rajpurkar/squad huggingface dataset:
Title: Film_speed

Based on earlier research work by Loyd Ancile Jones (1884–1954) of Kodak and inspired by the systems of Weston film speed ratings and General Electric film values, the American Standards Association (now named ANSI) defined a new method to determine and specify film speeds of black-and-white negative films in 1943. ASA Z38.2.1-1943 was revised in 1946 and 1947 before the standard grew into ASA PH2.5-1954. Originally, ASA values were frequently referred to as American standard speed numbers or ASA exposure-index numbers. (See also: Exposure Index (EI).)

Question: Who pioneered research that led to the new ANSI values?
Answer: Loyd Ancile Jones

Question: What standards were the ANSI developed from?
Answer: Weston film speed ratings and General Electric film values

Question: What types of film did the ANSI measure?
Answer: black-and-white negative films

Question: When did the ANSI define its new measure?
Answer: 1943

Question: What were ANSI values often called in the beginning?
Answer: American standard speed numbers or ASA exposure-index numbers
Title: Film_speed

The ASA standard underwent a major revision in 1960 with ASA PH2.5-1960, when the method to determine film speed was refined and previously applied safety factors against under-exposure were abandoned, effectively doubling the nominal speed of many black-and-white negative films. For example, an Ilford HP3 that had been rated at 200 ASA before 1960 was labeled 400 ASA afterwards without any change to the emulsion. Similar changes were applied to the DIN system with DIN 4512:1961-10 and the BS system with BS 1380:1963 in the following years.

Question: In what year were big changes made to the ANSI?
Answer: 1960

Question: What did the 1960 changes to film speed measures lead to?
Answer: effectively doubling the nominal speed of many black-and-white negative films

Question: Which other system were these changes applied to?
Answer: the DIN system

Question: In what year was the BS system modified?
Answer: 1963

Question: What safety factors were done away with beginning with the modifications to the standards?
Answer: safety factors against under-exposure
Title: Film_speed

Film speed is found from a plot of optical density vs. log of exposure for the film, known as the D–log H curve or Hurter–Driffield curve. There typically are five regions in the curve: the base + fog, the toe, the linear region, the shoulder, and the overexposed region. For black-and-white negative film, the “speed point” m is the point on the curve where density exceeds the base + fog density by 0.1 when the negative is developed so that a point n where the log of exposure is 1.3 units greater than the exposure at point m has a density 0.8 greater than the density at point m. The exposure Hm, in lux-s, is that for point m when the specified contrast condition is satisfied. The ISO arithmetic speed is determined from:

Question: What is the plot from which film speed is derived called?
Answer: the D–log H curve or Hurter–Driffield curve

Question: How many regions does the Hurter-Driffield curve have?
Answer: five

Question: What is plotted in the Hurter-Driffield curve?
Answer: a plot of optical density vs. log of exposure for the film

Question: What is denoted when the specified contrast condition is met?
Answer: The exposure Hm, in lux-s

Question: What are the five regions of the Hurter-Driffield curve?
Answer: the base + fog, the toe, the linear region, the shoulder, and the overexposed region
Title: Film_speed

Film speed is used in the exposure equations to find the appropriate exposure parameters. Four variables are available to the photographer to obtain the desired effect: lighting, film speed, f-number (aperture size), and shutter speed (exposure time). The equation may be expressed as ratios, or, by taking the logarithm (base 2) of both sides, by addition, using the APEX system, in which every increment of 1 is a doubling of exposure; this increment is commonly known as a "stop". The effective f-number is proportional to the ratio between the lens focal length and aperture diameter, the diameter itself being proportional to the square root of the aperture area. Thus, a lens set to f/1.4 allows twice as much light to strike the focal plane as a lens set to f/2. Therefore, each f-number factor of the square root of two (approximately 1.4) is also a stop, so lenses are typically marked in that progression: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc.

Question: What is the effective f-number proportional to?
Answer: the ratio between the lens focal length and aperture diameter

Question: What is used to discover the right exposure parameters?
Answer: Film speed

Question: What variables help the photographer produce the desired effect?
Answer: lighting, film speed, f-number (aperture size), and shutter speed (exposure time)

Question: A lens with a setting of f/1.4 lets how much to hit the focal plane compared with a setting of f/2?
Answer: twice as much

Question: In the APEX system, the increment that doubles the exposure is called what?
Answer: "stop"
Title: Film_speed

Upon exposure, the amount of light energy that reaches the film determines the effect upon the emulsion. If the brightness of the light is multiplied by a factor and the exposure of the film decreased by the same factor by varying the camera's shutter speed and aperture, so that the energy received is the same, the film will be developed to the same density. This rule is called reciprocity. The systems for determining the sensitivity for an emulsion are possible because reciprocity holds. In practice, reciprocity works reasonably well for normal photographic films for the range of exposures between 1/1000 second to 1/2 second. However, this relationship breaks down outside these limits, a phenomenon known as reciprocity failure.

