A
digital camera or
digicam is a
camera that encodes
digital images and
videos digitally and stores them for later reproduction.
[1] Most cameras sold today are digital,
[2] and digital cameras are incorporated into many devices ranging from
PDAs and
mobile phones (called
camera phones) to vehicles.
Digital and
film cameras share an optical system, typically using a lens with a variable
diaphragm to focus light onto an image pickup device.
[3]
The diaphragm and shutter admit the correct amount of light to the
imager, just as with film but the image pickup device is electronic
rather than chemical. However, unlike film cameras, digital cameras can
display images on a screen immediately after being recorded, and store
and delete images from
memory. Many digital cameras can also record moving videos with
sound. Some digital cameras can
crop and
stitch pictures and perform other elementary
image editing.
History
The history of the digital camera began with
Eugene F. Lally of the
Jet Propulsion Laboratory,
who when he wasn't coming up with ways to create artificial gravity was
thinking about how to use a mosaic photosensor to capture digital
images. His 1961 idea was to take pictures of the planets and stars
while travelling through space to give information about the astronauts'
position. Unfortunately, as with
Texas Instruments employee Willis Adcock's filmless camera (US patent 4,057,830) in 1972, the technology had yet to catch up with the concept.
Steven Sasson as an engineer at
Eastman Kodak invented and built the first electronic camera using a
charge-coupled device image sensor in 1975.
[4] Earlier ones used a
camera tube;
later ones digitized the signal. Early uses were mainly military and
scientific; followed by medical and news applications. In the mid to
late 1990s digital cameras became common among consumers. By the
mid-2000s digital cameras had largely replaced film cameras, and
higher-end cell phones had an integrated digital camera. By the
beginning of the 2010s almost all
smartphones had an integrated digital camera.
Image sensors
The two major types of digital image sensor are
CCD and
CMOS. A CCD sensor has one amplifier for all the pixels, while each pixel in a CMOS
active-pixel sensor has its own amplifier.
[5] Compared to CCDs, CMOS sensors use less power.
[6] Cameras with a small sensor use a
back-side-illuminated
CMOS (BSI-CMOS) sensor. Overall final image quality is more dependent
on the image processing capability of the camera, than on sensor type.
[6][7]
Sensor resolution
Image at left has a higher pixel count than the one to the right, but has lower
spatial resolution.
The
resolution of a digital camera is often limited by the image sensor
[8]
that turns light into discrete signals. The brighter the image at a
given point on the sensor, the larger the value that is read for that
pixel. Depending on the physical structure of the sensor, a
color filter array may be used, which requires
demosaicing to recreate a full-color image. The number of pixels in the sensor determines the camera's "
pixel count".
In a typical sensor, the pixel count is the product of the number of
rows and the number of columns. For example, a 1,000 by 1,000 pixel
sensor would have 1,000,000 pixels, or 1 megapixel.
Methods of image capture
At the heart of a digital camera is a CCD or a
CMOS image sensor.
Digital camera, partly disassembled. The lens assembly (bottom right) is
partially removed, but the sensor (top right) still captures an image,
as seen on the LCD screen (bottom left).
Since the first digital backs were introduced, there have been three
main methods of capturing the image, each based on the hardware
configuration of the sensor and color filters.
Single-shot capture systems use either one sensor chip with a
Bayer filter mosaic, or three separate image sensors (one each for the
primary additive colors red, green, and blue) which are exposed to the same image via a beam splitter (see
Three-CCD camera).
Multi-shot exposes the sensor to the image in a sequence of
three or more openings of the lens aperture. There are several methods
of application of the multi-shot technique. The most common originally
was to use a single image sensor with three filters passed in front of
the sensor in sequence to obtain the additive color information. Another
multiple shot method is called
Microscanning.
This method uses a single sensor chip with a Bayer filter and
physically moved the sensor on the focus plane of the lens to construct a
higher resolution image than the native resolution of the chip. A third
version combined the two methods without a Bayer filter on the chip.
