| 单词 | focal length |
| 例句 | One specialized jet could film the same scene using two different lens focal lengths to double the footage captured on a single flight. Winning the Skies Without Losing Your Lunch: Filming ‘Top Gun: Maverick’ 2022-05-27T04:00:00Z The lens was so heavy that he had to screw it into his tripod, and when he aimed at a wall in his apartment, the distance was too short for the focal length. Were These Photographs Voyeurism, or Art? 2023-03-03T05:00:00Z In the '60s, movie directors fell in love with the zoom lens, and for a while no movie image was hip unless it changed focal lengths every few seconds. Battle Los Angeles: A Shaky, Breaky Mess 2011-03-11T11:05:00Z "They have a fixed focal length, a fixed size. They are made from materials that give you the lensing property you want, but they don't really have any dynamic characteristics." Chemists, engineers craft adjustable arrays of microscopic lenses 2023-10-23T04:00:00Z The museum includes a camera the C.I.A. built for Mr. Tolkachev, with a fixed focal length to ensure his pictures would be less blurry. Two Renovated Museums Offer a Peek at Spy Secrets — at Least for Some 2022-09-24T04:00:00Z This also allows Apple to crop the sensor in different ways to deliver true 2x zoom at a 48mm focal length. Hands-on with the iPhone 14 Pro and iPhone 14 Pro Max 2022-09-07T04:00:00Z Real images, such as the one considered in the previous example, are formed by converging lenses whenever an object is farther from the lens than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z The lens is operated by muscles that stretch it flat or allow it to thicken, changing the focal length of light coming through it to focus it sharply on the retina. Biology for AP Courses 2022-06-09T00:00:00Z In the case of parallel light rays, the distance from the lens to the location where the light rays focus, or image, behind the lens is called the focal length of the lens. Astronomy 2016-10-13T00:00:00Z The focal length is tight but the minimum focusing distance is long, meaning it’s not useful for taking photos of close objects. The Duovox Mate Pro is a tiny camera that truly sees in the dark 2022-04-13T04:00:00Z If your camera has an interchangeable lens, bring several lenses of varying focal lengths: macro, wide angle and telephoto. How to take Instagram-worthy travel photos 2022-02-24T05:00:00Z Figure 25.36 Ray tracing predicts the image location and size for an object held closer to a converging lens than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z I know how much more flattering a longer focal length would be than my MacBook Air’s built-in wide-angle lens. I refuse to care about the quality of my webcam 2021-12-30T05:00:00Z A detachable lens system not only allows for much more flexibility in image quality and focal length but also gets a whole community of prosumers buying more accessories. Sony Alpha ZV-E10 review: interchangeable lens vlogging machine 2021-10-06T04:00:00Z The XPan Mode replicates the focal lengths, colors, and processing of the original XPan camera for the phone, allowing you to capture wide aspect ratio images from your phone. OnePlus 9 update brings the Hasselblad XPan camera aesthetics to mobile 2021-09-17T04:00:00Z The telephoto camera remains exclusive to the 13 Pro phones, and Apple has increased its equivalent focal length to 77mm, or three times longer than the primary camera. Apple says it every year, but the iPhone 13 cameras do seem much improved 2021-09-15T04:00:00Z This is a case 3 image, formed for any object by a negative focal length or diverging lens. College Physics for AP Courses 2015-08-12T00:00:00Z The basic mode is refreshingly minimal — there are quick shortcuts to different focal lengths, to turn bokeh mode on or off, enable continuous shooting, and access flash settings, but not much more than that. Sony’s Xperia 1 III is pricey, performant, and perplexing 2021-07-17T04:00:00Z The “focal length” difference between the two is almost laughably small. Samsung Galaxy A52 5G review: a midrange phone that will last 2021-04-24T04:00:00Z Grid View There’s the focal length I mentioned earlier, but also the dynamic range on the 2 Pro is better. The Mavic Air 2S has the same size camera as the 2 Pro 2021-04-15T04:00:00Z As its name implies, the lens typically includes a layer of liquid, and the lens’s focus and focal length are changed by applying an electrical voltage. Xiaomi teases camera with liquid lens on upcoming Mi Mix 2021-03-25T04:00:00Z Now let us consider the focal length of a mirror—for example, the concave spherical mirrors in Figure 25.40. College Physics for AP Courses 2015-08-12T00:00:00Z To re-create these images, Matt flew to each location, then used Flight Simulator to position the camera, set the focal length, and adjust the time of day with in-game controls. Microsoft Flight Simulator’s re-creations of macOS wallpapers look just as good 2020-08-31T04:00:00Z Periscope cameras are a way of enabling long focal lengths in devices like smartphones where physical depth is at a premium. iPhones to get periscope telephoto cameras in 2022, says Kuo 2020-07-22T04:00:00Z If you do the math on those focal lengths, it all adds up to a little more than 5x optical “zoom”, with software filling in the gaps between each lens. Oppo unveils quad-camera Reno 2 range of phones 2019-08-28T04:00:00Z It also doesn’t work as well at all focal lengths. Moment is making an anamorphic lens for DJI drones 2019-07-09T04:00:00Z Since this mirror is converging, it has a positive focal length. College Physics for AP Courses 2015-08-12T00:00:00Z Regular camera: It’s your basic, everyday camera with a focal length appropriate for a wide variety of situations. Samsung’s Galaxy S10 has up to six cameras: here’s what they all do 2019-02-20T05:00:00Z The ultra wide lens, equivalent to a 16mm