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.
The first method is often called single-shot, in reference to the number of times the camera's sensor is exposed to the light passing through the camera lens. Single-shot capture systems use either one CCD 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.
The second method is referred to as multi-shot because the sensor is exposed 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 (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information. Another multiple shot method utilized a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to "stitch" together a higher resolution image than the CCD would allow otherwise. 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 a desktop scanner. Their linear or tri-linear sensors utilize only a single line of photosensors, or three lines for the three colors. In some cases, scanning is accomplished 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.
Dramatic improvements in single-shot cameras and RAW image file processing at the beginning of the 21st century made single shot, CCD-based cameras almost completely dominant, even in high-end commercial photography. CMOS-based single shot cameras remained somewhat common.
It is a ordinary that humans are famous from other creatures
by a scientific ability, and man has often been described as a tool-using
animal. The difference is not entirely valid. Some animals do use tools.
Chimpanzees are the most often quoted example, stripping a branch to push it
into an anthill and then eating the tasty termites which cling to the end of
it.
A more modern example of tool-using is that of crows living in a walnut avenue
in the Japanese town of Sendai.
The walnuts are too hard to crack. So the crows have taken to dropping them on
a pedestrian crossing where they are compressed by the passing traffic. When it
is the pedestrians' turn, the crows fly in to bear off the fragments.
But there is a difference between using a tool which
comes to hand, however implausibly, and fashioning one for a purpose. Shaping a
tool for cutting or scraping is a difficult job Such a tool must be made of a
hard material, and the hardest material easily available on the surface of the earth
is stone. But how does one shape a stone without tools?
The history of human technology begins with the finding of how to give stone a
cutting edge. The type of stone found most suitable for the purpose is flint.
As part of NASA's celebration of the 10th anniversary of the
International Space Station, the agency is offering a special 2009
calendar to teachers, as well as the general public.
The
calendar contains photographs taken from the space station and
highlights historic NASA milestones and fun facts about the
international construction project of unprecedented complexity that
began in 1998.
One-Loft Racing is the process of training birds bred by many different
breeders in the same loft, under the same trainer and in the same
conditions (as opposed to trainer against trainer in their own lofts
and usually with their own birds). It is thought to be the fairest
method of proving which bloodline or breeder is best and usually provides the highest amount of prize money.
Pigeons are recorded by electronic timing systems scanning the birds as
they enter the home loft with winners decided by as little as 100th of
a second. The birds are all taken to the same release point and they
return to the same home loft, so therefore it is the fastest bird to
complete the journey from A to B. One loft racing is now becoming very
popular all around the world with fanciers able to compare their
bloodlines on an equal basis against the many other pigeons.
Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.
Orogenic uplift is the result of tectonic plate collisions and results in mountain ranges or a more modest uplift over a large region. The Himalaya were (and are still being) formed by the collision of two continental plates, the Indian and Eurasian Plates. This ongoing collision produced the Tibetan Plateau as well as the Himalaya and associated ranges. The Ozark Plateau is a broad uplifted area which resulted from the Ouachita Orogeny to the south during the Permian Period. Another related uplift is the Llano Uplift in Texas, a geographical location named after its uplift features. The Colorado Plateau with its spectacular scenic canyons, the Grand Canyon, is also the result of broad tectonic uplift followed by river erosion.
Isostatic uplift includes the gradual uplift following rapid erosional removal of material from a mountain range. The land rises as a result of the removal of the weight. Another example of isostatic uplift is post-glacial rebound following the melting of continental glaciers and ice sheets. The Hudson Bay region of Canada and the Great Lakes of Canada and the United States are currently undergoing gradual rebound as a result of the melting of the ice sheets 10,000 years ago.
In a few cases, tectonic uplift can be seen in the cases of coral islands. This is evidenced by the presence of various oceanic islands comprised entirely of coral, which otherwise appear to be high islands (i.e., islands of volcanic origin). Examples of such islands are found in the Pacific, notably the three great phosphate rocks, Nauru, Makatea, and Banaba as well as Fatu Huku in the Marquesas Islands and Henderson Island in the Pitcairn Islands. The uplift of these islands is the result of the movement of oceanic tectonic plates. Sunken islands or guyots with their coral reefs are the result of crustal subsidence as the oceanic plate carries the islands to deeper or lower oceanic crust areas.
Join NASA in celebrating Sun-Earth Day on March 20
Sun-Earth Day is comprised of a series of programs and events that
occur throughout the year culminating with a celebration on or near the
Spring Equinox. For Sun-Earth Day 2009, NASA will engage a worldwide
audience in the celebration of the International Year of Astronomy,
with an emphasis on daytime astronomy. Tremendous strides have been
made as satellites and ground-based observatories attentively monitor
the sun to understand the processes that govern the sun's influence on
the solar system. NASA will offer a series of coordinated events to
promote and highlight the sun and its connection to Earth and other
planets. The events will support the spirit of international
collaboration.
