I had no luck with page floats in columnsets; according to the manual
they should work.
Hraban
\setuppapersize[A5,landscape]
\useMPlibrary[dum]
\definecolumnset[Two][n=2]
\starttext
\startcolumnset[Two]
\dorecurse{5}{1\recurselevel\samplefile{lorem}\par}
\startplacefigure[location=page,title={my caption}]%
\externalfigure[dummy][width=2\textwidth,height=.95\textheight]%
\stopplacefigure
\dorecurse{5}{2\recurselevel\samplefile{lorem}\par}
\stopcolumnset
\stoptext
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the
Wiki!
maillist : ntg-context@ntg.nl / https://www.ntg.nl/mailman/listinfo/ntg-context
webpage : https://www.pragma-ade.nl / http://context.aanhet.net
archive : https://bitbucket.org/phg/context-mirror/commits/
wiki : https://contextgarden.net
___________________________________________________________________________________