focal length, will come in handy for group photos, landscapes, and when you’re up close to something big and want to capture its entirety. Huawei Mate 20 Pro review: the best phone America can’t get 2018-10-24T04:00:00Z Here’s how it works: the Zoom takes a total of nine photos, the first one being a reference file at the wider 24mm focal length. DJI’s Mavic 2 Pro and Zoom take drone photography to new heights 2018-09-06T04:00:00Z There was an F-mount adapter available, but the sensor size meant that focal lengths were cropped to extreme degrees, turning all but the widest lenses into telephotos. Nikon announces full-frame mirrorless camera system under development 2018-07-25T04:00:00Z A more strongly curved mirror has a shorter focal length and a greater power. College Physics for AP Courses 2015-08-12T00:00:00Z The L16 might save all the space that a zoom lens takes up, but smaller isn’t always better at long focal lengths. Light L16 camera review: futuristic frustration 2018-04-10T04:00:00Z Cars are also ideally suited to the fixed wide-angle view of a phone camera: I wanted to be shooting at that focal length anyway. The Pixel 2 XL was my only camera at the Geneva Motor Show 2018-03-09T05:00:00Z Extension tubes, which are generally used for close-up photography, increase the focal length of a lens. How a Student Took a Photo of a Single Atom 2018-02-14T05:00:00Z The longer the lens's focal length, the larger the sun will be in the final image. How to Photograph the Solar Eclipse 2017-08-08T04:00:00Z Convex mirrors diverge light rays and, thus, have a negative focal length. College Physics for AP Courses 2015-08-12T00:00:00Z One of the best aspects of this camera is definitely its wide lens, with a 38mm focal length and maximum aperture of f/4.5. The Best Instant Film Cameras You Can Buy Right Now 2017-06-15T04:00:00Z The emission was collected in magic angle configuration using two 1-inch diameter, 50 mm focal length quartz lenses and focused on the spectrograph coupled to a Hamamatsu streak camera C6860 device. A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence : Nature : Nature Research 2017-03-28T04:00:00Z The camera uses four lenses instead of one, each set at different focal lengths and mounted on an image-reading microchip that compiles data from all four lenses into a single image. These tiny camera lenses can ‘see’ like an eagle 2017-02-15T05:00:00Z It's easier to get up close when the lens is at its default focal length. Hasselblad's new $250 MotoMod adds 10x optical zoom to the Moto Z 2016-08-31T04:00:00Z Power P of a lens is defined to be the inverse of its focal length, P = 1 . College Physics for AP Courses 2015-08-12T00:00:00Z Billed by the owner as "the world's largest camera", it looks almost comically enlarged - even by vintage standards - and sits on an iron slider used to adjust focal length. Columbia's cinema museum: 'Where the magic begins:' - BBC News 2016-05-27T04:00:00Z It clicks into place over the handset's built-in camera lens, changing the angle and focal length of the picture that the phone takes. The man who bet his house on his mobile phone invention - BBC News 2016-04-24T04:00:00Z For years, consumers have been more than satisfied with the default focal length of iPhones and Android handsets. Asus ZenFone Zoom: do you really need a zoom lens in your smartphone? 2016-02-04T05:00:00Z The idea is that one camera would have a wide lens, and the other would have a much deeper focal length. Apple has thought about putting two rear cameras on the iPhone 2016-01-07T05:00:00Z Will the focal length of a lens change when it is submerged in water? College Physics for AP Courses 2015-08-12T00:00:00Z Behind each of those plastic lenses is a 13-megapixel camera module, each grouped into three different focal lengths. This camera is actually 16 cameras in one 2015-10-07T04:00:00Z When you shoot at such an extended focal length, there’s a great deal more compression between the middle and far distances. Shadows in São Paulo 2015-08-19T04:00:00Z It is actually a double exposure that uses a zoom lens to emphasise the sun, and then a shorter focal length lens and flash to pick up the colours in the stinging arthropod. Slumbering lions win top photo prize 2014-10-21T04:00:00Z Metadata can be extremely useful to photographers; nearly all metadata includes information like the focal length used to take the photo and the photo's exposure. How Someone Can Track You With a Photograph You Took It can be argued that a flat mirror has an infinite focal length. College Physics for AP Courses 2015-08-12T00:00:00Z With either lens you get a genuinely useful focal length and sacrifice nothing in image quality. Moment Brings High-End Camera Lenses To Your iPhone 2014-08-30T04:00:00Z Just when the camera was poised, the focal length set, and THD bent lightly from the waist, up walked an American woman who inquired, in a fluty voice, “What ever are you doing?’ Lake Como's Billionaire-View Suites At The Grand Hotel Tremezzo 2014-07-10T04:00:00Z "Snapping photos with the iPhone is easy and quick — I don’t need to spend much time struggling with focal length, white balance, and exposure time," says Liu. The best iPhone photos of the year 2014-06-12T04:00:00Z At about age 40, natural changes in the eye’s focal length means most people can’t see closely as well. How bad for your eyes are computer screens? 2014-01-20T21:06:01Z You note that your prescription for new eyeglasses is –4.50 D. What will their focal length be? College Physics for AP Courses 2015-08-12T00:00:00Z You might want to consider using a lens with a long focal length and a wide-open aperture. 