Lesson 2 - Value and LRV Transcript. In this lesson we're going to learn about TWO of The Four Pillars of Color, Value and LRV.

Transcription

1 Lesson 2 - Value and LRV Transcript In this lesson we're going to learn about TWO of The Four Pillars of Color, Value and LRV. Let's kick this off with the definition of value. Value is simply a scale between black and white. So, lightness, Light Reflectance Value which is also known as LRV, and Munsell Value all fit under the term Value because each of these color attributes can be illustrated using a scale with black on one end and white at the other with any number of steps in between. For example, the CIE Lightness scale runs 0 to 100 and the Munsell Value Scale has 10 steps. The hue value/chroma chart from your Munsell Learning Kit that we'll be using in the assignment this week has only 9 steps because they didn't include 0 absolute black and 10 absolute white. Probably because absolute black and white do not exist outside of a mathematical color model. Throughout this lesson we're going to discuss how these attributes are related and how they differ. If you recall, in the executive summary of color spaces from the last lesson, you learned that CIELAB and CIELCh were modeled after the Munsell Color System. Which is why I was able to combine LCh hue angle with Munsell hue families to create The Color Strategist Color Wheel. Well, that correlation between CIELAB, LCh and Munsell applies to value too and I have a super handy shortcut coming up in this lesson. But first let's talk about this week's assignment using another exercise from your Munsell Learning Kit. You'll need the envelope of 24 chips marked "HVC" and the Hue Value/Chroma Chart.

2 The last time we used this chart we completed the hue family portion. Now we're going to complete the value scale. Make sure you have good lighting for this exercise. If you don't have an OttLite I recommend buying one. Michael's is a good source because they always have a coupon and they have several styles and price points to choose from. You should have 13 chips left in your envelope and you'll need the 7 neutral gray chips to complete the value scale. This is what the completed assignment should look like. Once you complete your chart, snap a picture and upload it in the lesson. If you don't have your Munsell Learning Kit yet, just upload any picture so you can keep moving, and then when you get your kit, come back to the lesson and up load your completed value scale assignment. Since the CIE lightness, or L* value in CIELAB and LCh was designed to model the Munsell system, there's a shortcut you can use. I'm going to use a section from my Master List spreadsheet to show you how this works and we'll get back to this in a minute. In the last lesson you learned how to use LCh and The Color Strategist Color Wheel to quickly determine the hue family a color belongs to - I said it was the quick and dirty method compared to using CIELAB values to calculate a more accurate Munsell hue, value, chroma notation. What I'm going to show you now is a shortcut to quickly estimate the Munsell Value for a color using CIE lightness. You already know how to use easyrgb.com and your Color Muse to get CIELAB and LCh color values. And, of course, you know the L in CIELAB and LCh is the numeric value for the lightness of a color. Sometimes that L is written as L* or CIE L*. So, you know exactly where and how to get the CIE Lightness value for a color. Here's the shortcut you need to know. A very useful and accurate general rule is the Munsell value of a color can be obtained from its CIE Lightness value by simply dividing by 10.

3 I've rounded the numbers in the Lightness and Value columns so it's easier to see how this math trick works to quickly convert CIE Lightness to a Munsell Value notation. The reason why this is so useful is because the CIE Lightness scale runs from 0 to 100 and it's hard to estimate in your head what a lightness of 50, for example, looks like. However, if you divide that lightness value of 50 by 10 to get a Munsell Value of 5, it's much easier to visualize and manage. Basically, it's this (Colorography with Munsell scale) vs. this (CIE Lightness scale). The scale with only ten steps is much easier to visualize and manage when comparing the value of different colors. And that's the reason why this color hack is so useful. Let's talk about how and why it's possible to simply divide by ten to toggle between CIE Lightness and Munsell Value. The difference between CIE Lightness, Light Reflectance Value and Munsell Value could be a long and very technical discussion. For example, this excerpt from a color science book that explains how Munsell Value is related to CIE Lightness: The Munsell value (V) scale is related to CIE luminance factor (Y) by a complex fifth degree polynomial equation called Judd's polynomial as follows (Newhall, 1940): Y = V V V V V5 The equation was devised by Judd with measurements based on the use of magnesium oxide, and assigned a value of absolute reflectance of for 45 /0 illumination and viewing. Source: Colour Measurement: Principles, Advances and Industrial Applications, Edited by M. L. Gulrajani

4 Although we don't go into color math like the fifth polynomial equation mentioned here, we do dig deeper into the topic of value in general in Course 1. But for this course, Course 2, I'm going to give you an executive summary kind of overview - just like what I did for color spaces in the Hue and Hue Families Lesson. We have to start with luminance. Because lightness, LRV and Munsell Value are derived from luminance. Luminance is part of the color DNA that's captured when a color is measured with a device like a spectrophotometer. The CIE name or label for luminance is CIE Y tristimulus value or just CIE Y. Luminance, CIE Y, LRV, lightness and Munsell Value are all related mathematically. Here's how they break down: Luminance, LRV, and CIE Y are the same thing. This value is a quantity - a quantity of light that a color reflects and conversely absorbs. Luminance speaks to how bright a color literally *is* and it's represented on a scale of percentages. My LRV scale is made up of suns because the suns represent a quantity of light. Lightness is different because it's a perception. Lightness is a perception of luminance. Lightness answers the question how bright does that luminance *look*. Lightness is represented on simple numeric scale --- like the Munsell value scale. Because lightness is about how bright and light a color looks, I chose to illustrate the steps from darkest to lightest on my value scale with an icon that looks like an eye. Not so complicated once you understand it is it? Because it is so simple and because LRV and lightness values are so rich with information about how a color will respond to the light and how it will be

5 perceived, I include both value scales in the Colorography infographics I make - they're an at-a-glance graphic that draws a picture of everything you need to know about a color. In the previous lesson, you learned how to use easyrgb.com and your Color Muse to get CIELAB and CIE LCh values that include lightness. In the next part of this lesson, I'm going to show you how to get light reflectance values. Even though LRV for paint colors is printed in the index of most major brand's fandecks, it's good to know how to get an LRV reading that's accurate enough to use for reasonable guidelines. The first resource we're going to explore is easyrgb.com so let's go there now. How to Find LRV on EasyRGB.com 1. From the main menu, type in the name of the color you want to find the LRV for. 2. Your color will appear directly below highlighted in red 3. Click on your color. 4. Click Compare. 5. Find your color on this new page and click on it. 6. A new menu will pop up, choose Convert. 7. A page of color data for your color will pop up. 8. Find the section with XYZ and Yxy. As you learned earlier in this lesson CIE Y is another name for LRV. The capital Y in XYZ and Yxy is the Light Reflectance Value for your color. Please note that the capital Y in CMYK is not LRV. The Y in this case stands for yellow ink as in Cyan, Magenta, Yellow and Black. Only the capital Y in XYZ and Yxy is light reflectance value. How to Find LRV using the LRV Guru App and Color Muse 1. Download the LRV Guru app from itunes. 2. Open the app

6 3. Click the button on your Color Muse to get a flashing blue light 4. Choose Connect from the app's main menu 5. Choose a Color Sensor by tapping on ColorMuse-(your device's ID number) 6. Make sure the white calibration cap is on and tap in the middle of the calibration paragraph 7. Choose Compare 8. A Dual Scan Screen pops up 9. Place Color Muse on your first target color and tap Scan Place Color Muse on your second target color and tap Scan The LRV will display for each color as well as LCh values. The contrast ratio, or the difference between the two Light Reflectance Values will display below the colors. If the difference is displayed in black, that means it passes the general guideline of a 70% contrast ratio. If it appears in red, that means it did not pass. 70% is a general guideline for the contrast ratio of two colors. The guideline is used in various color specification standards. For example, signage; the letters of a sign must have adequate contrast compared to the background. Later in the course we'll explore some other applications using Light Reflectance Values. So, that's how you get the LRV for any color you want. Thanks everyone, I hoped you enjoyed this lesson about Value and LRV.