The third method is called
scanning because the sensor moves across the focal plane much like the sensor of an
image scanner. The
linear or
tri-linear
sensors in scanning cameras utilize only a single line of photosensors,
or three lines for the three colors. Scanning may be accomplished by
moving the sensor (for example, when using
color co-site sampling) or by rotating the whole camera. A digital
rotating line camera offers images of very high total resolution.
The choice of method for a given capture is determined largely by the
subject matter. It is usually inappropriate to attempt to capture a
subject that moves with anything but a single-shot system. However, the
higher color fidelity and larger file sizes and resolutions available
with multi-shot and scanning backs make them attractive for commercial
photographers working with stationary subjects and large-format
photographs.
[original research?]
Improvements in single-shot cameras and image file processing at the
beginning of the 21st century made single shot cameras almost completely
dominant, even in high-end commercial photography.
Filter mosaics, interpolation, and aliasing
The Bayer arrangement of color filters on the pixel array of an image sensor.
Most current consumer digital cameras use a
Bayer filter mosaic in combination with an optical
anti-aliasing filter to reduce the aliasing due to the reduced sampling of the different primary-color images. A demosaicing algorithm is used to
interpolate color information to create a full array of RGB image data.
Cameras that use a beam-splitter single-shot
3CCD approach, three-filter multi-shot approach, color co-site sampling or
Foveon X3 sensor do not use anti-aliasing filters, nor demosaicing.
Firmware in the camera, or a software in a raw converter program such as
Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the
RGB color model
requires three intensity values for each pixel: one each for the red,
green, and blue (other color models, when used, also require three or
more values per pixel). A single sensor element cannot simultaneously
record these three intensities, and so a
color filter array (CFA) must be used to selectively filter a particular color for each pixel.
The Bayer filter pattern is a repeating 2x2 mosaic pattern of light
filters, with green ones at opposite corners and red and blue in the
other two positions. The high proportion of green takes advantage of
properties of the human visual system, which determines brightness
mostly from green and is far more sensitive to brightness than to hue or
saturation. Sometimes a 4-color filter pattern is used, often involving
two different hues of green. This provides potentially more accurate
color, but requires a slightly more complicated interpolation process.
The color intensity values not captured for each pixel can be
interpolated from the values of adjacent pixels which represent the color being calculated.
Sensor size and angle of view
Cameras with digital image sensors that are smaller than the typical 35mm film size have a smaller field or
angle of view when used with a lens of the same
focal length. This is because angle of view is a function of both focal length and the sensor or film size used.
The
crop factor is relative to the
35mm film format.
If a smaller sensor is used, as in most digicams, the field of view is
cropped by the sensor to smaller than the 35mm full-frame format's field
of view. This narrowing of the field of view may be described as
crop factor, a factor by which a longer focal length lens would be needed to get the same field of view on a 35mm film camera.
Full-frame digital SLRs utilize a sensor of the same size as a frame of 35mm film.
Common values for field of view crop in DSLRs using
active pixel sensors include 1.3x for some
Canon (APS-H) sensors, 1.5x for
Sony APS-C sensors used by
Nikon,
Pentax and
Konica Minolta and for
Fujifilm sensors, 1.6 (APS-C) for most Canon sensors, ~1.7x for
Sigma's
Foveon sensors and 2x for
Kodak and
Panasonic 4/3-inch sensors currently used by
Olympus and Panasonic. Crop factors for non-SLR consumer compact and
bridge cameras are larger, frequently 4x or more.
Relative sizes of sensors used in most current digital cameras.
| Table of sensor sizes[9] |
| Type |
Width (mm) |
Height (mm) |
Size (mm²) |
| 1/3.6" |
4.00 |
3.00 |
12.0 |
| 1/3.2" |
4.54 |
3.42 |
15.5 |
| 1/3" |
4.80 |
3.60 |
17.3 |
| 1/2.7" |
5.37 |
4.04 |
21.7 |
| 1/2.5" |
5.76 |
4.29 |
24.7 |
| 1/2.3" |
6.16 |
4.62 |
28.5 |
| 1/2" |
6.40 |
4.80 |
30.7 |
| 1/1.8" |
7.18 |
5.32 |
38.2 |
| 1/1.7" |
7.60 |
5.70 |
43.3 |
| 2/3" |
8.80 |
6.60 |
58.1 |
| 1" |
12.8 |
9.6 |
123 |
| 4/3" |
18.0 |
13.5 |
243 |
| APS-C |
25.1 |
16.7 |
419 |
| 35 mm |
36 |
24 |
864 |
| Back |
48 |
36 |
1728 |
The majority of digital cameras are phone cameras.