10 steps to take a reasonably decent photo of a new baby 2013-08-20T12:32:33Z Look for manufacturer specifications under “focal length” for the “35mm equivalent.” In the Picture: Digital Camera Buying Guide 2013-03-28T09:05:00Z I mention full frame sensor because on many digital cameras the sensor is small, which changes the focal length of the lens, usually by a factor of 1.6. What's wrong with my zoom lens? 2012-12-11T15:13:33Z Because it is this small, its focal length is only 18 metres. The search for alien life: Twinkle, twinkle, little planet 2012-06-07T15:06:09Z A camera with a 100 mm focal length lens is used to photograph the sun and moon. College Physics for AP Courses 2015-08-12T00:00:00Z This was applied to an excellent achromatic telescope of 3� in. aperture and 42 in. focal length. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z He experimented in physical optics; took up astronomy in 1816; and in 1820, assisted by his father, he completed for a reflecting telescope a mirror of 18 in. diameter and 20 ft. focal length. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 4 "Hero" to "Hindu Chronology" 2012-04-04T02:00:56.447Z The eyepiece will usually be made of two lenses, or more, and we use its focal length considered as a single lens, in getting the magnifying power. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z Figure 11.—Zenith sector with focal length of 6 ft., made by David Rittenhouse and revised by Andrew Ellicott. Early American Scientific Instruments and Their Makers 2012-03-15T02:00:31.610Z Use the law of reflection to prove that the focal length of a mirror is half its radius of curvature. College Physics for AP Courses 2015-08-12T00:00:00Z The amount of separation is very small, and depends on the thickness of the glass, the index of refraction and the focal length of the telescope. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z In 1641 he built an observatory in his house, provided with a splendid instrumental outfit, including ultimately a tubeless telescope of 150 ft. focal length, constructed by himself. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 4 "Hero" to "Hindu Chronology" 2012-04-04T02:00:56.447Z The finished mirror is 73 inches in diameter, its focal length is 30 feet, and its thickness 12 inches. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z Made of brass, with focal length of 6 ft. and an aperture of 2-1/2 in. Early American Scientific Instruments and Their Makers 2012-03-15T02:00:31.610Z The object is slightly farther away from the objective lens than its focal length fo , producing a case 1 image that is larger than the object. College Physics for AP Courses 2015-08-12T00:00:00Z The object-glass is of 6 in. aperture and 98 in. focal length. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z Hitherto we have said nothing about the great reflecting telescope, of 40 ft. focal length and 4 ft. aperture, the construction of which is often, though mistakenly, regarded as his chief performance. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 4 "Hero" to "Hindu Chronology" 2012-04-04T02:00:56.447Z A telescope will generally have many eyepieces of different focal lengths, so that it will have a corresponding range of magnifying powers. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z Grazing-incidence optics means that a long focal length is needed — and, conventionally, a bulky, costly spacecraft. Spacecraft aims to expose violent hearts of galaxies 2012-03-14T18:20:21.050Z The eyepiece is placed so that the first image is closer to it than its focal length fe . College Physics for AP Courses 2015-08-12T00:00:00Z The width of each of the portions aghc and acfe cut away from the lens was made slightly greater than the focal length of lens � tangent of sun’s greatest diameter. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z In 1821-1823 we find him associated with Sir James South in the re-examination of his father’s double stars, by the aid of two excellent refractors, of 7 and 5 ft. focal length respectively. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 4 "Hero" to "Hindu Chronology" 2012-04-04T02:00:56.447Z Accordingly, successive steps have led through spectrographs of 18 and 30 feet dimension to a vertical spectrograph 75 feet in focal length. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z Grazing-incidence optics means that a long focal length is needed -- and, conventionally, a bulky, costly spacecraft. Spacecraft Aims to Expose Violent Hearts of Galaxies 2012-03-13T19:45:00.480Z This is because objective lenses are made of a combination of lenses and the focal length is measured from inside the barrel. College Physics for AP Courses 2015-08-12T00:00:00Z Here, in order to fulfil the purposes of the previous models, the distance of the centres of the lenses from each other should only slightly exceed the tangent of sun’s diameter � focal length of lenses. Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2 "Hearing" to "Helmond" 2012-04-25T02:00:53.567Z It is fifteen inches in diameter, and about twenty-three feet focal length; the image it gives of the moon varies but little from three inches, and the prepared plate had an exposure of thirteen seconds.” The Evolution of Photography With a Chronological Record of Discoveries, Inventions, etc., Contributions to Photographic Literature, and Personal Reminescences Extending over Forty Years 2012-02-15T03:00:30.577Z For many months most of the observations and photographs have been made with the Cassegrain combination of mirrors, giving an equivalent focal length of 134 feet and involving three reflections of light. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z These lenses were placed in front of the pictures at a distance equal to twice their focal length. Heroes of Science: Physicists 2012-01-17T03:00:17Z The distance from the center of the lens to its focal point is defined to be the focal length f of the lens. College Physics for AP Courses 2015-08-12T00:00:00Z In this case it is said that the lens having a focal length of one inch magnifies ten times, or has a power of ten. Through a Microscope Something of the Science Together with many Curious Observations Indoor and Out and Directions for a Home-made Microscope. 