<p>In PBRT-V3, the light has following spectrum in scene file(Note that the scene file is not come from PBRT itself):</p>
<pre><code>&quot;spectrum&quot; [400.0 0.0 500.0 8.0 600.0 15.6 700.0 18.4]
</code></pre>
<p>then it's converted to following RGB in C++:</p>
<pre><code>&quot;rgb&quot; [20.7467213 10.8233843 2.76458955]
</code></pre>
<p>is this correct? Why the RGB value exceeds 1? Whether this is used to indicate light intensity?</p>

CC BY-SA 4.0
2021-08-10T04:43:42.887Z
HDR lights or as you said it's basically color*intensity in a single rgb triple I guess
gallickgunner
CC BY-SA 4.0
2021-08-10T12:55:32.727Z
Color does not really jave a upper limit. What you see on screen is normalized for the screen device. But that does not mean a blue, brighter more intense blue does not exist. Just not what your monitor can show.
joojaa
<pbrt-v3>
Why RGB value bigger than 1 when convert from spectrum in PBRT-V3
Chris Guo
# Why RGB value bigger than 1 when convert from spectrum in PBRT-V3

(Asked by: username_0 on 2021-08-10)

In PBRT-V3, the light has following spectrum in scene file(Note that the scene file is not come from PBRT itself):

```
"spectrum" [400.0 0.0 500.0 8.0 600.0 15.6 700.0 18.4]

```

then it's converted to following RGB in C++:

```
"rgb" [20.7467213 10.8233843 2.76458955]

```

is this correct? Why the RGB value exceeds 1? Whether this is used to indicate light intensity?

**Tags:** pbrt-v3

> **Comments:**
> **username_1**: HDR lights or as you said it's basically color*intensity in a single rgb triple I guess  
> **username_2**: Color does not really jave a upper limit. What you see on screen is normalized for the screen device. But that does not mean a blue, brighter more intense blue does not exist. Just not what your monitor can show.  

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## 0 answers

