2.1 帧 Frame

帧：胶片概念当中，一帧即为一格胶片。

In filmmaking, video production, animation, and related fileds, a frame is one of the many still images which compose the complete moving picture.

帧率：一秒钟播放帧数的量。

Frame rate (expressed in frames per second or FPS) is the frequency (rate) at which consecutive images called frames appear on a display.

在计算动画的一个镜头或一个动作的时间(长度)时，除了以秒、分为单位还要精确到“帧”为单位。比如 1秒有24帧，24FPS, 相当于把一秒分成了24等分。

When calculating the time of an animated shot or action, we do not just indicate as ‘hour, minute, second’, as well as 'frame'. 

For example, 24 FPS means 24 frames per second.

TIPS：

The temporal sensitivity and resolution of human vision varies depending on the type and characteristics of visual stimulus, and it differs between individuals. The human visual system can process 10 to 12 images per second and perceive them individually, while higher rates are perceived as motion.

                           所以，从现在开始……

                             So, from now on...

                                      养成按“帧”计时的习惯!
                  Use ‘frame’ to calculate your animation time!

                                                                Stopwatch

电影 Film：24fps

        电视 Television（PAL）：25fps

        电视 Television（NTSC）：29.97fps

        电脑显示器 Computer monitor：60 fps

                                                  TIPS

NTSC——全称为National Television SystemCommittee，是1952年12月由美国国家电视系统委员会（NationalTelevision System Committee，缩写为NTSC）制定的彩色电视广播标准。采用正交平衡调制的技术方式，画面比例4:3。每秒30帧（30fps）。美国、加拿大、墨西哥等大部分美洲国家以及台湾、日本、韩国、菲律宾等均采用这种制式。

NTSC, named after the National Television System Committee, is the analog television color system that was introduced in North America in 1954 and stayed in use until digital conversion. The NTSC standard was used in most of NorthAmerica and western South America, Liberia; Myanmar, SouthKorea, Taiwan, Philippines, Japan, and some Pacific island nations and territories.

PAL——全称为逐行倒相（Phase Alternating Line），采用逐行倒相正交平跟调幅技术，克服NTSC的相位敏感造成的彩色失真问题。每秒25帧（25fps）。中国、德国、英国等世界上大部分地区都是采用PAL制式。Phase Alternating Line (PAL)is a color encoding system for analog television used in broadcast television systems in most countries broadcasting at 625-line / 50 field (25frame) per second (576i). PAL was adopted by all European countries, by all of Africa that had never been a French colony, by Argentina, Brazil, Paraguay, and Uruguay, by all of Asia, and by Oceania.