Well with
\definefontfamily[mainface][serif][Minion Pro][opticalsize=yes]
It does work. But I just wonder why some people could omit this option? Is
there a bug?

Will this be omitted in later distributions?

Results has been attached, 4 complete build result for you to analyze.

南京大学 现代工程与应用科学学院 2013级
罗晨星
Luo Chenxing
—————————————
chenxing.luo@gmail.com


2014-03-10 10:23 GMT+08:00 Wolfgang Schuster <schuster.wolfgang@gmail.com>:

>
> Am 10.03.2014 um 02:05 schrieb Wolfgang Schuster <
> schuster.wolfgang@gmail.com>:
>
> > Hi,
> >
> > can you run the attached file and show me the resulting pdf file?
>
> Can you also try what happens when you enable optical sizes!
>
> \definefontfamily[mainface][serif][Minion Pro][opticalsize=yes]
>
> \setupbodyfont[mainface]
>
> \starttext
> Hello World!
> \stoptext
>
> Wolfgang