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Chapters: Reciprocity. Source: Wikipedia. Pages: 45. Not illustrated. Free updates online. Purchase includes a free trial membership in the publisher's book club where you can select from more than a million books without charge. Excerpt: In photography and holography, reciprocity refers to the inverse relationship between the intensity and duration of light that determines the reaction of light-sensitive material. Within a normal exposure range for film stock, for example, the reciprocity law states that the film response will be determined by the total exposure, defined as intensity × time. Therefore, the same response (for example, the optical density of the developed film) can result from reducing duration and increasing light intensity, and vice versa. The reciprocal relationship is assumed in most sensitometry, for example when measuring a Hurter and Driffield curve (optical density versus logarithm of total exposure) for a photographic emulsion. Total exposure of the film or sensor, the product of focal-plane illuminance times exposure time, is measured in lux seconds. The idea of reciprocity, once known as BunsenRoscoe reciprocity, originated from the work of Robert Bunsen and Henry Roscoe in 1862. Deviations from the reciprocity law were reported by Captain William de Wiveleslie Abney in 1893, and extensively studied by Karl Schwarzschild in 1899. Schwarzschild's model was found wanting by Abney and by Englisch, and better models have been proposed in subsequent decades of the early twentieth century. In 1913, Kron formulated an equation to describe the effect in terms of curves of constant density, which J. Halm adopted and modified, leading to the "KronHalm catenary equation" or "KronHalmWebb formula" to describe departures from reciprocity. In photography, reciprocity refers to the relationship whereby the total light energy proportional to the total exposure, the product of the light intensity and exposure time...More: http://booksllc.net/?id=1046247 ... Read more

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Practical Guide to Astrophotography is a complete guide to amateur astrophotography, from planning and purchasing equipment through to making high-quality images. This book contains information that would otherwise take a long time and a lot of patience to learn.

It covers the commercial "hot products", comparing their features and ensuring that the reader chooses the best equipment – within his budget – for his chosen area. It covers the most common telescopes, software and cameras used for astrophotography by amateur astronomers, and describes step-by-step how to get from "dreaming about it" through buying the materials and building the system, to obtaining the best possible images. The combination of the product mix and practical processes covers a very large amateur astronomer user-base.

This is not only a guide to setting up, it’s also a book that readers will frequently take with them in the field to help them on their journey to make images of the stars. It’s targeted at providing practical knowledge and leverages "lessons learned" in actual field operations involved in astrophotography. This comprehensive book fills in all the blanks that are not fully covered in magazines or (multiple) other books.

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This book gives an informative and practical survey of today's topics in astrophotography, both its new experimental developments and its results. Based on the contributions to the international IAU workshop "Astrophotography" held in Jena in 1987, the various chapters deal with photoemulsions used in astrophotography, hypersensitization, calibration problems, the processing and use of astronomical photographs, and results of astrophotographical observations. This book is not only an indispensable addition to the libraries of astronomical observatories and institutes, but also contains interesting information for the ambitious amateur astrophotographer. ... Read more