Problem: 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.
How much does light does an f/2 let in as compared to an f/4?
---
Answer: unanswerable

Problem: There are various terms that linguists may use to avoid taking a position on whether the speech of a community is an independent language in its own right or a dialect of another language. Perhaps the most common is "variety"; "lect" is another. A more general term is "languoid", which does not distinguish between dialects, languages, and groups of languages, whether genealogically related or not.
Which is the most uncommon term linguists use to avoid taking a position on the speech of a community?
---
Answer: unanswerable

Problem: Roman histories and biographies anticipated the extensive mediaeval literature of lives of saints and miraculous chronicles, but the most characteristic form of the Middle Ages was the romance, an adventurous and sometimes magical narrative with strong popular appeal. Controversial, religious, political and instructional literature proliferated during the Renaissance as a result of the invention of printing, while the mediaeval romance developed into a more character-based and psychological form of narrative, the novel, of which early and important examples are the Chinese Monkey and the German Faust books.
What is an early example of the novel form of literature from Europe?
---
Answer:
the German Faust books