Resize image caption font in HTML RMarkdown output

Question

I would like to reduce the font size for all image captions in the R Markdown document. The end result is HTML, and I work in R Studio. To load an image, I use the include_graphicsfrom function knitrbecause I was told that this is the best way (see here ). My .Rmd file:

---
title: "ppp"
author: "ppp"
date: "July 4, 2017"
output: 
  html_document: 
    fig_caption: yes
---

```{r setup, include=FALSE}
library(knitr)
opts_chunk$set(echo = FALSE)
```


```{r foo, fig.cap="$f_{p}$ as a function of $g$ for various values of $r=\\frac{\\rho_{w}}{\\rho_{a}}$"}
# All defaults
include_graphics("download.jpg")
``` 

This is regular text.

Corresponding conclusion:

As you can see, the font size of the header and the font size of the plain text are exactly the same, which doesn’t look so good. How can I solve this problem?

Answer 1

CSS Rmd (- YAML):

<style>
p.caption {
  font-size: 0.6em;
}
</style>

:

(Chrome: → Inspect), , HTML caption:

<p class="caption"> ... </p>

CSS- ( ) 60% .

---