2011-12-29T03:00:20.733Z Fresnel lenses—originally designed for lighthouses—are flat and thin, and allow for a large aperture and a short focal length. Computerized Contact Lenses Could Enable In-Eye Augmented Reality 2011-11-23T14:15:08.380Z The early makers and users of telescopes in the latter part of the seventeenth century found that the troublesome effects of chromatic aberration could be much reduced by increasing the focal length of the objective. Astronomy: The Science of the Heavenly Bodies 2012-03-17T02:01:02.630Z Humans and animals instinctively extract key features from a blurry image, use that information to determine their distance from an object, then instantly focus the eye to the precise desired focal length, Geisler explains. Deciphering the Brain's Autofocus Mechanism 2011-10-07T20:58:04Z The distance from the center of the lens to the focal point is the lens’s focal length f . College Physics for AP Courses 2015-08-12T00:00:00Z The zenith telescope is made in various sizes from 30 to 54 in. in focal length; a 30-in. telescope is sufficient for the highest purposes and is very portable. Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 6 "Geodesy" to "Geometry" 2011-09-19T02:00:10.473Z With regard to object-glasses, those of shortest focal length have the highest powers, and the longest eye-pieces have the lowest powers. Marvels of Pond-life A Year's Microscopic Recreations 2011-08-01T02:00:12.067Z One has an object-glass of four inches aperture and eight feet six inches focal length, with a field of about 1° 2′, which is very nearly the photographic field of the main telescope. Photographs of Nebul? and Clusters Made with the Crossley Reflector 2011-06-21T02:00:27.500Z The Ramsden or positive eye-piece consists of two lenses of equal focal length placed at a distance apart equal to two-thirds of the focal length of either lens. The New Gresham Encyclopedia Volume 4, Part 3: Estremoz to Felspar 2011-04-14T02:00:59.373Z For example, a powerful converging lens will focus parallel light rays closer to itself and will have a smaller focal length than a weak lens. College Physics for AP Courses 2015-08-12T00:00:00Z Thus, a lens with focal length 1 metre has a power of 1 diopter. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z Such microscopes may be good enough for the generality of purposes, but they do not, with glasses of given focal length, afford the same magnifying power as is done by instruments of better construction. Marvels of Pond-life A Year's Microscopic Recreations 2011-08-01T02:00:12.067Z The large mirror, the most important part of the telescope, has an aperture of three feet, and a focal length of 17 feet 6.1 inches. Photographs of Nebul? and Clusters Made with the Crossley Reflector 2011-06-21T02:00:27.500Z The distance of F from A B is called the focal length of the lens, and F itself is called the focus. A Text-Book of Astronomy 2011-01-05T03:00:57.347Z The power P of a lens is defined to be the inverse of its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z If the focal length is 2 metres, the power is � diopter. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z It had a six-inch speculum with a five foot focal length. The Life of Roger Langdon Told by himself. With additions by his daughter Ellen. [With a preface by H. Clifton Lambert.] 2010-12-21T22:55:56.210Z On account of the short focal length of the three-foot mirror, the photographic resolving power of the telescope is much below its optical resolving power. Photographs of Nebul? and Clusters Made with the Crossley Reflector 2011-06-21T02:00:27.500Z To the free end of D is fastened the mirror T, made from thin diaphragm glass about 11/2 centimetres diameter, and having a focal length of 40 inches. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 Note that the focal length and power of a diverging lens are defined to be negative. College Physics for AP Courses 2015-08-12T00:00:00Z It is obtained by taking the reciprocal of the focal length of the lens or mirror in metres. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z My two eyes haven't quite the same focal length and this often puts me out of the straight with a column of figures. The Salvaging Of Civilisation Lens, specially selected as to quality and focal length. Kodaks and Kodak Supplies 1914 The electric lamp L is about 8 c.p., and is placed just within the focus of a lens which has a focal length of 3/4 inch. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 The focal length f of a diverging lens is negative. College Physics for AP Courses 2015-08-12T00:00:00Z The power may also be obtained by dividing 39.37 by the focal length in inches. The New Gresham Encyclopedia Volume 4, Part 1: Deposition to Eberswalde 2011-04-14T02:00:57.977Z As the minimum focal length increases with the square of the aperture, a quite impracticable distance would be required to rival the resolving power of a modern telescope. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" An R. R. lens cannot be used at an opening greater than ⅛ its focal length, commonly designated as f. Kodaks and Kodak Supplies 1914 With regard to the lens required, the practice adhered to by most photographers is to use a lens having a focal length equal to the diagonal of the plate used. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 They tell you that the microscope has an objective with a 0.500 cm focal length and an eyepiece with a 5.00 cm focal length. College Physics for AP Courses 2015-08-12T00:00:00Z Photographic Query.