Optical font sizes: how do I set a fixed value?

Question

This is, for the moment, just an experiment with Minion Pro optical font sizes. I'm trying to produce a large letter g to compare the Caption, Normal, Subhead, and Display-size fonts. Here's the code:

% !TEX TS-program = XeLaTeX
\documentclass[a4paper,12pt,oneside]{article}
\usepackage{fontspec}
\begin{document}
\fontsize{72}{72}
\newfontfamily\fonta[SizeFeatures={{Size={5-120},Font=* Display}}]{Minion Pro}
\newfontfamily\fontb[SizeFeatures={{Size={5-120},Font=* Subhead}}]{Minion Pro}
\newfontfamily\fontc[SizeFeatures={{Size={5-120},Font=*}}]{Minion Pro}
\newfontfamily\fontd[SizeFeatures={{Size={5-120},Font=* Caption}}]{Minion Pro}

\fonta g \fontb g \fontc g \fontd g

\end{document}

but I get four identical letters g, and the only font in the .pdf is the Display-size font.

Am I doing something wrong (and, if so, what)? Or do these "intelligent fonts" think they're more intelligent than I am (a distinct possibility, BTW)?

---

Update:

I can reproduce @Herbert's answer. With LuaLaTeX, all four fonts are present. According to the log (trimmed), fontspec appears to be reporting the font definitions slightly differently. I have no idea how significant these differences are. For example:

XeLaTeX:

. * 'normal' with NFSS spec.:
. <5-120>"Minion Pro Subhead/ICU:script=latn;language=DFLT;"
. * 'small caps' with NFSS spec.:
. <5-120>"Minion Pro Subhead/ICU:script=latn;language=DFLT;+smcp;"
. * 'bold' with NFSS spec.:
. <5-120>"Minion Pro/B Subhead/ICU:script=latn;language=DFLT;"
. * 'bold small caps' with NFSS spec.:
. <5-120>"Minion Pro/B Subhead/ICU:script=latn;language=DFLT;+smcp;"
. * 'italic' with NFSS spec.:
. <5-120>"Minion Pro/I Subhead/ICU:script=latn;language=DFLT;"
. * 'italic small caps' with NFSS spec.:
. <5-120>"Minion Pro/I Subhead/ICU:script=latn;language=DFLT;+smcp;"
. * 'bold italic' with NFSS spec.:
. <5-120>"Minion Pro/BI Subhead/ICU:script=latn;language=DFLT;"
. * 'bold italic small caps' with NFSS spec.:
. <5-120>"Minion Pro/BI Subhead/ICU:script=latn;language=DFLT;+smcp;"

LuaLaTeX:

. * 'small caps' with NFSS spec.:
. <5-120>"name:MinionProSubhead:mode=node;script=latn;language=DFLT;+smcp;"
. * 'bold' with NFSS spec.:
. <5-120>"name:MinionPro/BSubhead:mode=node;script=latn;language=DFLT;"
. * 'bold small caps' with NFSS spec.:
. <5-120>"name:MinionPro/BSubhead:mode=node;script=latn;language=DFLT;+smcp;"
. * 'italic' with NFSS spec.:
. <5-120>"name:MinionPro/ISubhead:mode=node;script=latn;language=DFLT;"
. * 'italic small caps' with NFSS spec.:
. <5-120>"name:MinionPro/ISubhead:mode=node;script=latn;language=DFLT;+smcp;"
. * 'bold italic' with NFSS spec.:
. <5-120>"name:MinionPro/BISubhead:mode=node;script=latn;language=DFLT;"
. * 'bold italic small caps' with NFSS spec.:
. <5-120>"name:MinionPro/BISubhead:mode=node;script=latn;language=DFLT;+smcp;"

Answer 1

this works for me with LuaLaTeX and not with XeLaTeX. I suppose the optional arguments are only valid for LuaLaTeX:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Arno Pro}
\newfontfamily\fonta[SizeFeatures={{Size={12-80},Font=* Display}}]{Arno Pro}
\newfontfamily\fontb[SizeFeatures={{Size={12-80},Font=* Subhead}}]{Arno Pro}
\newfontfamily\fontc[SizeFeatures={{Size={6-11},Font=Minion Pro},{Size={12-80},Font=*}}]{Arno Pro}
\newfontfamily\fontd[SizeFeatures={{Size={12-80},Font=* Caption}}]{Arno Pro}

\begin{document}
Arno Pro \fontc Minion Pro\fontsize{14}{15}Arno Pro\par
\fontsize{50}{52}
\fontd Arno Pro Caption\par
\fontb Arno Pro Subhead\par
\fonta Arno Pro Display\par
\normalfont\normalsize normal font
\end{document}

my used fonts:

voss@shania:~/Test> pdffonts test.pdf
name                          type              encoding         emb sub uni object ID
----------------------------- ----------------- ---------------- --- --- --- ---------
LBZWCL+ArnoPro-SmText         CID Type 0C       Identity-H       yes yes yes      4  0
NMAHFW+MinionPro-Medium       CID Type 0C       Identity-H       yes yes yes      5  0
BHJMSX+ArnoPro-Caption        CID Type 0C       Identity-H       yes yes yes      6  0
FONMDX+ArnoPro-Subhead        CID Type 0C       Identity-H       yes yes yes      7  0
VYIITZ+ArnoPro-Display        CID Type 0C       Identity-H       yes yes yes      8  0