Problem with subfiles project

Question

Everyone!

I'm a bit new with latex and I'm trying to create a project with a few subfiles and I found a problem that I just dont understand. I will first put you in context. My directory distribution is as follows:

Apuntes/
|Apuntes_radio.tex  (This is the main file)
|paquetes.sty   (This is the preamble file)
|temas/
|->Introduccion/
|->|->Introduccion.tex (This is the subfile)
|->|->img_intro/  (And this is the folder where the images for this subfile will be)
|->|->|->espc_EM.png

My main file is

\documentclass[a4paper,11pt]{book}
\usepackage{import}
\usepackage{paquetes}
\usepackage{subfiles}

\usepackage{makeidx}
\makeindex

\title{Apuntes de Radiactividad y Aplicaciones (3º Física)}
\author{Samuel G. Guerrero}
\date{Febrero 2020}

\begin{document}

\frontmatter
\maketitle


\mainmatter
\chapter{Introducción}

\subfile{temas/Introduccion/Introduccion}

\end{document}

And the subfile is a bit long, so I'll show you where latex says the problems are:

\documentclass[../../Apuntes_radio.tex]{subfiles}

\graphicspath{
  {"temas/Introduccion/img_intro/"} %images path for the main file
  {"img_intro/"}                    %images path for THIS subfile
}

\begin{document}

.....[some junk]....

\begin{figure}[h!]
\centering
\includegraphics[scale=0.5]{espc_EM}
\caption{Espectro electromagnético.}
\label{fig:espc_EM}
\end{figure}

.....[some junk]....

\begin{wrapfigure}{l}{0.46\textwidth}
\includegraphics[scale=0.5]{espc_incandesc}
\label{fig:espc_incandesc}
\caption{Espectro de una lámpara incandescente}
\end{wrapfigure}

.....[some junk]....

\end{document}

And the preamble file is:

\ProvidesPackage{paquetes}

\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[spanish, es-tabla]{babel}
\usepackage{url}
\usepackage{amsmath}
\usepackage{wrapfig}
\usepackage{caption}
\usepackage{appendix}
\usepackage{multirow}
\usepackage{pdflscape}
\usepackage{listings}
\usepackage{titlesec}
\usepackage{csquotes}

\topmargin=-2cm
\oddsidemargin=-1cm
\evensidemargin=-1cm
\textwidth=17.5cm
\textheight=25cm
\footskip=20pt

\addto\captionsspanish{\renewcommand{\chaptername}{Tema}} %cambiar "capitulo" por " tema%


\titleformat{\chapter}[hang] 
{\normalfont\huge\bfseries}{\chaptertitlename\ \thechapter.}{10pt}{}

Now the problem

As it is, I have no trouble compiling the subfile individualy. It shows me no errors and looks as I want it. The problem comes when I try to compile the main file (Apuntes_radio.tex), it gives me this error:

the long one saying:

! Package pdftex.def Error: File `\es@period@code espc_EM.pdf' not found: usingdraft setting.See the pdftex.def package documentation for explanation.Type H for immediate help.... \includegraphics[scale=0.5]{espc_EM}

Can anyone tell what it is? I've sorted the 'Missing $ inserted' error before, but this time I'm pretty sure it's not a symbol missing, mainly because the subfile does compile by itself without problems! I've lost a day and a half already to this...

Thanks in advance!!

Answer 1

Remove the quotes from the graphicspath declaration. Quote are unneeded as there are not spaces (and with a current latex also in the other case) and with spanish they actually harm here as spanish makes the " active.

\graphicspath{
  {temas/Introduccion/img_intro/} %images path for the main file
  {img_intro/}                    %images path for THIS subfile
}