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            17/03 — 2020
            <div class="stats">
              <span class="stats-number">
                32.36
              </span>
              <span class="stats-unit">cm</span>
              &nbsp
              <span class="stats-number">
                3.2
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          <span class="post-title">
            Font Size Fallacies
          </span>
          <div class="post-text">
            <p>I am not an expert with fonts, but I do have some
experience <sup id="fnref1"><a href="#fn1" rel="footnote">1</a></sup>, and common sense. This post aims to debunk some
misconceptions about font sizes!</p>

<p>11 px on your display is <em>probably not</em> 11 px on my display.
Let&#39;s do some quick math. I have two displays, 1366x768 @
21&#8221; and another with 1920x1080 @ 13&#8221;, call them <code>A</code> and
<code>B</code> for now.</p>

<p>Display <code>A</code> has 1,049,088 pixels. A pixel is a square, of
side say, <code>s</code> cm. The total area covered by my 21&#8221; display
is about 1,066 cm<sup>2</sup> (41x26). Thus,</p>

<pre><code>Display A
Dimensions: 1366x768 @ 21&#34; (41x26 sq. cm)
1,049,088 s^2 = 1066
            s = 0.0318 cm (side of a pixel on Display A)
</code></pre>

<p>Bear with me, as I repeat the number crunching for Display
<code>B</code>:</p>

<pre><code>Display B
Dimensions: 1920x1080 @ 13&#34; (29.5x16.5 sq. cm)
2,073,600 s^2 = 486.75
            s = 0.0153 cm (side of a pixel on Display B)
</code></pre>

<p>The width of a pixel on Display <code>A</code> is <em>double</em> the width of a
pixel on Display <code>B</code>. The area occupied by a pixel on Display
<code>A</code> is <em>4 times</em> the area occupied by a pixel on Display <code>B</code>.</p>

<p><em>The size of a pixel varies from display to display!</em></p>

<p>A 5x11 bitmap font on Display <code>A</code> would be around 4 mm tall
whereas the same bitmap font on Display <code>B</code> would be around
1.9 mm tall. A 11 px tall character on <code>B</code> is visually
equivalent to a 5 px character on <code>A</code>. When you view a
screenshot of Display <code>A</code> on Display <code>B</code>, the contents are
shrunk down by a factor of 2!</p>

<p>So screen resolution is not enough, how else do we measure
size? Pixel Density! Keen readers will realize that the 5<sup>th</sup>
grade math problem we solved up there showcases pixel
density, or, pixels per cm (PPCM). Usually we deal with
pixels per inch (PPI).</p>

<p><strong>Note:</strong> PPI is not to be confused with DPI <sup id="fnref2"><a href="#fn2" rel="footnote">2</a></sup> (dots
per inch). DPI is defined for printers.</p>

<p>In our example, <code>A</code> is a 75 ppi display and <code>B</code> is around
165 ppi <sup id="fnref3"><a href="#fn3" rel="footnote">3</a></sup>.  A low ppi display appears to be
&#8216;pixelated&#8217;, because the pixels are more prominent, much
like Display <code>A</code>. A higher ppi usually means you can view
larger images and render crispier fonts. The average desktop
display can stuff 100-200 pixels per inch. Smart phones
usually fall into the 400-600 ppi (XXXHDPI) category. The
human eye fails to differentiate detail past 300 ppi.</p>

<p><em>So &#8230; streaming an 8K video on a 60&#8221; TV provides the same
clarity as a HD video on a smart phone?</em></p>

<p>Absolutely. Well, clarity is subjective, but the amount of
detail you can discern on mobile displays has always been
limited.  Salty consumers of the Xperia 1 <sup id="fnref4"><a href="#fn4" rel="footnote">4</a></sup> will say
otherwise.</p>

<p>Maybe I will talk about font rendering in another post, but
thats all for now. Don&#39;t judge a font size by its
screenshot.</p>

<div class="footnotes">
<hr/>
<ol>

<li id="fn1">
<p><a href="https://github.com/nerdypepper/scientifica">https:&#47;&#47;github.com&#47;nerdypepper&#47;scientifica</a>&#160;<a href="#fnref1" rev="footnote">&#8617;</a></p>
</li>

<li id="fn2">
<p><a href="https://en.wikipedia.org/wiki/Dots_per_inch">https:&#47;&#47;en.wikipedia.org&#47;wiki&#47;Dots_per_inch</a>&#160;<a href="#fnref2" rev="footnote">&#8617;</a></p>
</li>

<li id="fn3">
<p><a href="https://www.sven.de/dpi/">https:&#47;&#47;www.sven.de&#47;dpi&#47;</a>&#160;<a href="#fnref3" rev="footnote">&#8617;</a></p>
</li>

<li id="fn4">
<p><a href="https://en.wikipedia.org/wiki/Sony_Xperia_1">https:&#47;&#47;en.wikipedia.org&#47;wiki&#47;Sony_Xperia_1</a>&#160;<a href="#fnref4" rev="footnote">&#8617;</a></p>
</li>

</ol>
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        <p>I'm Akshay, I go by nerd or nerdypepper on the internet.</p>
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