摄影曝光原理纪要(一)

若要实实在在的掌握摄影曝光技术,必须对一些光度学名词概念有些了解…弄懂感光材料(胶片、相纸与电子感光元件)的感光特性,才能弄懂曝光的基本原理;曝光准则A:"景物的实际曝光范围应落在胶片的有效感光范围之内",曝光准则B:"照片上主体影像的影调应与主体景物相符";各种测光装置(曝光表)及其用法;通过实际拍摄积累经验,才能熟练掌握曝光技术。     

摄影曝光原理纪要(三)

若要实实在在的掌握摄影曝光技术,必须对一些光度学名词概念有些了解,弄懂感光材料(胶片、相纸与电子感光元件)的感光特性,才能弄懂曝光的基本原理.曝光准则A:“景物的实际曝光范围应落在胶片的有效感光范围之内”.曝光准则B:“照片上主体影像的影调应与主体景物相符”.各种测光装置(曝光表)及其用法.通过实际拍摄积累经验,才能熟练掌握曝光技术.     

摄影曝光原理纪要(四)

若要实实在在的掌握摄影曝光技术,必须对一些光度学名词概念有些了解,弄懂感光材料(胶片、相纸与电子感光元件)的感光特性,才能弄懂曝光的基本原理。曝光准则A:"景物的实际曝光范围应落在胶片的有效感光范围之内"。曝光准则B:"照片上主体影像的影调应与主体景物相符"。各种测光装置(曝光表)及其用法。通过实际拍摄积累经验,才能熟练掌握曝光技术。     

摄影曝光原理纪要（五）

若要实实在在的掌握摄影曝光技术,必须对一些光度学名词概念有些了解,弄懂感光材料（胶片、相纸与电子感光元件）的感光特性,才能弄懂曝光的基本原理。曝光准则A：“景物的实际曝光范围应落在胶片的有效感光范围之内”。曝光准则B：“照片上主体影像的影调应与主体景物相符”。各种测光装置（曝光表）及其用法。通过实际拍摄积累经验,才能熟练掌握曝光技术。     

摄影曝光原理纪要（二）

若要实实在在的掌握摄影曝光技术,必须对一些光度学名词概念有些了解,弄懂感光材料（胶片、相纸与电子感光元件）的感光特性,才能弄懂曝光的基本原理;曝光准则A：“景物的实际曝光范围应落在胶片的有效感光范围之内”,曝光准则B：“照片上主体影像的影调应与主体景物相符”;各种测光装置（曝光表）及其用法;通过实际拍摄积累经验,才能熟练掌握曝光技术。     

副曝光超增感法和加热超增感法

拍摄非常暗的被摄体(低照度长时间曝光),或高速摄影(瞬时间曝光)时,要求照相胶片和平板的感光度要高。长时间曝光的摄影和短时间曝光的摄影所采用的有效方法不同。本文研究了在摄影前提高感光度的超增感法。低照度长时间曝光摄影的有效方法有:①预曝光法;②加热法;③冷却法(在低温下曝光);④蒸馏水法;⑤弱碱液法(氨水、硼砂、胺类,例如三乙醇胺等);⑥银盐法(氨化钨酸银溶液等和⑤合用)等。在摄影前用这些方法进行处理都是有效的。高照度瞬时间曝光摄影时,用摄影后显     

电影胶片的曝光与画面影调

胶片是电影影像的载体。电影摄影师通过对胶片的正确曝光,使被摄体的影像在胶片上得到最佳的记录。因此,科学地正确地了解和掌握胶片的感光特性,并创造性地将其运用到艺术创作当中去,是一个电影摄影师应具有的专业技能。然而,在实际的电影摄影工作中,有的摄影师并不...     

指尖上的多重曝光

正我们将通过3个简单的步骤,告诉你如何用iOS平台上的App"MultiExpo"实现如胶片相机一样的多重曝光效果。以前,多重曝光功能是多数胶片相机和少数数码相机才具备的功能。随着智能手机的兴起,这种极富创意的摄影形式又得到了一次易用性上的飞跃。如今,在iPhone上你只需要动动手指,就能完成一幅效果出众的多重曝光作品。当然,这离不开本文的主角:MultiExpo。这款App的界面十分简单。制作一张多重曝光作品,只需3个步骤,花费时间不超过5分钟。无论是与胶片时     

按快门说曝光

对于摄影人来说．每按动一次快门，对胶片就完成了次曝光，这就意味着一幅新的影像将要诞生。，你的曝光准确与否．将决定你的这个“新生儿”．是健康的，还是残疾的，健康的“新生儿”，将是反差适中层次丰富，色彩鲜艳，影纹清晰质感强、“残疾儿”那就会是：影调灰暗．     

质疑自动曝光补偿

现代 13 5单反相机大多配有自动曝光补偿的功能。当拍摄主体与大面积的浅背景或大面积的深背景亮度反差较大时 ,或者追求高调或低调摄影效果时 ,需要增加或减少 1～ 2档曝光 ,这时使用自动曝光补偿功能非常方便。即使没有自动曝光补偿功能的相机 ,也可以通过调节相机的胶片感光度设定的方法来实现曝光补偿。因为自动曝光补偿调节机构 ,实际上是与感光度调节机构连动的 ,只不过自动曝光补偿的操作更直观、更简便罢了。自动曝光补偿是怎样增加或减少曝光量的 ?对照片的画面质量产生什么影响 ?我们知道 ,控制光线通过镜头进入相机的装置只有光…     

