> For the complete documentation index, see [llms.txt](https://docs.coraye.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coraye.com/colors/capture-a-light.md).

# Capturing a Light

### 1. Prerequisites

This function needs a spectrophotometer to work (Konica Minolta MYIRO, XRite Eye One Pro 1, 2 or 3)

{% tabs %}
{% tab title="Booth" %}
![](/files/-LjCd7c8rcQdm_sxPFsO)
{% endtab %}

{% tab title="Room" %}
![](/files/-LmofTkvXFPoBw20MPny)
{% endtab %}
{% endtabs %}

### 2. How to use Illum Reader

Click on the icon "Create Light" in the toolbar of Coraye

![](/files/-MF59Nj5vmbpARxsQbsi)

Make sure your spectrophotometer is connected. When the "Read target" window appears, click on "I'm ready".

![](/files/-MF5A2En54cgJDpYBZq_)

A new window will appear to calibrate your spectrophotometer.

![](/files/-MF5ALd_OBGWYGvJ9eQy)

Put the spectrophotometer into the calibration position\
Then click on the Start calibration button.

{% tabs %}
{% tab title="Konica Minolta MYIRO" %}
![](/files/-MF1kORVlnT-Mcw_W-wL)
{% endtab %}

{% tab title="XRite I1 Pro" %}
![Calibration position](/files/-LjCdWIXz4eH5y4Pt3QC)
{% endtab %}

{% tab title="XRite I1 Pro 2" %}
![](/files/-MBmacetMFAnXH6pkv2I)

Then click on the **Start calibration** button.
{% endtab %}

{% tab title="XRite I1 Pro 3" %}
![](/files/-MF1l1t-XToZ7Cg0JqwT)
{% endtab %}
{% endtabs %}

When the calibration is done, a new window will appear.

![](/files/-MF5KbWNUT3V0f2WmV3p)

{% hint style="warning" %}
Be aware, you have to use the cap to read the light with the Konica Minolta MYIRO, I1 Pro 1, 2 & 3.
{% endhint %}

{% tabs %}
{% tab title="Konica Minolta MYIRO" %}
![](/files/-MF5JxL5wux6VaaJk7EE)
{% endtab %}

{% tab title="XRite I1 Pro" %}
![](/files/-LmoXixsOSnDVKRd4zzK)
{% endtab %}

{% tab title="XRite I1 Pro 2" %}
![](/files/-LmoY3NNcXpfsmb5HDiP)
{% endtab %}

{% tab title="XRite I1 Pro 3" %}
![](/files/-MF5Jkh5c4fFMGprSj3l)
{% endtab %}
{% endtabs %}

To capture the light, it is now sufficient to measure directly with the spectrophotometer. \
Successive measurements will be displayed one below the other.

![](/files/-MF5IrbJW0ts_Id72sk1)

You can make multiple measurements and rename them as you like.

![](/files/-MF5Ms_MKdCkxsgcviCq)

When your measurements are finished, click on **Save and quit**.\
Yours lights samples will be add into the left column.

![](/files/-MF5NDRrB-j0wuPC7UdL)

### 3. How to manage yours Lights samples

Click right on the color to **Rename**, **Duplicate** and **Delete**.\
**Export** option allow saving the color as a .sp file with spectral data.\
These .sp files are useful to share and backup yours light samples.

![](/files/-MF5Ojgl4w_j1Ww7aUs8)

Measures can be export as a .sp file, to be saved on your hard drive.

### 4. What are the values associated with the measured sample?

When we read a light, we can get information like [CCT, CRI, ](https://en.wikipedia.org/wiki/Color_temperature)Ra, Brithness, Lab and x,y

![](/files/-MF5TQO5IvFcXzSwcr-w)

{% hint style="info" %}
The [CIE](https://en.wikipedia.org/wiki/International_Commission_on_Illumination) [color rendering index](https://en.wikipedia.org/wiki/Color_rendering_index) (**CRI**) is a method to determine how well a light source's illumination of eight sample patches compares to the illumination provided by a reference source. Cited together, the CRI and CCT give a numerical estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is.\
\
**CRI is a quality index for evaluating an illuminant. It is expressed as a percentage. the higher the value, the better the quality of the illuminant.**
{% endhint %}

