10大关键单反技巧

无论你是刚刚学习摄影的新手,还是处于瓶颈期的老手,重新开始学习基础知识,都能给你带来新的突破。现在就让Chris Rutter给大家提供十条能够提高自己拍摄水平的必备技巧。或许数十年的磨练,才能带来一幅精彩的作品;但无论水平高低,掌握一些基础的摄影技巧或许就能拍摄出让人刮目相看的照片。接下来,我们就打算向大家介绍十条每个摄影师都应该掌握的基础拍摄技巧,从对焦到构图、从白平衡到光线条件,一针见血地指出初学者的常见问题,提高对于基本技巧的掌握,帮助大家使用最简单的方     

伊莫·麦凯伯

<正>Sylyester Mittee"我使用一支180mm镜头将画面聚焦在紧紧缠绕的绷带上。我看到过有些广告画面明显在模仿这幅作品,但他们永远无法捕捉这样一幅完美作品的精髓。轻微晃动给画面带来了独特的氛围。"     

The location of pyridine in sodium–silver–Y zeolite by powder synchrotron X-ray diffraction

The powder synchrotron X-ray diffraction pattern of a mixed sodium–silver–Y zeolite, Ag_56−xNa_xSi₁₃₆Al₅₆O₃₈₄ x≈19, saturated with pyridine, has been analysed by the Rietveld method to reveal positions for the adsorbed molecules. Cations are distributed over three sites, SII, constrained to 100% occupancy, with 17.2(1) and 14.8(1) Ag(1) and Na(1) ions per unit cell, respectively, SI′ with 18.3(1) Ag(2) ions per cell, and SI with 1.8(1) Ag(3) ions per cell. The refinement suggests that approximately 7.5 pyridine molecules are adsorbed per supercage, located in two sites within the cavities of the zeolite. Pyridine(1) is in the 12-ring window connecting supercages. Three molecules project through each window and approach the SII cations in a supercage, with an average Ag(1)–N distance of 3.17(2) Å. An SII cation can be linked to three pyridine(1) molecules from three separate windows. These sites are full with 5.98(2) molecules per supercage. Pyridine(2) is found in the supercage, oriented with its π electron density towards the SII cations, with its centre at 2.87(2) Å from Ag(1). The average occupancy was fixed at 1.5 molecules per supercage, corresponding to 20% of the pyridine content. A local ordering scheme can be postulated, whereby alternate supercages are filled by pyridine(1) and pyridine(2) molecules, efficiently filling the channels of the zeolite.     

Thermal degradation of high‐temperature fluorinated polyimide and its carbon fiber composite

High‐temperature polymers are being used for a broad range of applications, such as composite matrices for structural applications (e.g., high speed aircraft). Polyimides are a special class of polymers that meet the thermal and oxidative stability requirements for high temperature composite aerospace applications. A weight loss study was performed on a fluorinated polyimide resin and its carbon fiber composite in an effort to determine its thermal stability and degradation mechanisms. Experiments were conducted using a preheated oven and thermogravimetric analysis to obtain the weight loss. Regardless of the method used, the resin and composite exhibited excellent thermal stability (less than 1% weight loss) below 430°C, regardless of 2–20 min of exposure. After 20 min of exposure at 510°C, the composite remained relatively stable with only 5.3% weight loss using the oven technique, whereas the neat polyimide sustained 12.6%. When degradation occurred, it was found to be the result of thermolysis and oxidation (to a lesser extent). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

如何让你的照片充满活力

<正>本期重点:1使用仿制图章工具2转换黑白影调和调整反差3调整画面影调与色彩4调整高光与增加细节5使用蒙版工具强化色彩和反差6调整构图与使用可选颜色7使用自由变换与调节曲线一张优秀的照片如何脱颖而出?是什么让它显得与众不同?如果你需要建议让自己的照片变得出色,我们的专家很乐意在此提供     

拉直倾斜的建筑

<正>George Cairns告诉我们如何使用镜头校正命令完善建筑摄影作品我们敢打赌大部分建筑都有拔地而起的90度垂直外墙。但是在拍摄建筑物照片的时候,由于透视畸变,所有垂直线条向一点汇聚,外墙的下半部分往往要比上半部分看上去宽很多。     

The alpha attenuation test: assessing excessive daytime sleepiness in narcolepsy-cataplexy

Daytime sleep tendency was assessed in 10 drug-free patients with narcolepsy-cataplexy and 10 normals matched for age and gender. Following nocturnal polysomnography, the alpha attenuation test (AAT) and the multiple sleep latency test (MSLT) were administered during five sessions occurring at 2-hour intervals beginning at 0900 and 1000 hours, respectively. For the AAT, participants were polysomnographically recorded for 8 minutes while seated in an illuminated room with their eyes alternately opened and closed. Power spectral analyses of electroencephalograph (EEG) activity at 02-A1 (10 second epochs) were calculated using fast Fourier transformations (FFT) within the alpha frequency range (8-12 Hz) to obtain ratios of mean eyes-closed to mean eyes-open alpha power (i.e. the alpha attenuation coefficient, AAC). The narcoleptics were sleepier than the normals as indicated by a significantly smaller mean AAC and a significantly shorter mean latency to stage 1 on the MSLT. These findings suggest that the AAT may provide a quick and practical objective assessment of the excessive daytime sleepiness (EDS) associated with narcolepsy.