<p>I am trying to measure the reflectance% of a surface (it is made of Teflon and is very white). I am using a line spectrometer. I believe the piece can replace an expensive Spectralon for some experiments. To show that it has a quite acceptable reflectance, I need to draw its reflectance plot at different wavelengths similar to the chart presented with Spectralon. See the below image.
<a href="https://i.sstatic.net/2MAyS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2MAyS.png" alt="Reflectance spectrum of Spectralon"></a></p>

<p>I had a look at different pieces of literature and I found out with two spectrum recordings of direct light source facing the spectrometer and illuminating the surface with the light then recording its reflection I am able to calculate the reflectance. To do so, I normalized the two readings with respect to the exposure times and I divided the two signals (surface spectrum divided by direct illumination spectrum) and this graph is obtained.
<a href="https://i.sstatic.net/TMgh1.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/TMgh1.jpg" alt="Reflectance"></a></p>

<p>I also attached the Digital Number read by camera here.
<a href="https://i.sstatic.net/k49xF.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/k49xF.jpg" alt="Teflon Digital Number normalized by the exposure time"></a>
<a href="https://i.sstatic.net/FWnBi.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/FWnBi.jpg" alt="Digital Number from direct light"></a></p>

<p>The detail of the experimental setup is as follows:
1- The camera angle is 45 degrees with respect to the surface and the illumination light is facing 45 degrees to the surface.  </p>

CC BY-SA 4.0
2020-06-02T17:38:30.270Z
I am not really sure if this is the right place for your question since this site is about generating computer graphics and not about measurement techniques. I don't say that it doesn't fit here, I am just not sure if this community can provide you with an answer.
wychmaster
CC BY-SA 4.0
2020-06-03T04:18:31.763Z
Keyvan, I suggest to post your question in Radiance forum. Though it's not a specific software question, the Radiance community is likely to give you the answer.
ali
CC BY-SA 4.0
2020-06-03T04:18:43.790Z
Here: https://discourse.radiance-online.org/
ali
<diffuse>
How to measure the reflectance of a material without using a Spectralon
Keyvan Jaferzadeh
# How to measure the reflectance of a material without using a Spectralon

(Asked by: username_0 on 2020-06-02)

I am trying to measure the reflectance% of a surface (it is made of Teflon and is very white). I am using a line spectrometer. I believe the piece can replace an expensive Spectralon for some experiments. To show that it has a quite acceptable reflectance, I need to draw its reflectance plot at different wavelengths similar to the chart presented with Spectralon. See the below image.
[![Reflectance spectrum of Spectralon](https://i.sstatic.net/2MAyS.png)](https://i.sstatic.net/2MAyS.png)

I had a look at different pieces of literature and I found out with two spectrum recordings of direct light source facing the spectrometer and illuminating the surface with the light then recording its reflection I am able to calculate the reflectance. To do so, I normalized the two readings with respect to the exposure times and I divided the two signals (surface spectrum divided by direct illumination spectrum) and this graph is obtained.
[![Reflectance](https://i.sstatic.net/TMgh1.jpg)](https://i.sstatic.net/TMgh1.jpg)

I also attached the Digital Number read by camera here.
[![Teflon Digital Number normalized by the exposure time](https://i.sstatic.net/k49xF.jpg)](https://i.sstatic.net/k49xF.jpg)
[![Digital Number from direct light](https://i.sstatic.net/FWnBi.jpg)](https://i.sstatic.net/FWnBi.jpg)

The detail of the experimental setup is as follows:
1- The camera angle is 45 degrees with respect to the surface and the illumination light is facing 45 degrees to the surface.

**Tags:** diffuse

> **Comments:**
> **username_1**: I am not really sure if this is the right place for your question since this site is about generating computer graphics and not about measurement techniques. I don't say that it doesn't fit here, I am just not sure if this community can provide you with an answer.  
> **username_2**: username_0, I suggest to post your question in Radiance forum. Though it's not a specific software question, the Radiance community is likely to give you the answer.  
> **username_2**: Here: https://discourse.radiance-online.org/  

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## 0 answers