{% hint style="info" %}
The **color temperature** of a light source is the [temperature](https://en.wikipedia.org/wiki/Temperature) of an ideal [black-body radiator](https://en.wikipedia.org/wiki/Black-body_radiation) that radiates light of a color comparable to that of the light source. Color temperature is a characteristic of [visible light](https://en.wikipedia.org/wiki/Visible_light) that has important applications in [lighting](https://en.wikipedia.org/wiki/Lighting), [photography](https://en.wikipedia.org/wiki/Photography), [videography](https://en.wikipedia.org/wiki/Videography), [publishing](https://en.wikipedia.org/wiki/Publishing), [manufacturing](https://en.wikipedia.org/wiki/Manufacturing), [astrophysics](https://en.wikipedia.org/wiki/Astrophysics), [horticulture](https://en.wikipedia.org/wiki/Horticulture), and other fields. In practice, color temperature is meaningful only for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e., light in a range going from red to orange to yellow to [white](https://en.wikipedia.org/wiki/White) to blueish white; it does not make sense to speak of the color temperature of, e.g., a green or a purple light. Color temperature is conventionally expressed in [kelvins](https://en.wikipedia.org/wiki/Kelvin), using the symbol K, a [unit of measure](https://en.wikipedia.org/wiki/Unit_of_measure) for absolute temperature.

Color temperatures over 5000 K are called "cool colors" (bluish), while lower color temperatures (2700–3000 K) are called "warm colors" (yellowish). "Warm" in this context is an analogy to radiated heat flux of traditional [incandescent lighting](https://en.wikipedia.org/wiki/Incandescent_light) rather than temperature. The spectral peak of warm-coloured light is closer to infrared, and most natural warm-coloured light sources emit significant infrared radiation. The fact that "warm" lighting in this sense actually has a "cooler" color temperature often leads to confusion.[\[1\]](https://en.wikipedia.org/wiki/Color_temperature#cite_note-1)
{% endhint %}

![](/files/-LmsIAQPj61iwyT_gosv)

To save your measure, click right on the measured light into the left bar, and select **Export** to save as a .sp file.\
As you see, you can also Rename, Duplicate or Delete the file when you click left on it.

### 5. Control your booth or your viewing condition

IllumReader can be useful to check uniformity, the color temperature and the light intensity into a booth, to check the conditions for viewing proofs, objects and prints. \
\
In the field of graphic arts, ISO standards have been defined to standardize the visualization conditions of prints.\
\
Knowing how to master one's light knows how to master one's color.

{% tabs %}
{% tab title="Viewing condition" %}
![](/files/-LmofTkvXFPoBw20MPny)
{% endtab %}

{% tab title="P1 Critical Comparison" %}
![Standard viewing condition ISO 3664: 2009 P1](/files/-LjCd7c8rcQdm_sxPFsO)
{% endtab %}

{% tab title="P2 Practical Appraisal" %}
![Standard viewing condition ISO 3664: 2009 P2](/files/-LmsW8Kgsb1hbe_FtuiP)
{% endtab %}
{% endtabs %}

{% hint style="info" %}
ISO 3664:2009 – VIEWING CONDITIONS\
\
 **Light source**\
 • Relative spectral power distribution must match CIE illuminant D50\
 • UV energy must meet CIE illuminant D50 (correlates to M1 within ISO 13655)\
\
**Two levels of light intensity conditions**\
 • P1 Critical Comparison: e.g. two prints: **illuminance 2000 ± 500 Lux**\
 • P2 Practical Appraisal: less critical comparisons e.g. hardcopy to softproof: **500 ± 125 Lux** or exact illuminance adjustment of light booth to monitor \
\
**Further definitions**\
 • **Homogenity (Control over 9 zones in your booth)**\
 • Surrounding: neutral gray diffuse surface\
 • Viewing angle to avoid glare
{% endhint %}

### 6. Light measurement can be use to calculate an Icc profile.

{% content-ref url="/pages/-LjRTIyoM9ZfJ\_hs62lH" %}
[Create a profile from a standard reference](/printer-management/how-to-create-a-media-profile.md)
{% endcontent-ref %}

### 7. Show yours reflectance curves in the Spectral Viewer.

It could be useful to compare reflectance curves of your color sample with a spectral curve of a specific light to understand the metamerism effect.

If you need to display the spectral curve of your measured light, you can use the [Spectral Viewer](https://docs.coraye.com/visualization-modules/spectral-viewer)

{% content-ref url="/pages/-LjCcaw4PDRzF6X\_8gFT" %}
[Spectral viewer](/visualization-modules/spectral-viewer.md)
{% endcontent-ref %}