—Given the diameter and focal length of a simple achromatic lens; at what distance from it must a diaphragm of given diameter be placed to give the best possible image? Notes and Queries, Number 235, April 29, 1854 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc. If we suppose the focal length to be 66 ft., a single lens is practically perfect up to an aperture of 1.7 in. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" Lens, specially selected as to quality and focal length. Kodaks and Kodak Supplies 1914 A lens having a focal length of 1/4 inch would magnify 24 times, and one with a focal length of 1/100th of an inch 600 times, and so on. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 What is the angular magnification of a telescope that has a 100 cm focal length objective and a 2.50 cm focal length eyepiece? College Physics for AP Courses 2015-08-12T00:00:00Z The first was made with a Newtonian telescope something less than seven feet focal length, a power of 222, and an aperture of four and a half inches. Sir William Herschel: His Life and Works The linear accuracy required is thus a function of the ratio of aperture to focal length. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" Move the two carefully until they are at a distance apart equal to the sum of the focal lengths of the lenses, and you will see a magnified image of the distant object. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers This magnifying power of a lens is always equal to the focal length divided by the distance at which we see small objects most distinctly, viz. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 If the binoculars have objective lenses with a 75.0 cm focal length, what is the focal length of the eyepiece lenses? College Physics for AP Courses 2015-08-12T00:00:00Z B is a double convex lens, which has a focal length of twenty inches. How it Works Dealing in simple language with steam, electricity, light, heat, sound, hydraulics, optics, etc., and with their applications to apparatus in common use Calculation shows that, if the aperture be 1⁄5 in., an achromatic lens has no sensible advantage if the focal length be greater than about 11 in. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" When these two lenses are made of focal lengths which are directly proportional to their dispersions, they give a practically colorless image at their common focus. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers In a double and equally convex lens of glass the focal length is equal to the radius of the spherical surfaces of the lens. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 Two concave lenses, of focal lengths 500 mm and 20 mm, are used in the construction of a telescope. College Physics for AP Courses 2015-08-12T00:00:00Z To avoid confusion, this focal length is known as the principal focus, and is denoted by the symbol f. How it Works Dealing in simple language with steam, electricity, light, heat, sound, hydraulics, optics, etc., and with their applications to apparatus in common use When parallel rays fall directly upon a spherical mirror the longitudinal aberration is only about one-eighth as great as for the most favourably shaped single lens of equal focal length and aperture. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" With such a lens the magnifying power of the telescope is measured by the ratio of the focal length of the objective to that of the eye lens. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers If the lens is a plano-convex the focal length is twice the radius of its spherical surfaces. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 Figure 25.34 A light bulb placed 0.750 m from a lens having a 0.500 m focal length produces a real image on a poster board as discussed in the example above. College Physics for AP Courses 2015-08-12T00:00:00Z First, we note that the line A B, or A B1, denotes the principal focal length of the lens, and A C, or A C1, denotes twice the focal length. How it Works Dealing in simple language with steam, electricity, light, heat, sound, hydraulics, optics, etc., and with their applications to apparatus in common use These he fixed in a piece of organ pipe, which served the purpose of a tube, the glasses being distant from each other by the difference of their focal lengths. The Astronomy of Milton's 'Paradise Lost' The Huygens eyepiece consists of two plano-convex lenses whose focal lengths are in the ratio of three to one. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers Add 1 to the number of times it is required to enlarge and multiply the result by the focal length of the lens in inches. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 The distance at which the image blurs, and beyond which it inverts, is the focal length of the lens. College Physics for AP Courses 2015-08-12T00:00:00Z The focal length of a lens is judged by the distance between lens and image when the object is far away. How it Works Dealing in simple language with steam, electricity, light, heat, sound, hydraulics, optics, etc., and with their applications to apparatus in common use Those taken on the American plan of using telescopes of so great focal length as to afford, without further enlargement, an image of the requisite size, gave notably better results. A Popular History of Astronomy During the Nineteenth Century Fourth Edition Both lenses have their convex surfaces toward the object glass, and their distance apart is equal to half the sum of their focal lengths. