Figure caption wider than surrounding text block

Question

I have an article to be written with 1 inch margins, with figures of course in the figure environment. [...] I now narrowed down the problem to the use of \abstract{...}. I use

\documentclass[12pt]{article}   
\usepackage[a4paper, margin=1in]{geometry}
\usepackage{graphicx,authblk}    
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}   
\usepackage{csquotes}

\begin{document}    
\abstract{Lorem ipsum dolor sit amet, \ldots}

\section{Test}    
Test

\begin{figure}
\centering
\includegraphics[width=0.8\textwidth]{fig_Test.pdf}
\caption{This is a long sentence used as caption. It has 
to be so long to illustrate my problem.}
\label{fig_Test}
\end{figure}

\end{document}

If I remove the \abstract directive, everything works fine. But as soon as the \abstract instruction is there, its formatting (narrower textblock than standard) is kept for the subsequent sections, and the captions are wider than the text block. What to do, if I do want to provide an abstract for the paper?

Answer 1

(edited this answer after the OP revealed some previously missing information)

If you want to write the Abstract using the directive

 \abstract{Lorem ipsum dolor sit amet...}

you must terminate the abstract section with a matching \endabstract directive:

 \abstract
 Lorem ipsum dolor sit amet...
 \endabstract

The \abstract directive does not actually take an argument. Thus, writing \abstract{Lorem ipsum ...} is equivalent to writing \abstract Lorem ipsum ....

However, it's much better (and certainly clearer, in my view) to write

\begin{abstract}
Lorem ipsum dolor sit amet...
\end{abstract}

Answer 2

• to have caption wide the text width special effort is needed :), so described problem is unlikely (i can't reproduce it)
• instead \graphics you should load \graphicx
• the way how the some packages is loaded is wrong, they had to outside of \ifpdf test
• minimal working example (mwe) is:

\documentclass[12pt]{article}
\usepackage{geometry}
\geometry{a4paper, margin=1in}

\usepackage[demo]{graphicx}
\usepackage{caption}

\usepackage{lipsum}

\begin{document}
\lipsum[11]
    \begin{figure}[ht]
\centering
\includegraphics[width=0.8\textwidth]{fig_Test.pdf}
\caption{This is a long sentence used as caption. It has to be so long to illustrate my problem.}
\label{fig_Test}
    \end{figure}
\end{document}