Question: What determines the effect on the emulsion after exposure?
Answer: the amount of light energy that reaches the film

Question: In what range of exposures does reciprocity usually work?
Answer: between 1/1000 second to 1/2 second

Question: How is the exposure of film changed?
Answer: by varying the camera's shutter speed and aperture

Question: How are ways of finding an emulsion's sensitivity possible?
Answer: because reciprocity holds

Question: What happens outside the 1/1000 second to 1/second exposure range?
Answer: reciprocity failure
Title: Film_speed

Some high-speed black-and-white films, such as Ilford Delta 3200 and Kodak T-MAX P3200, are marketed with film speeds in excess of their true ISO speed as determined using the ISO testing method. For example, the Ilford product is actually an ISO 1000 film, according to its data sheet. The manufacturers do not indicate that the 3200 number is an ISO rating on their packaging. Kodak and Fuji also marketed E6 films designed for pushing (hence the "P" prefix), such as Ektachrome P800/1600 and Fujichrome P1600, both with a base speed of ISO 400.

Question: What are two examples of films that are marketed with speeds above their true ISO speed?
Answer: Ilford Delta 3200 and Kodak T-MAX P3200

Question: What speed of film is the Ilford Delta 3200?
Answer: ISO 1000

Question: Which two companies produced E6 films meant for "pushing"?
Answer: Kodak and Fuji

Question: What is the base speed of Ektachrome P800/1600 and Fujichrome P1600?
Answer: ISO 400

Question: What type of films are Ilford Delta 3200 and Kodak T-MAX P3200?
Answer: high-speed black-and-white films
Title: Film_speed

For digital photo cameras ("digital still cameras"), an exposure index (EI) rating—commonly called ISO setting—is specified by the manufacturer such that the sRGB image files produced by the camera will have a lightness similar to what would be obtained with film of the same EI rating at the same exposure. The usual design is that the camera's parameters for interpreting the sensor data values into sRGB values are fixed, and a number of different EI choices are accommodated by varying the sensor's signal gain in the analog realm, prior to conversion to digital. Some camera designs provide at least some EI choices by adjusting the sensor's signal gain in the digital realm. A few camera designs also provide EI adjustment through a choice of lightness parameters for the interpretation of sensor data values into sRGB; this variation allows different tradeoffs between the range of highlights that can be captured and the amount of noise introduced into the shadow areas of the photo.

Question: What is another name for an exposure index rating?
Answer: ISO setting

Question: How do some camera designs give some EI choices?
Answer: by adjusting the sensor's signal gain in the digital realm

Question: Who provides the exposure index rating?
Answer: the manufacturer

Question: What are digital photo cameras also called?
Answer: digital still cameras
Title: Film_speed

Digital cameras have far surpassed film in terms of sensitivity to light, with ISO equivalent speeds of up to 409,600, a number that is unfathomable in the realm of conventional film photography. Faster processors, as well as advances in software noise reduction techniques allow this type of processing to be executed the moment the photo is captured, allowing photographers to store images that have a higher level of refinement and would have been prohibitively time consuming to process with earlier generations of digital camera hardware.

Question: What types of cameras have proven to be much more sensitive to light than film?
Answer: Digital cameras

Question: What ISO equivalent speeds can digital cameras obtain?
Answer: 409,600

Question: What is responsible for these vast increases in speed?
Answer: Faster processors, as well as advances in software noise reduction techniques

Question: What is one thing that limited speeds of older digital hardware?
Answer: prohibitively time consuming to process

Question: What does the higher speed do for the images produced?
Answer: a higher level of refinement
Title: Film_speed

The ISO standard ISO 12232:2006 gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model. Three of the techniques in ISO 12232:2006 are carried over from the 1998 version of the standard, while two new techniques allowing for measurement of JPEG output files are introduced from CIPA DC-004. Depending on the technique selected, the exposure index rating can depend on the sensor sensitivity, the sensor noise, and the appearance of the resulting image. The standard specifies the measurement of light sensitivity of the entire digital camera system and not of individual components such as digital sensors, although Kodak has reported using a variation to characterize the sensitivity of two of their sensors in 2001.