一种基于数字图像合成的扩展动态范围方法

数码相机中CCD/CMOS图像传感器的饱和电流和背景噪音使得一次曝光很难超过60-80dB 的动态范围。根据人眼对灰度图像的识别特性,可以采用对相同景物二次不同曝光图像软件合成的算法来获取高动态范围的图像。实验结果显示,当景物画面各部分光照明显差别时,这种方法能有效地获得全部细节信息。     

钎焊环检测中的图像拼接方法研究

钎焊环检测系统中,采集的图像序列可能具有不完整环或重叠环。通过调整传送带速度和设置固定相机的曝光时间,确定了2幅图像的重叠区域;将图像去噪、灰度化和二值化,得到了具有清晰轮廓的图像;然后结合LSSVM和CA对图像边缘进行了检测,利用互信息法实现了图像配准;最后采用渐入渐出法进行了图像融合,得到了最终的拼接图像。实验表明,这种方法可以快速准确地实现钎焊环图像的拼接。     

复杂振动引起的图像退化分析与仿真

平台振动导致光学系统在曝光时间内与景物产生相对运动,严重影响了成像质量,而图像的退化模式可能并不单一,针对目前难于仿真高阶多模的复杂振动引起的图像退化问题,提出了基于像移矩阵的微分动态像移路径图像退化法,全面考虑了振动的空域和频域特性对图像退化的综合作用.从而在实际应用中只要已知振动函数,便可以通过一幅清晰的图像仿真得...     

Aberration measurement of photolithographic lenses by use of hybrid diffractive photomasks

In optical lithography the degradation of image quality due to aberrations present in the exposure tool is a serious problem. Therefore it is desirable to establish a reliable aberration measurement procedure based on the analysis of printed images in the photoresist. We present what is to our knowledge a new method for characterizing the aberrations of an exposure tool using a hybrid diffractive photomask. By utilizing each different impact on the aberrated image from each diffracted illumination, we were able to extract the aberration present in the stepper system. We experimentally verified this method with a G-line stepper and verified its spherical aberration astigmatism.     

Comparison of Flash Light Sources by the Open Shutter Method

Subject movement during a flash exposure gives image blur. In special cases, e.g. flash shadowgraphs of rifle bullets, densitometric study of this image blur can reveal information as to the light intensity-true characteristics of the flash light source used. Such an experiment and the method of analysis is outlined and the intensity-time (image density-time) curves of two flash light sources shown.     

LIP多重微区域分解算法扩展数字图像动态范围

CCD/CMOS 图像传感器的饱和电流和背景噪音使得一次曝光很难超过 60-80dB 的动态范围。用 LIP(Logarithmic image processing)模式将图像转换为灰色调函数,再将基于 LIP 模式的非线性多重微区域图像分解算法进行改进,可以适应不同亮度的单幅图像处理,提高了可分辨信息量和图像对比度,同时抑止了噪声。质量评价显示,该算法能将 MOS 等级四的源图像提高到等级一。     

计算机X线摄影头颅标准照片的测定

目的：计算机X线影像（CR）应用于头颅、制定标准以提供临床丰富诊断信息的照片。方法：选择三组不同曝光条件照射、制定标准测试点通过仪器对影像密度测试，并与普通屏－片进行对照、综合评价。结果：通过CR头颅正侧位片的测定，总结出头颅数字影像的标准。结论：计算机X线摄影在医学影像领域中越加占主导地位，以某一部位、位置的照片质量标准作为基点，以照片质量标准的检测条件作为原则，建立一整套完整的数字影像质控体系。     

医学数字摄影中，单纯追求影像质量不可取

在使用医用X-线胶片进行放射摄影时,胶片上的影像密度在冲洗后就不变了,X-线曝光量基本上是规范化的;但是,在数字摄影时,由于曝光产生的信息要经过后期处理,才能获得最终的影像,曝光和后期处理有很大的调整范围;影像的质量决定于信嘈比,而增加曝光量确实可以提高信嘈比,因此往往为了获得最佳的影像质量而追求最大的信嘈比,以便获得最佳影像质量,直接后果是病人得接受较高的射线剂量。但有时适当的影像质量就足可以满足诊断要求,就不应该让病人接受不必要的射线照射,因为过高的射线照射是极其有害的。     

High-speed flash exposure with compact digital cameras

Abstract

A technique was developed to allow the use of external flash at image sensor exposure times lower than the manufacturer’s specified maximum sync speed of a compact digital camera. By correlating light meter measurements with brightness readings of a grey card, a method to use the digital camera image sensor to measure light from flash units was developed. The flash discharge curve was derived and integrated to develop a mathematical model for clipped flash output. Utilising experimental data, the model was validated and parameterised for flash units. A computer program was created to calculate settings for correct flash exposure.     

Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs

PURPOSE: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. BACKGROUND: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. METHODS: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point; and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. RESULTS: The results of this study indicate that-contrary to what was supposed-the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. CONCLUSIONS: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended.