I am automating the creation of books using ConTeXt with a graphic design graduate student at the Rhode Island School of Design.

The book cover is created using MetaPost inside a ConTeXt source file.

The graphic designer tells me it is very common to specify the interletter spacing, or tracking, and in fact, he considers this capability to be essential.

I understand that these, so called, microtypography capabilities are present in pdfTeX fully, but only partially present in LuaTeX (protrusion and expansion), although tracking can be set in a way using \kerncharacters[0.5] in LuaTeX.

However, the quality of the typesetting produced by LuaTeX is completely inadequate, while the quality of the typesetting produced by pdfTeX is very good.

Am I miss-understanding the differences in capability between pdfTeX and LuaTeX in this regard?

Relevant examples follow and PDFs are attached.


I processed the following ConTeXt source file using MKII:

This is pdfTeX, Version 3.1415926-1.40.10 (Web2C 2009) (format=cont-en 2011.8.13)
ConTeXt  ver: 2011.05.18 18:04 MKII  fmt: 2011.8.13  int: english/english

===== START MKII EXAMPLE =====
\pdfminorversion=5

\definepapersize[LG1][width=9.3in,height=6.87in]
\definepapersize[LP1][width=9.55in,height=7.12in]

\setuppapersize[LG1][LP1]

\setuplayout[location=middle,marking=off]

\setuppagenumber[state=stop]

\startMPenvironment
  \usetypescript[modern][ec]
  \switchtotypeface[modern][7.0pt]
  \setupinterlinespace
  \def\stretchedspacefactor{4}
  \def\stretchedspaceamount{0.25em}
\stopMPenvironment

\startuniqueMPgraphic{cover}
  cover_paper_width := 9.55in;
  cover_paper_height := 7.12in;
  left_margin := 0.347222222222in;
  top_margin := 0.347222222222in;
  bottom_margin := 0.347222222222in;

  draw (0, 0)--(cover_paper_width, cover_paper_height)
    withpen pencircle scaled 1bp withcolor white;

  picture labelText;
  labelText := btex {\vbox{\hsize 2.38888888889in \baselineskip 10.5pt
                           T\hskip 0.25em\stretchednormalcase{HIS BOOK
                             CONTAINS 988 TWEETS POSTED TO TWITTER BY
                             LADYGAGA FROM MARCH 27, 2008 TO AUGUST 5,
                             2011. IT WAS PUBLISHED ON DEMAND ON AUGUST
                             14, 2011}}} etex;
  labeloffset := 0bp;
  label.lrt(labelText, (left_margin,
                        cover_paper_height - top_margin));

\stopuniqueMPgraphic

\defineoverlay[cover][\uniqueMPgraphic{cover}]

\starttext

\title{}
\setupbackgrounds[paper][background={cover}]

\stoptext
===== STOP MKII EXAMPLE =====

I processed the following ConTeXt source file using MKIV:

this is luatex, version beta-0.70.1-2011051908 (rev 4277)
ConTeXt  ver: 2011.05.18 18:04 MKIV  fmt: 2011.7.13  int: english/english

===== START MKVI EXAMPLE =====
\pdfminorversion=5

\definepapersize[LG1][width=9.24in,height=6.87in]
\definepapersize[LP1][width=9.49in,height=7.12in]

\setuppapersize[LG1][LP1]

\setuplayout[location=middle,marking=off]

\setuppagenumber[state=stop]

\definefont[LabelFont][Serif sa 0.583]

\startuniqueMPgraphic{cover}
  cover_paper_width := 9.49in;
  cover_paper_height := 7.12in;
  left_margin := 0.347222222222in;
  top_margin := 0.347222222222in;
  bottom_margin := 0.347222222222in;
 
  draw (0, 0)--(cover_paper_width, cover_paper_height)
    withpen pencircle scaled 1bp withcolor white;

  picture labelText;
  labelText := btex {\vbox{\hsize 2.38888888889in \baselineskip 10.5pt \LabelFont
                           {\kerncharacters[0.5]
                            THIS BOOK CONTAINS 988 TWEETS POSTED TO
                            TWITTER BY LADYGAGA FROM MARCH 27, 2008
                            TO AUGUST 5, 2011. IT WAS PUBLISHED ON
                            DEMAND ON AUGUST 14, 2011}}} etex;
  labeloffset := 0bp;
  label.lrt(labelText, (left_margin,
                        cover_paper_height - top_margin));

\stopuniqueMPgraphic

\defineoverlay[cover][\uniqueMPgraphic{cover}]

\starttext

\title{}
\setupbackgrounds[paper][background={cover}]

\stoptext
===== STOP MKVI EXAMPLE =====

The MKII PDF