Question: How many techniques are available because of ISO 12232:2006?
Answer: five

Question: What techniques did CIPA DC-004 provide?
Answer: two new techniques allowing for measurement of JPEG output files

Question: What factors affect the exposure index rating?
Answer: the sensor sensitivity, the sensor noise, and the appearance of the resulting image

Question: What does the standard of ISO 12232:2006 specify?
Answer: the measurement of light sensitivity of the entire digital camera system and not of individual components

Question: In what year did Kodak start using a different way of characterizing two sensors?
Answer: 2001
Title: Film_speed

The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily. The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used.

Question: What option does the Recommended Exposure Index give manufacturers? 
Answer: to specify a camera model’s EI choices arbitrarily

Question: What is another name for multi-zone metering?
Answer: pattern metering

Question: What distinction does the Recommended Exposure Index have?
Answer: the only technique available under the standard for output formats that are not in the sRGB color space

Question: When was the Recommended Exposure Index introduced?
Answer: 2006

Question: What is the only technique that can be used when multi-zone metering is used?
Answer: Recommended Exposure Index (REI) technique
Title: Film_speed

The Standard Output Sensitivity (SOS) technique, also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when the exposure is controlled by an automatic exposure control system calibrated per ISO 2721 and set to the EI with no exposure compensation. Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format. It is not applicable when multi-zone metering is used.

Question: What year was the Standard Output Sensitivity technique introduced?
Answer: 2006

Question: What does the Standard Output Sensitivity technique apply to?
Answer: sRGB images—typically JPEG

Question: What is the output level measured in?
Answer: the sRGB output from the camera

Question: With what type of metering can the Standard Output Sensitivity not be used?
Answer: multi-zone metering

Question: With what standard is the automatic exposure control system calibrated?
Answer: ISO 2721
Title: Film_speed

The CIPA DC-004 standard requires that Japanese manufacturers of digital still cameras use either the REI or SOS techniques, and DC-008 updates the Exif specification to differentiate between these values. Consequently, the three EI techniques carried over from ISO 12232:1998 are not widely used in recent camera models (approximately 2007 and later). As those earlier techniques did not allow for measurement from images produced with lossy compression, they cannot be used at all on cameras that produce images only in JPEG format.

Question: Which methods are required by CIPA DC-004?
Answer: REI or SOS techniques

Question: In what year did the three EI techniques from ISO 12232:1998 largely stop being used?
Answer: approximately 2007 and later

Question: With what cameras can earlier techniques not be used?
Answer: cameras that produce images only in JPEG format

Question: What nation's cameras does the CIPA DC-004 apply to?
Answer: Japanese

Question: What does the DC-008 change?
Answer: the Exif specification
Title: Film_speed

where  is the maximum possible exposure that does not lead to a clipped or bloomed camera output. Typically, the lower limit of the saturation speed is determined by the sensor itself, but with the gain of the amplifier between the sensor and the analog-to-digital converter, the saturation speed can be increased. The factor 78 is chosen such that exposure settings based on a standard light meter and an 18-percent reflective surface will result in an image with a grey level of 18%/√2 = 12.7% of saturation. The factor √2 indicates that there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface.

Question: What does the sensor usually determine?
Answer: lower limit of the saturation speed

Question: How can the saturation speed be increased?
Answer: with the gain of the amplifier between the sensor and the analog-to-digital converter

Question: What is indicated by the factor √2?
Answer: there is half a stop of headroom to deal with specular reflections that would appear brighter than a 100% reflecting white surface

Question: What can too much exposure lead to?
Answer: clipped or bloomed camera output
Title: Film_speed

The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels. Two ratios are used, the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio. These ratios have been subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance. The signal-to-noise ratio is defined as the standard deviation of a weighted average of the luminance and color of individual pixels. The noise-based speed is mostly determined by the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter.

Question: Which ratios are employed to calculate noise-based speed?
Answer: the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio

Question: What is the noise-based speed?
Answer: the exposure that will lead to a given signal-to-noise ratio on individual pixels

Question: How are the two ratios found?
Answer: subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance

Question: What is a definition of signal-to-noise ratio?
Answer: the standard deviation of a weighted average of the luminance and color of individual pixels

Question: What factors influence the noise-based speed?
Answer: the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter
Title: Film_speed

The standard specifies how speed ratings should be reported by the camera. If the noise-based speed (40:1) is higher than the saturation-based speed, the noise-based speed should be reported, rounded downwards to a standard value (e.g. 200, 250, 320, or 400). The rationale is that exposure according to the lower saturation-based speed would not result in a visibly better image. In addition, an exposure latitude can be specified, ranging from the saturation-based speed to the 10:1 noise-based speed. If the noise-based speed (40:1) is lower than the saturation-based speed, or undefined because of high noise, the saturation-based speed is specified, rounded upwards to a standard value, because using the noise-based speed would lead to overexposed images. The camera may also report the SOS-based speed (explicitly as being an SOS speed), rounded to the nearest standard speed rating.