Over the past eight years, the
NASA Sun-Earth Connection Education Forum has sponsored and coordinated
education and public outreach events to highlight NASA Sun-Earth
Connection research and discoveries. The Forum's strategy involves
using celestial events, such as total solar eclipses and the Transit of
Venus, as well as Sun-Earth Day during the March equinox, to engage
K-12 schools and the public in space science activities,
demonstrations, and interactions with space scientists.
Over the past eight years, NASA Sun-Earth Connection Education Forum
has sponsored and coordinated education and public outreach events to
highlight NASA Sun-Earth Connection research and discoveries. Our
strategy involves using celestial events, such as total solar eclipses
and the Transit of Venus, as well as Sun-Earth Day during the March
Equinox, to engage K-12 schools and the general public in space science
activities, demonstrations, and interactions with space scientists.
In collaboration with partners that include science centers and museums
around the world, the Exploratorium, NASA Connect, Sun-Earth Connection
missions, and others, we produce webcasts, other multi-media, and print
resources for use by school and informal educators nation-wide and
internationally. We provide training and professional development to
K-12 educators, museum personnel, amateur astronomers, Girl Scout
leaders, etc., so they can implement their own outreach programs taking
advantage of our resources. A coordinated approach promotes multiple
programs occurring each year under a common theme.
The Indian Air Force was officially established on 8th October 1932,
and on 1st April 1954, Air Marshal Subroto Mukherjee, one of the
founding members of the Air Force took over as the first Indian Chief
of Air Staff. With the passage of time, the Indian Air Force undertook
massive upgrading of its aircraft and equipments, and as part of the
process, it introduced more than twenty new types of aircrafts. The
last decade of the twentieth century saw a phenomenal change in the
structure of the Indian Air Force with induction of women into the Air
Force for short service commissions. It was also a time when the Air
Force undertook some of the most perilous operations ever undertaken.
A plan for a rail system in India was first put forward in 1832, but no further steps were taken for more than a decade. In 1844, the Governor-General of India Lord Hardinge allowed private entrepreneurs to set up a rail system in India. The East India Company (and later the British Government) encouraged new railway companies backed by private investors under a scheme that would provide land and guarantee an annual return of up to five percent during the initial years of operation. The companies were to build and operate the lines under a 99 year lease, with the government having the option to buy them earlier.
Two new railway companies, Great Indian Peninsular Railway (GIPR) and East Indian Railway (EIR), were created in 1853-54 to construct and operate two 'experimental' lines near Bombay and Calcutta respectively. The first train in India had become operational on 22 December 1851 for localised hauling of canal construction material in Roorkee. A year and a half later, on 16 April 1853, the first passenger train service was inaugurated between Bori Bunder in Bombay and Thane. Covering a distance of 34 kilometres (21 mi), it was hauled by three locomotives, Sahib, Sindh, and Sultan.
In 1854 Lord Dalhousie, the then Governor-General of India, formulated a plan to construct a network of trunk lines connecting the principal regions of India. Encouraged by the government guarantees, investment flowed in and a series of new rail companies were established, leading to rapid expansion of the rail system in India. Soon various native states built their own rail systems and the network spread to the regions that became the modern-day states of Assam, Rajasthan and Andhra Pradesh. The route mileage of this network increased from 1,349 kilometres (838 mi) in 1860 to 25,495 kilometres (15,842 mi) in 1880 - mostly radiating inland from the three major port cities of Bombay, Madras, and Calcutta. Most of the railway construction was done by Indian companies. The railway line from Lahore to Delhi was done B.S.D. Bedi and Sons (Baba Shib Dayal Bedi), this included the building of the Jamuna Bridge. By 1895, India had started building its own locomotives, and in 1896 sent engineers and locomotives to help build the Uganda Railway.
At the beginning of the twentieth century India had a multitude of rail services with diverse ownership and management, operating on broad, metre and narrow gauge networks. In 1900 the government took over the GIPR network, while the company continued to manage it. With the arrival of the First World War, the railways were used to transport troops and foodgrains to the port city of Bombay and Karachi en route to UK, Mesopotamia, East Africa etc. By the end of the First World War, the railways had suffered immensely and were in a poor state. In 1923, both GIPR and EIR were nationalized with the state assuming both ownership and management control.