Types of digital cameras
Digital cameras come in a wide range of sizes, prices and
capabilities. In addition to general purpose digital cameras,
specialized cameras including
multispectral imaging equipment and
astrographs are used for scientific, military, medical and other special purposes.
Compacts
Subcompact with lens assembly retracted
Disassembled compact digital camera
Compact cameras are intended to be portable (pocketable) and are particularly suitable for casual "
snapshots".
Many incorporate a retractable lens assembly that provides optical
zoom. In most models, an auto actuating lens cover protects the lens
from elements. Most ruggedized or
water-resistant models do not retract, and most with (
superzoom) capability do not retract fully.
Compact cameras are usually designed to be
easy to use.
Almost all include an automatic mode, or "auto mode", which
automatically makes all camera settings for the user. Some also have
manual controls. Compact digital cameras typically contain a small
sensor which trades-off picture quality for compactness and simplicity;
images can usually only be stored using
lossy compression (
JPEG). Most have a built-in
flash usually of low power, sufficient for nearby subjects. A few high end compact digital cameras have a
hotshoe for connecting to an external flash.
Live preview
is almost always used to frame the photo on an integrated LCD. In
addition to being able to take still photographs almost all compact
cameras have the ability to record
video.
Compacts often have
macro capability and
zoom lenses, but the zoom range (up to 30x) is generally enough for
candid photography but less than is available on
bridge cameras (more than 60x), or the interchangeable lenses of DSLR cameras available at a much higher cost.
[10] Autofocus
systems in compact digital cameras generally are based on a
contrast-detection methodology using the image data from the live
preview feed of the main imager. Some compact digital cameras use a
hybrid autofocus system similar to what is commonly available on DSLRs.
Some high end travel compact cameras have 30x optical zoom have full
manual control with lens ring, electronic viewfinder, Hybrid Optical
Image Stabilization, built-in flash, Full HD 60p, RAW, burst shooting up
to 10fps, built-in Wi-Fi with NFC and GPS altogether.
[11]
Typically, compact digital cameras incorporate a nearly silent
leaf shutter into the lens but play a simulated camera sound
[12] for
skeuomorphic purposes.
For low cost and small size, these cameras typically use
image sensor formats
with a diagonal between 6 and 11 mm, corresponding to a crop factor
between 7 and 4. This gives them weaker low-light performance, greater
depth of field,
generally closer focusing ability, and smaller components than cameras
using larger sensors. Some cameras use a larger sensor including, at the
high end, a pricey full-frame sensor compact camera, such as
Sony Cyber-shot DSC-RX1, but have capability near that of a DSLR.
A variety of additional features are available depending on the model of the camera. Such features include ones such as
GPS, compass,
barometer and
altimeter for above mean sea level or under(water) mean sea level.
[13] and some are rugged and
waterproof.
Starting in 2011, some compact digital cameras can take 3D still photos. These 3D compact
stereo cameras can capture 3D panoramic photos with dual lens or even single lens for play back on a
3D TV.
In 2013, Sony released two add-on camera models without display, to be used with a smartphone or tablet, controlled by a
mobile application via WiFi.
[14]
Rugged compacts
Rugged compact cameras typically include protection against
submersion, hot and cold conditions, shock and pressure. Terms used to
describe such properties include waterproof, freezeproof, heatproof,
shockproof and crushproof, respectively. Nearly all major camera
manufacturers have at least one product in this category. Some are
waterproof to a considerable depth up to 82 feet (27 m);
[15]
others only 10 feet (3m), but only a few will float. Ruggeds often lack
some of the features of ordinary compact camera, but they have video
capability and the majority can record sound. Most have image
stabilization and built-in flash. Touchscreen LCD and GPS do not work
underwater.
