Kerning between V and / in Palatino and Euler

Question

Edit 1

I made the test with real palatino font and Neo-Euler, with the same result (As far as I can see)

\documentclass{standalone}
\usepackage{fontspec}
\setmainfont[] {PalatinoLTStd-Roman.otf}
%\setmathrm [] {}
\usepackage{unicode-math}
\setmathfont[math-style=upright]{euler.otf}
\usepackage{siunitx}

\begin{document}

\begin{tabular}{ll}
Text  & MV/m \\
equation & $MV/m$\\
two mathrm & $\mathrm{MV}/\mathrm{m}$\\
one mathrm & $\mathrm{MV/m}$\\
siunitx & \si[per-mode = symbol]{\mega\volt\per\metre}
\end{tabular}

\end{document}

Original

I am using palatino with euler as shown below.

I noticed a big space between V and /. I am not sure if it is because the slash is a binary operator or because the kerning is incorrect. I have this problem with the unit and it shown also with siunitx. Do you also think it is too much space?

\documentclass{standalone}

\renewcommand{\rmdefault}{ppl} % rm
\linespread{1.05}        % Palatino needs more leading
\usepackage[scaled]{helvet} % ss
\usepackage{courier} % tt
\usepackage{eulervm} % a better implementation of the euler package (not in gwTeX)
\normalfont
\usepackage[T1]{fontenc}
%\usepackage{verbatim}
\usepackage{siunitx}

\begin{document}

\begin{tabular}{ll}
Text  & MV/m \\
equation & $MV/m$\\
two mathrm & $\mathrm{MV}/\mathrm{m}$\\
one mathrm & $\mathrm{MV/m}$\\
siunitx & \si[per-mode = symbol]{\mega\volt\per\metre}
\end{tabular}

\end{document}

Answer 1

If you modify your MWE to use article (to avoid artefacts of standalone) and add \showoutput to your document you will see that

Text  & MV/m \\

produces

........\T1/ppl/m/n/10 M
........\T1/ppl/m/n/10 V
........\T1/ppl/m/n/10 /
........\T1/ppl/m/n/10 m

So there is no font-specified kern between V and / in that font.

equation & $MV/m$\\

produces

........\U/zeur/m/n/10 M
........\U/zeur/m/n/10 V
........\kern0.83
........\kern-0.56
........\U/zeur/m/n/10 =
........\U/zeur/m/n/10 m

Net result is a small positive kern here, but note the / is from a different font.

looking in uzeur.fd we see this font is zeurm10 and looking at the output of

tftopl zeurm10 

we see

(CHARACTER C V
   (CHARWD R 0.646)
   (CHARHT R 0.691)
   (CHARIC R 0.083)

So V has a italic correction of .83pt which accounts for the first kern added.

the same file also has

 (LABEL C V)
   (KRN O 177 R 0.056)
   (KRN O 75 R -0.056)

which says there is a kern of -.56pt between (C)haracter V and (Oc)ctal 75 which is hex 61 which is = the slot with / in this encoding.

two mathrm & $\mathrm{MV}/\mathrm{m}$\\

produces

........\hbox(6.97992+0.15997)x16.67993
.........\OT1/ppl/m/n/10 M
.........\OT1/ppl/m/n/10 V
........\U/zeur/m/n/10 =
........\OT1/ppl/m/n/10 m

No kern, / again coming from the math font.

and

one mathrm & $\mathrm{MV/m}$\\

produces

........\hbox(7.48999+2.5)x30.52988
.........\OT1/ppl/m/n/10 M
.........\OT1/ppl/m/n/10 V
.........\U/zeur/m/n/10 =
.........\OT1/ppl/m/n/10 m

No kern again.

siunitx & \si[per-mode = symbol]{\mega\volt\per\metre}

produces

........\hbox(7.23492+1.20496)x31.56982
.........\T1/ppl/m/n/10 M
.........\T1/ppl/m/n/10 V
.........\T1/ppl/m/n/10 /
.........\T1/ppl/m/n/10 m

the same setting as for text with / coming from the same font as the letters with no kerning.