Question: What is the range for exposure latitude?
Answer: from the saturation-based speed to the 10:1 noise-based speed

Question: What is another speed that can also be reported by the camera?
Answer: SOS-based speed

Question: When should the noise-based speed be used?
Answer: the noise-based speed (40:1) is higher than the saturation-based speed

Question: Why should noise-based speed be rounded down to a lower standard?
Answer: exposure according to the lower saturation-based speed would not result in a visibly better image

Question: What does the standard specify?
Answer: how speed ratings should be reported by the camera
Title: Film_speed

Despite these detailed standard definitions, cameras typically do not clearly indicate whether the user "ISO" setting refers to the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes. Because the 1998 version of ISO 12232 did not permit measurement of camera output that had lossy compression, it was not possible to correctly apply any of those measurements to cameras that did not produce sRGB files in an uncompressed format such as TIFF. Following the publication of CIPA DC-004 in 2006, Japanese manufacturers of digital still cameras are required to specify whether a sensitivity rating is REI or SOS.[citation needed]

Question: What measures might the user "ISO" setting correspond to?
Answer: the noise-based speed, saturation-based speed, or the specified output sensitivity, or even some made-up number for marketing purposes

Question: What did the 1998 version of ISO 12232 not permit?
Answer: measurement of camera output that had lossy compression

Question: What types of sensitivity ratings can be specified by a camera?
Answer: REI or SOS

Question: What standards changed what Japanese camera makers have to specify?
Answer: CIPA DC-004

Question: In what year was CIPA DC-004 introduced?
Answer: 2006
Title: Mexico_City

Mexico City, or the City of Mexico (Spanish: Ciudad de México  audio (help·info) American Spanish: [sjuˈða(ð) ðe ˈméxiko]; abbreviated as "CDMX"), is the capital of Mexico. As an "alpha" global city, Mexico City is one of the most important financial centers in the Americas. It is located in the Valley of Mexico (Valle de México), a large valley in the high plateaus at the center of Mexico, at an altitude of 2,240 metres (7,350 ft). The city consists of sixteen municipalities (previously called boroughs).

Question: How man feet above sea level is Mexico City
Answer: 7,350

Question: How many municipalities are in Mexico City?
Answer: sixteen

Question: What did they used to call the municipalities within Mexico City?
Answer: boroughs

Question: What is the Spanish word for Mexico City?
Answer: Ciudad de México

Question: How many meters above sea is Mexico City?
Answer: 2,240
Title: Mexico_City

The Greater Mexico City has a gross domestic product (GDP) of US$411 billion in 2011, making Mexico City urban agglomeration one of the economically largest metropolitan areas in the world. The city was responsible for generating 15.8% of Mexico's Gross Domestic Product and the metropolitan area accounted for about 22% of total national GDP. As a stand-alone country, in 2013, Mexico City would be the fifth-largest economy in Latin America—five times as large as Costa Rica's and about the same size as Peru's.

Question: How big is Mexico City's GDP?
Answer: US$411 billion

Question: How much bigger is Mexico City's GDP's than Costa Rica's?
Answer: five times

Question: What percent of the Mexican GDP is the metropolitan area of Mexico City responsible for?
Answer: 22%

Question: Which country has about the same size GDP as Mexico city?
Answer: Peru
Title: Mexico_City

Mexico’s capital is both the oldest capital city in the Americas and one of two founded by Amerindians (Native Americans), the other being Quito. The city was originally built on an island of Lake Texcoco by the Aztecs in 1325 as Tenochtitlan, which was almost completely destroyed in the 1521 siege of Tenochtitlan, and subsequently redesigned and rebuilt in accordance with the Spanish urban standards. In 1524, the municipality of Mexico City was established, known as México Tenochtitlán, and as of 1585 it was officially known as Ciudad de México (Mexico City). Mexico City served as the political, administrative and financial center of a major part of the Spanish colonial empire. After independence from Spain was achieved, the Federal District was created in 1824.

Question: What was the original name of Mexico City?
Answer: Tenochtitlan

Question: Who originally built Mexico City?
Answer: the Aztecs

Question: When was the Federal District formed?
Answer: 1824

Question: Where was the city first built?
Answer: on an island of Lake Texcoco

Question: When was Mexico City officially founded by the Spanish?
Answer: 1585