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers The magnifying power of such a lens may be found by dividing 6 inches by the focal length of the lens, 6 inches being the distance at which we see small objects most distinctly. Wireless Transmission of Photographs Second Edition, Revised and Enlarged 1919 To use a convex lens as a magnifier, the object must be closer to the converging lens than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z The diameter, focal length, and maker of the lens, would, if carefully and honestly stated by some twenty or thirty photographers, be extremely valuable. Notes and Queries, Number 236, May 6, 1854 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc Mirrors of seven, ten, even twenty feet focal length, were successively completed, and unprecedented magnifying powers employed. A Popular History of Astronomy During the Nineteenth Century Fourth Edition In order to ascertain the magnifying power which an eyepiece gives when applied to a telescope it is necessary to know the equivalent, or combined, focal length of the two lenses. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers The lens was of fifteen-inch focal length on a 6½×8½ plate. Pictorial Photography in America 1921 Figure 25.36 uses ray tracing to show how an image is formed when an object is held closer to a converging lens than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z Even when attached to a telescope giving an equivalent focal length of nearly 150 feet, the camera only gives a very tiny image of the planet. To Mars via The Moon An Astronomical Story It has a focal length of nearly 200 feet, and can be used either for photographic or for visual purposes. A Popular History of Astronomy During the Nineteenth Century Fourth Edition The equivalent focal length of a positive or Ramsden eyepiece is equal to three fourths of the focal length of either of the lenses. Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers The verniers are fitted with adjustable magnifying glasses, the telescopes have an aperture of 25 mm., focal length of 200 mm. Astronomical Instruments and Accessories The focal length f of a concave mirror is positive, since it is a converging mirror. College Physics for AP Courses 2015-08-12T00:00:00Z Professor Lowell's telescope is over 32 feet in focal length, and has an object glass of excellent quality 24 inches in diameter, the work of the celebrated Alvan Clark. To Mars via The Moon An Astronomical Story His efforts culminated, after mirrors of ten, twenty, and thirty feet focal length had successively left his hands, in the gigantic forty-foot, completed August 28, 1789. A Popular History of Astronomy During the Nineteenth Century Fourth Edition The diameter of this object-glass is thirty-six inches, and its focal length is fifty-six feet two inches. The Story of the Heavens We should have focal length of lens, size of box, and the length of the sliding, parts of it. Notes and Queries, Number 204, September 24, 1853 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc. The distance of the focal point from the center of the mirror is its focal length f . College Physics for AP Courses 2015-08-12T00:00:00Z Next Mr. Shadbolt says, and rightly, that when the pictures are seen from a less distance than the focal length of the lens, they appear to be increased in bulk. Notes and Queries, Number 203, September 17, 1853 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc. The tube was thereby enabled to be shortened by twice the focal length of the mirror in question. A Popular History of Astronomy During the Nineteenth Century Fourth Edition The exposure depends on a number of factors, among which are light, negative, focal length of lens, size of enlargement, stops, sensitiveness of paper, developer, temperature of developer, and length of development. Bromide Printing and Enlarging A Practical Guide to the Making of Bromide Prints by Contact and Bromide Enlarging by Daylight and Artificial Light, With the Toning of Bromide Prints and Enlargements This would also be about the focal length of the finished lens. On Laboratory Arts Just as for lenses, the shorter the focal length, the more powerful the mirror; thus, P = 1 / f for a mirror, too. College Physics for AP Courses 2015-08-12T00:00:00Z The remedy is nevertheless obvious, and consists in placing the stereographs at the same distance from the eyes as the focal length of the lens. Notes and Queries, Number 203, September 17, 1853 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc. A meniscus lens of the diameter of four inches should have a focal length of twenty inches, and will produce perfect landscape pictures fourteen inches square. Notes and Queries, Number 180, April 9, 1853 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc The increased focal length, permitting such objects as the moon to be photographed on a larger scale, should also reveal smaller details of structure and render possible higher accuracy of measurement. The New Heavens If this angle is increased for a mirror of a given diameter by decreasing its focal length, the divergence of the beam is increased and the beam-intensity is diminished. Artificial Light Its Influence upon Civilization The smaller the radius of curvature, the smaller the focal length and, thus, the more powerful the mirror. College Physics for AP Courses 2015-08-12T00:00:00Z Therefore the eye-glass should never be of greater focal length than that which makes the emergent pencils about equal in diameter to the pupil of the eye. Half-hours with the Telescope Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction. The distance of the principal focus from the lens is called the focal length of the lens, and from the diagrams we see that the more convex the lens, the shorter the focal length. General Science Photographed with a small camera lens of 1 inch aperture and 5 inches focal length. The New Heavens Some successful results were obtained with a 6-volt electric lamp possessing a coiled filament at the focus of a lens three inches in diameter and twelve inches in focal length. Artificial Light Its Influence upon Civilization An object is farther from the converging mirror than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z