Action cameras
GoPro and other brands offer action cameras which are rugged, small and can be easily attached to
helmet, arm, bicycle, etc. Most have wide angle and fixed focus, and can take motion and still pictures, usually without sound.
Bridge cameras
Main article:
Bridge camera
Bridge cameras physically resemble DSLRs, and are sometimes called
DSLR-shape or DSLR-like. They provide some similar features but, like
compacts, they use a fixed lens and a small sensor. Some compact cameras
have also PSAM mode. Most use
live preview to frame the image. Their usual autofocus is by the same contrast-detect mechanism as compacts, but many bridge cameras have a
manual focus mode and some have a separate focus ring for greater control.
Big physical size and small sensor allow
superzoom and wide
aperture. Bridgcams generally include an
image stabilization system to enable longer handheld exposures, sometimes better than DSLR for low light condition.
As of 2014, bridge cameras come in two principal classes in terms of
sensor size, firstly the more traditional 1/2.3" sensor (as measured by
image sensor format)
which gives more flexibility in lens design and allows for handholdable
zoom from 20 to 24mm (35mm equivalent) wide angle all the way up to
over 1000mm supertele, and secondly a 1" sensor that allows better image
quality particularly in low light (higher ISO) but puts greater
constraints on lens design, resulting in zoom lenses that stop at 200mm
(constant aperture, e.g. Sony RX10) or 400mm (variable aperture, e.g.
Panasonic Lumix FZ1000) equivalent, corresponding to an optical zoom
factor of roughly 10 to 15.
Some bridge cameras have a lens thread to attach accessories such as wide-angle or
telephoto converters as well as filters such as UV or
Circular Polarizing filter and lens hoods. The scene is composed by viewing the display or the
electronic viewfinder (EVF). Most have a slightly longer
shutter lag than a DSLR. Many of these cameras can store images in a raw format in addition to supporting JPEG.
[16] The majority have a built-in flash, but only a few have a
hotshoe.
In bright sun, the quality difference between a good compact camera
and a digital SLR is minimal but bridge cameras are more portable, cost
less and have a greater zoom ability. Thus a bridge camera may better
suit outdoor daytime activities, except when seeking
professional-quality photos.
[17]
Mirrorless interchangeable-lens cameras
In late 2008, a new type of camera emerged called mirrorless
interchangeable-lens camera (MILC), which uses various sensors and
offers lens interchangeability. These are simpler and more compact than
DSLRs due to not having a lens reflex system. MILC camera models are
available with various sensor sizes including: a small 1/2.3 inch
sensor, as is commonly used in
bridge cameras such as the original
Pentax Q (more recent Pentax Q versions have a slightly larger 1/1.7 inch sensor); a 1 inch sensor; a
Micro Four Thirds sensor; an APS-C sensor such as the Sony NEX series,
Fujifilm X series,
Pentax K-01, and
Canon EOS M; and some, such as the
Sony Alpha 7, use a full frame (35 mm) sensor.
Olympus and Panasonic released many Micro Four Thirds cameras with
interchangeable lenses which are fully compatible each other without any
adapter, while the others have proprietary mounts. In 2014, Kodak
released its first Micro Four Third system camera.
[18]
As of March 2014, MILC cameras are available which appeal to both amateurs and professionals.
[19]
Modular cameras
While most digital cameras with interchangeable lenses feature a
lens-mount of some kind, there are also a number of modular cameras,
where the shutter and sensor are incorporated into the lens module.
The first such modular camera was the
Minolta Dimâge V in 1996, followed by the
Minolta Dimâge EX 1500 in 1998 and the
Minolta MetaFlash 3D 1500 in 1999. In 2009, Ricoh released the
Ricoh GXR modular camera.
At CES 2013,
Sakar International announced the
Polaroid iM1836, an 18 MP camera with 1"-sensor with interchangeable sensor-lens. An adapter for
Micro Four Thirds, Nikon and K-mount lenses was planned to ship with the camera.
[20]
There are also a number of add-on camera modules for
smartphones
called lens-style cameras (lens camera). They contain all components of
a digital camera in a module, but lack a viewfinder, display and most
of the controls. Instead they can be mounted to a
smartphone and use its display and controls. Lens-style cameras include:
- Sony SmartShot QX series, announced and released in mid 2013. In
January 2014 announced a firmware update for Cyber-shot SmartShot DSC-QX10 and DSC-QX100.[21] In September 2014, Sony announced the Cyber-shot SmartShot DSC-QX30 as well as the α SmartShot ILCE-QX1,[22][23] the latter with E-mount instead of a built-in lens.
- Kodak PixPro smart lens camera series, announced in 2014.[24]
- Vivicam smart lens camera series from Vivitar/Sakar, announced in 2014.[25]
- Olympus Air lens camera, announced in 2014 and released in 2015, the lens camera is open platform using Android (operating system) and can detach into 2 parts (sensor part and lens part) and all Micro Four Thirds System lenses can be attached to sensor part of the lens camera.[26][27]
Digital single-lens reflex cameras
Digital
single-lens reflex cameras
(DSLR) use a reflex mirror that can reflect the light and also can
swivel from one position to another position and back to initial
position. By default, the reflex mirror is set 45 degree from
horizontal, blocks the light to the sensor and reflects light from the
lens to penta-mirror/prism at the DSLR camera and after some reflections
arrives at the viewfinder. The reflex mirror is pulled out horizontally
below the penta-mirror/prism when shutter release is fully pressed, so
the viewfinder will be dark and the light/image can directly strike the
sensor at the time of exposure (speed setting).
Autofocus is accomplished using sensors in the mirror box. Some DSLRs have a "
live view" mode that allows framing using the screen with image from the sensor.
These cameras have much larger sensors than the other types,
typically 18 mm to 36 mm on the diagonal (crop factor 2, 1.6, or 1). The
larger sensor permits more light to be received by each pixel; this,
combined with the relatively large lenses provides superior low-light
performance. For the same field of view and the same aperture, a larger
sensor gives shallower focus.
They use
interchangeable lenses
for versatility. Usually some lenses are made for digital SLR use only,
but recent trend the lenses can also be used in detachable lens video
camera with or without adapter.
Digital Single Lens Translucent (DSLT) cameras
A DSLT uses a
fixed translucent mirror instead of a
moving
reflex mirror as in DSLR. A translucent mirror or transmissive mirror
or semi-transparent mirror is a mirror which reflects the light to two
things at the same time. It reflects it along the path to a
pentaprism/pentamirror which then goes to an optical view finder (OVF)
as is done with a reflex mirror in DSLR cameras. The translucent mirror
also sends light along a second path to the sensor. The total amount of
light is not changed, just some of the light travels one path and some
of it travels the other. The consequences are that DSLT cameras should
shoot a half stop differently from DSL. One advantage of using a DSLT
camera is the blind moments a DSLR user experiences while the reflecting
mirror is moved to send the light to the sensor instead of the
viewfinder do not exist for DSLT cameras. Because there is no time at
which light is not traveling along both paths, DSLT cameras get the
benefit of continuous auto-focus tracking. This is especially beneficial
for burst mode shooting in low-light conditions and also for tracking
when taking video.
[citation needed]
Until early 2014, only Sony had released DSLT cameras. By March 2014,
Sony had released more DSLTs than DSLRs with a relatively complete
lenses line-up.
[citation needed]
Digital rangefinders
A rangefinder is a device to measure subject distance, with the
intent to adjust the focus of a camera's objective lens accordingly (
open-loop controller).
The rangefinder and lens focusing mechanism may or may not be coupled.
In common parlance, the term "rangefinder camera" is interpreted very
narrowly to denote manual-focus cameras with a visually-read out optical
rangefinder based on
parallax.
Most digital cameras achieve focus through analysis of the image
captured by the objective lens and distance estimation, if it is
provided at all, is only a byproduct of the focusing process (
closed-loop controller).
Line-scan camera systems
A line-scan camera traditionally has a single row of pixel sensors,
instead of a matrix of them. The lines are continuously fed to a
computer that joins them to each other and makes an image. This is most
commonly done by connecting the camera output to a
frame grabber which resides in a
PCI slot
of an industrial computer. The frame grabber acts to buffer the image
and sometimes provide some processing before delivering to the computer
software for processing.
Multiple rows of sensors may be used to make colored images, or to increase sensitivity by TDI (
Time delay and integration).
Many industrial applications require a wide field of view.
Traditionally maintaining consistent light over large 2D areas is quite
difficult. With a line scan camera all that is necessary is to provide
even illumination across the “line” currently being viewed by the
camera. This makes possible sharp pictures of objects that pass the
camera at high speed.
Such cameras are also commonly used to make
photo finishes,
to determine the winner when multiple competitors cross the finishing
line at nearly the same time. They can also be used as industrial
instruments for analyzing fast processes.
Linescan cameras are also extensively used in imaging from satellites (see
push broom scanner). In this case the row of sensors is perpendicular to the direction of satellite motion. Linescan cameras are widely used in
scanners. In this case, the camera moves horizntally.
Stand alone camera
Stand alone cameras can be used as
remote camera.
One kind weighs 2.31 ounces, with a periscope shape, IPx7
water-resistance and dust-resistance rating and can be enhanced to IPx8
by using a cap. They have no viewfinder or LCD. Lens is a 146 degree
wide angle or standard lens, with fixed focus. It can have a microphone
and speaker, And it can take photos and video. As a remote camera, a
phone app using Android or iOS is needed to send live video, change
settings, take photos, or use time lapse.
[28]
Integration into other devices
Many devices have a built-in digital camera. For example, mobile
phones, PDAs and laptop computers. Built-in cameras generally store the
images in the JPEG file format.
Mobile phones incorporating digital cameras were introduced in Japan in 2001 by J-Phone. In 2003
camera phones
outsold stand-alone digital cameras, and in 2006 they outsold film and
digital stand-alone cameras. Five billion camera phones were sold in
five years, and by 2007 more than half of the
installed base of all mobile phones were camera phones. Sales of separate cameras peaked in 2008.
[29]
Market trends
Sale of smartphones compared to digital cameras 2009-2013
Sales of traditional digital cameras have declined due to the increasing use of
smartphones for casual photography, which also enable easier manipulation and sharing of photos through the use of
apps
and web-based services. "Bridge cameras", in contrast, have held their
ground with functionality that most smartphone cameras lack, such as
optical zoom and other advanced features.
[30][31] DSLRs have also lost ground to
Mirrorless interchangeable-lens camera
(MILC)s offering the same sensor size in a smaller camera. A few
expensive ones use a full-frame sensor as DSLR professional cameras.
[32]
In response to the convenience and flexibility of smartphone cameras,
some manufacturers produced "smart" digital cameras that combine
features of traditional cameras with those of a smartphone. In 2012,
Nikon and Samsung released the
Coolpix S800c and
Galaxy Camera, the first two digital cameras to run the
Android operating system. Since this
software platform is used in many smartphones, they can integrate with services (such as
e-mail attachments,
social networks and
photo sharing sites) as smartphones do, and use other Android-compatible software as well.
[30]
In an inversion, some phone makers have introduced smartphones with
cameras designed to resemble traditional digital cameras. Nokia released
the
808 PureView and
Lumia 1020 in 2012 and 2013; the two devices respectively run the
Symbian and
Windows Phone operating systems, and both include a 41-megapixel camera (along with a camera grip attachment for the latter).
[33] Similarly, Samsung introduced the Galaxy S4 Zoom, having a 16-megapixel camera and 10x optical zoom, combining traits from the
Galaxy S4 Mini with the Galaxy Camera.
[34]
Furthermore, Panasonic Lumic DMC-CM1 is an Android KitKat 4.4
smartphone with 20MP, 1" sensor, the largest sensor for a smartphone
ever, with Leica fixed lens equivalent of 28mm at F2.8, can take RAW
image and 4K video, has 21mm thickness.
[35]
Light-field cameras were introduced in 2013 with one consumer product and several professional ones.
After a big dip of sales in 2012, consumer digital camera sales
declined again in 2013 by 36 percent. In 2011, compact digital cameras
sold 10 million per month. In 2013, sales fell to about 4 million per
month. DSLR and MILC sales also declined in 2013 by 10–15% after almost
ten years of double digit growth.
[3
