This question is brought about by my recent viewing of Xiao Hua/Little Flowers (1979) featuring a youthful 19 y.o. Joan Chen/Chen Chung. My copy of the video was full frame and, honestly, it looked okay to me. I could not detect anything that was obviously cropped so I could believe that full frame is the OAR but I could be wrong. I usually think of the mid-60's as the line of demarcation for HK films (in general) but I do not know what is the appropriate timeline for Mainland films. With the Cultural Revolution being from 1966-1976(?), I could imagine a technological lag into the late '70s. Going through my collection, the closest film from that era that I could find is the 1981 Legend of Tianyun Mountain and it is widescreen. But from wikipedia, the 1964 musical East is Red seems to be widescreen, so there's a bullet in my hypothesis.

It depends on what you mean by "widescreen" -- is the expression used in relation to video (DVD) formats, or in relation to widescreen projection processes such as standard spherical widescreen (1:1.85) or anamorphic Panavision/Cinemascope (1:2.35)?

If it's the latter, then I'm sure such photographic and projection processes have been in place in China for quite some time. The US isn't the only country in the world that can claim "widescreen" projection processes as a "pioneer" of such since their inception in the fifties...

In fact, a pretty basic Google of the words "China" and "widescreen" produced the following result:

http://www.china.org.cn/english/features/film/84966.htm

Which, if you read not so far through the paragraphs within, you'll discover that China produced its first "widescreen" motion picture (in this instance, referring to the "Cinemascope" format) all the way back in 1960. Thereby, excepting the Cultural Revolution, where there were no films produced between 1966 and 1972, China first dabbled in "widescreen" format films a measly forty seven years ago.

Ah, thanks for pointing out that my original inquiry was not very clear. So let me append to it in hopes of additional clarity. To wit, a) does anyone know what the OAR of Xiao Hua is, and b) when did widescreen/cinemascope film presentation become commonplace/standard, i.e., the norm, for mainland films? I'm basically looking for a simple rule of thumb that my little pea brain can latch on to and, hopefully, retain.

Tagentially, as is my wont, GZ Beauty has a relatively new (to me) DVD series of releases that feature some classic Chinese films, such as Rickshaw Boy, Third Sister Liu and Lin's Family Shop. Xiao Hua, which is also part of this series, and Trouble-Shooters, an obscure and admittedly lesser Ge You film that presages his latter role in Dream Factory by Feng Xiaogang both have excellent English subs, unlike some other subbed series I can think of. And I almost forgot, Zhang Yuan's Seventeen Years (1999) featuring the lovely Li Bingbing is also part of this catalog...time to replace my old vcd!