On the other hand, the eye-glass must not be of such small focal length that the image appears indistinct and contorted, or dull for want of light. Half-hours with the Telescope Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction. To overcome this obstacle to clear vision, and also to secure magnification, the focal lengths of the instruments were greatly extended. Scientific American Supplement, No. 832, December 12, 1891 The sharpness of the images given by the new telescope may be illustrated by some recent photographs of the moon, obtained with an equivalent focal length of 134 feet. The New Heavens This copy was made with a Harrison's globe lens of sixteen inches' focal length, and was a very sharp and accurate duplicate of the original. The Atlantic Monthly, Volume 12, No. 69, July, 1863 The distance from the center of the lens to its focal point is called the focal length f . College Physics for AP Courses 2015-08-12T00:00:00Z If no new adjustment is required for distinct vision, the spherical aberration is corrected, since the mean focal length and the focal length of the central rays are equal. Half-hours with the Telescope Being a Popular Guide to the Use of the Telescope as a Means of Amusement and Instruction. In the actual apparatus the sphere is an ordinary round-bottomed flask about 95 mm. in diameter, and the lens a simple double convex lens of about 90 mm. focal length. Scientific American Supplement, No. 483, April 4, 1885 The speed of a photographic lens depends on the ratio of the effective aperture to the focal length. How to Observe in Archaeology A reflecting telescope, of two feet focal length, by ditto. A General History and Collection of Voyages and Travels — Volume 14 The process of adjusting the eye’s focal length is called accommodation. College Physics for AP Courses 2015-08-12T00:00:00Z The measurements given in these instructions are for a lens of about 5 in. focal length. The Boy Mechanic: Volume 1 700 Things for Boys to Do The rapidity of a lens depends mainly on its aperture and its focal length. Scientific American Supplement, No. 492, June 6, 1885 A focal length of about six inches will be best for a quarter–plate camera. How to Observe in Archaeology Accordingly the mirror was made 1¼ inches in diameter, and a new lens, 8 inches in diameter, with a focal length of 150 feet was procured. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis This places the first image closer to the eyepiece than its focal length, so that the eyepiece will form a case 2 image as shown in the figure. College Physics for AP Courses 2015-08-12T00:00:00Z If the glass is not ground enough to bring the rays to a point within 5 ft., the coarse grinding must be continued, unless a longer focal length is wanted. The Boy Mechanic: Volume 1 700 Things for Boys to Do Note down this focal length, and proceed to measure your diaphragms in sixteenths of an inch. Scientific American Supplement, No. 492, June 6, 1885 The Emperor of Russia has presented to the Observatory of Dorpat, a magnificent telescope by Franenhofer, with a focal length of 13 feet, and an aperture of 9 inches; the cost was £1,300. The Mirror of Literature, Amusement, and Instruction Volume 12, No. 328, August 23, 1828 The focal length of the lens was 150 feet, and the mirror was placed about 15 feet within the principal focus. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis The focal length of an objective lens is different than the working distance. College Physics for AP Courses 2015-08-12T00:00:00Z The mirror of the telescope is 8 inches in diameter; its focal length, 5 feet; and the tube in which it is mounted, about 6 feet long. Men of Invention and Industry For example, a Ross half plate rapid symmetrical has a focal length of 7� in.; for convenience reduce this to sixteenths=120. Scientific American Supplement, No. 492, June 6, 1885 The 'microscope' consisted of a cardboard tube with a 13 cm focal length lens at one end and a Philips OAP12 photo-diode at the other with another lens in front of it. The Dawn of Amateur Radio in the U.K. and Greece: a personal view It was 8 inches in diameter; focal length, 150 feet; not achromatic. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis It is true that for any distant object and any lens or mirror, the image is at the focal length. College Physics for AP Courses 2015-08-12T00:00:00Z The object glass is three inches; the focal length forty-three inches; and the telescope, when drawn out, with the pancratic eyepiece attached, is about four feet. Men of Invention and Industry The Photographic Society of Great Britain have recommended that the diaphragms of all lenses should bear such relation to the focal length that each should require exactly double the exposure of the next smaller. Scientific American Supplement, No. 492, June 6, 1885 In 1844 he conceived the bold idea of constructing a reflector of two feet aperture, and twenty feet focal length, to be mounted equatorially. James Nasmyth: Engineer; an autobiography As the diameter of the lens was so small in comparison with its focal length, its want of achromatism was inappreciable. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis The distance between the eyepiece and the objective lens is made slightly less than the sum of their focal lengths so that the first image is closer to the eyepiece than its focal length. College Physics for AP Courses 2015-08-12T00:00:00Z If a constant of reproduction, for instance the focal length, be made equal for two colours, then it is not the same for other colours, if two different glasses are employed. The Project Gutenberg Encyclopedia Volume 1 of 28 The inner lens is an achromatic 3 1/4 inches diameter, its focal length being 30 inches. History and Practice of the Art of Photography The lines A B C represent parallel rays which pass through the lens, D D, and meet at F; this point being the principal focus, its distance from the lens is called the focal length. American Hand Book of the Daguerreotype The second condition conflicts with the first, for the radius is the difference between the focal length for parallel rays, and that for rays at the distance of the fixed mirror. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis To obtain the greatest angular magnification, it is best to have a long focal length objective and a short focal length eyepiece. College Physics for AP Courses 2015-08-12T00:00:00Z For example, it is possible, with one thick lens in air, to achromatize the position of a focal plane of the magnitude of the focal length. The Project Gutenberg Encyclopedia Volume 1 of 28 The diameter and focal length of a lens must depend in a great measure on the distance of the object, and also on the superficies of the plate or paper to be covered. History and Practice of the Art of Photography Dr. Herschel made many observations on this portion of the heavens, using a Newtonian reflector of twenty feet focal length, and an aperture of eighteen inches. The Mirror of Literature, Amusement, and Instruction Volume 10, No. 267, August 4, 1827 There are two ways of solving the difficulty: first, by using a lens of great focal length; and secondly, by placing the revolving mirror within the principal focus of the lens. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis Large and relatively flat mirrors have very long focal lengths, so that great angular magnification is possible. College Physics for AP Courses 2015-08-12T00:00:00Z In a very thin lens, in air, only one constant of reproduction is to be observed, since the focal length and the distance of the focal point are equal. The Project Gutenberg Encyclopedia Volume 1 of 28 The outer lens is a meniscus--that is bounded by a concave and convex spherical surface which meet--having a focal length of 18 inches. History and Practice of the Art of Photography This instrument consisted of a reflector on the "Front-view" construction, with a speculum 4 feet in diameter and of 40 feet focal length. Scientific American Supplement, No. 303, October 22, 1881 The eye-piece consists of a single achromatic lens, whose focal length is about two inches. Experimental Determination of the Velocity of Light Made at the U.S. Naval Academy, Annapolis Among the things to be considered are the focal lengths of the lenses and their relative placements as well as the size and location of the object. College Physics for AP Courses 2015-08-12T00:00:00Z These chromatic errors of systems, which are achromatic for two colours, are called the ``secondary spectrum,'' and depend upon the aperture and focal length in the same manner as the primary chromatid errors do. The Project Gutenberg Encyclopedia Volume 1 of 28 He then possessed a fine equatorial telescope of 18 inches aperture and 26 feet focal length, besides two smaller ones, all of the best quality. Is Mars habitable? A critical examination of Professor Percival Lowell's book "Mars and its canals," with an alternative explanation It was provided with a well-corrected object-glass having a focal length of 200 mm. and as used by me gave a magnifying power of 16 diameters. Scientific American Supplement, No. 303, October 22, 1881 They are building immense additional rooms, and are having a great telescope, twenty-seven feet in focal length, constructed. Maria Mitchell: Life, Letters, and Journals The distance from the center of the lens to the focal point is again called the focal length f of the lens. College Physics for AP Courses 2015-08-12T00:00:00Z My instrument was an excellent refractor of 3 3/4 inches aperture, and five feet focal length, with a power of one hundred. Story of Creation as Told By Theology and By Science The focal length was 24 feet 3 inches, and the eye-glass was 3 and a half feet above the ground floor. Great Astronomers It was of twelve feet focal length, and enabled Huygens to discover a new satellite of Saturn, and to determine also the true explanation of Saturn's ring. A History of Science — Volume 2 What is the focal length of 1.75 D reading glasses found on the rack in a pharmacy? College Physics for AP Courses 2015-08-12T00:00:00Z For example, if the distance to F in Figure 25.28 is 5.00 cm, then the focal length is f = –5.00 cm and the power of the lens is P = –20 D . College Physics for AP Courses 2015-08-12T00:00:00Z How far from the lens must the film in a camera be, if the lens has a 35.0 mm focal length and is being used to photograph a flower 75.0 cm away? College Physics for AP Courses 2015-08-12T00:00:00Z The contents of the northern hemisphere, so far at least as they could be disclosed by his telescope of twenty feet focal length, had been revealed. Great Astronomers He did not confine his efforts to simply lengthening the focal length of his telescopes, however, but also added to their efficiency by inventing an almost perfect achromatic eye-piece. A History of Science — Volume 2 Combine thin lens equations to show that the magnification for a thin lens is determined by its focal length and the object distance and is given by m = f / ⎛ f − do⎞ . College Physics for AP Courses 2015-08-12T00:00:00Z Your camera’s zoom lens has an adjustable focal length ranging from 80.0 to 200 mm. College Physics for AP Courses 2015-08-12T00:00:00Z What is the focal length of a makeup mirror that produces a magnification of 1.50 when a person’s face is 12.0 cm away? College Physics for AP Courses 2015-08-12T00:00:00Z What is the focal length of the lens used for the magnifying glass? College Physics for AP Courses 2015-08-12T00:00:00Z What is the focal length of the mirror? College Physics for AP Courses 2015-08-12T00:00:00Z |
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