The Second World War severely crippled the railways as rolling stock was diverted to the Middle East, and the railway workshops were converted into munitions workshops. At the time of independence in 1947, about 40 per cent of the railways then went to newly-created nation of Pakistan.A total of forty-two separate railway systems, including thirty-two lines owned by the former Indian princely states, were amalgamated as a single unit which was christened as the Indian Railways. The existing rail networks were abandoned in favour of zones in 1951 and a total of six zones came into being in 1952.
As the economy of India improved, almost all railway production units were 'indigenised' . By 1985, steam locomotives were phased out in favour of diesel and electric locomotives. The entire railway reservation system was streamlined with computerisation between 1987 and 1995.
The vast majority of the world's glaciers are retreating as the planet gets warmer. But a few, including glaciers south of the equator in South America and New Zealand, are inching forward.
A paper in this week's issue of the journal Science puts this enigma in perspective; for the last 7,000 years, New Zealand's largest glaciers have often moved out of step with glaciers in the Northern Hemisphere, pointing to strong regional variations in climate.
"This research should provide much more accurate reconstructions of glacial advances worldwide, allowing us in turn to make climate models more accurate," said Paul Filmer, program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research.
Conventional wisdom holds that during the era of human civilization, climate has been relatively stable. The new study is the latest to challenge this view, by showing that New Zealand's glaciers have gone through rapid periods of growth and decline during the current interglacial period known as the Holocene.
"New Zealand's mountain glaciers have fluctuated frequently over the last 7,000 years, and glacial advances have become slightly smaller through time," said Joerg Schaefer, lead author of the paper and a geochemist at Columbia University's Lamont-Doherty Earth Observatory.
"This pattern differs in important ways from the northern hemisphere glaciers. The door is open now towards a global map of Holocene [a geological time period that began about 11,700 years ago and continues to the present] glacier fluctuations and how climate variations during this period impacted human civilizations."
Glaciers are extremely sensitive to changes in temperature and snowfall, which makes them well suited for studying past climate. This archive has been largely untapped, however, because of the difficulty in assigning precise ages to glacier fluctuations.
One way to measure glacial fluxes is by studying the moraines, or rock deposits that glaciers often leave behind at their maximum points of advance.
However, until now the methods of dating such moraines, including radiocarbon dating of organic matter, could be off by hundreds of years.
By refining the analysis of a method called cosmogenic dating, Schaefer and colleagues were able for the first time to assign precise ages to young Holocene moraines.
They accomplished this by measuring minute levels of the chemical isotope beryllium 10 in the rocks, which is produced when cosmic rays strike rock surfaces, and builds up over time.
The researchers were thus able to pinpoint exactly when glaciers in New Zealand's Southern Alps began to recede, exposing the rocks to the cosmic rays.
From the results, they constructed a glacial timeline for the past 7,000 years and compared it against historic records from the Swiss Alps and other places north of the equator.
They found that within that timeframe, the glaciers around Mount Cook, New Zealand's highest peak, reached their largest extent about 6,500 years ago, when the Swiss Alps and Scandinavia were relatively warm.
That's about 6,000 years before northern glaciers hit their Holocene peak during the Little Ice Age, between 1300 and 1860 AD.
That finding was a surprise to some scientists who assumed that the northern cold phase happened globally. The record in New Zealand shows other disparities that point to regional climate variations in both hemispheres.
The new chemical and analytical protocols are expected to allow scientists to accurately date glacier fluctuations throughout the Holocene, rounding out the climate picture on the continents.
"With this measure we can go to almost any mountain range on earth and date the moraines in front of the glaciers and produce a similar chronology," said co-author George Denton, a glaciologist at the University of Maine and an adjunct scientist at Lamont-Doherty.
Overall, glaciers around the world have been declining since about 1860, with the exception of a brief advance in Switzerland in the 1980s, New Zealand in the late 1970s through today, and a few other places.
Changes in wind and sea surface temperatures are thought to be causing these regional fluctuations.
Currently in a wet phase, New Zealand is expected to swing back to a warmer, drier phase in the next few years, causing the glaciers to retreat once again.
The study also received funding from the Comer Science and Education Foundation, and the New Zealand Foundation for Research, Science and Technology.
Other researchers involved in the study were: Michael Kaplan and Roseanne Schwartz, also of Lamont-Doherty; Aaron Putnam, University of Maine; Robert Finkel, CEREGE, France; David Barrell, GNS Science, New Zealand; Bjorn Anderson, University of Oslo; Andrew Mackintosh, Victoria University of Wellington, New Zealand; Trevor Chinn, Alpine and Polar Processes Consultancy, New Zealand; Christian Schluchter, University of Bern, Switzerland.
