVF). The overall performance tends to be slower than a true digital SLR, but they are capable of very good image quality while being more compact and lighter than DSLRs. The high-end models of this type have comparable resolutions to low and mid-range DSLRs. Many of the these cameras can save in JPEG or RAW format. The majority have a built-in flash, often a unit which flips up over the lens. The guide number tends to be between 11 and 15.

Ditital camera

A digital camera is an electronic device used to capture and store photographs electronically in a digital format, instead of using photographic film like conventional cameras, or recording images in an analog format to magnetic tape like many video cameras. Modern compact digital cameras are typically multifunctional, with some devices capable of recording sound and/or video as well as photographs. In the Western market, digital still cameras now outsell their 35 mm film counterparts.