45c:0 Correlation to Multi-Angle Spectrophotometers Reply

When selecting a spectrophotometer to use for measuring and comparing color, it is particularly important to use the right geometry for the application. Sphere instruments are preferred for weathering studies and tinting strength for example; 45c:0 is preferred when harmonizing multi-component objects that may contain parts with different gloss levels; and multi-angle is preferred for materials that change appearance based on observation angle such as coatings with metallic or pearlescent pigments. One question that sometimes comes up regarding multi-angle spectrophotometers is whether the 45° measurement angle is the same geometry as a 45/0 or 45c:0 instrument. The answer is yes, and no.

The diagram below shows the geometry of a 45c:0 spectrophotometer:

 

The sample is illuminated circumferentially at 45°, and the reflected light is measured normal to the surface, referred to here as 0°.

This diagram shows the illumination and measurement angles of a multi-angle spectrophotometer:

 

The surface is illuminated at 45° off the normal, and the measurement angles are given in relation to the specular angle (opposite angle to the light source). Thus the 45° measurement angle in a multi-angle spectro corresponds to the 0° measurement angle of a 45/0 spectro. In both cases the sample is illuminated at 45 degrees off the normal, and the color is measured normal to the surface. So what’s the difference? Circumferential illumination.

45c:0 instruments illuminate the sample using a homogeneous 360° ring of light, with all light hitting the sample at 45° off the normal. This eliminates the influence of directionality, meaning the spectro can be oriented in any direction and the results of the measurement will be the same. Multi-angle spectrophotometers do not use circumferential illumination, instead illuminating the sample with a single beam of light from one direction. This is done by design; Multi-angle spectrophotometers are primarily used for measuring painted vehicles such as cars, boats and airplanes, all of which are most often viewed outdoors. Since typical viewing conditions involve light coming from a single direction (the sun) the light source in multi-angle spectros is designed to mimic these viewing conditions. Thus the 45° measurement angle in a multi-angle spectro will produce similar results to a 45c:0 spectro but may differ slightly due to the influence of directionality. Note also that the notation “45c:0” is relatively new, with the “c” meant to indicate circumferential illumination. Many spectros that are labeled as 45/0 or 45:0 also use circumferential illumination.

Panel Match – When Matching to a Standard Isn’t Enough Reply

If you’ve ever used a spectrophotometer for color QC, you probably have a general idea of how it works: measure a standard or use a stored one, then measure the sample. The color difference is calculated, and if that difference falls below a certain level it means the sample is a good color match to the standard, and the product is ready to be shipped. The assumption here is that any parts that are a good color match to the standard will also be a good color match to each other, and this is unfortunately not true. Two samples can be a good match to the standard, both visually and instrumentally, but may not be an acceptable match to each other. This is where the panel match function comes in.

Take a look at the set of three flooring tiles below:

 

 

 

 

 

 

 

Each tile is labeled on the back with a 1, 2, or 3, and when placed in numeric order as above, they appear to be a good color match to each other. But look what happens when we switch Tiles 2 and 3:

 

Suddenly the tiles don’t appear to match! Nothing has changed about the tiles themselves, only the configuration in which we’re viewing them. To understand the cause of the apparent mismatch, we look to the color data:

 

Here we see that Tile 2 is slightly lighter, less green, and less yellow than Tile 1. This trend continues when comparing Tile 3 to Tile 2. However, the color differences between Tiles 1 and 2 are not large enough to be discerned visually, nor are the differences between Tiles 2 and 3. We can see from the table and color plot below that when Tile 2 is used as the standard, Tiles 1 and 3 both fall within tolerance:

 

However, if we set Tile 1 as the standard:

 

Suddenly Tile 3 is no longer within tolerance! This explains why the colors appear to match when lined up in numerical order, but when the order is switched such that we are directly comparing tiles 1 and 3, they no longer appear to match. Now suppose Tile 2 is used as the master standard and Tiles 1 and 3 are production parts. Tile 1 would be measured against Tile 2 and found to be an acceptable match, as would Tile 3. When the customer goes to install Tiles 1 and 3 side-by-side however, they would be upset to find that the tiles do not match! This is why when testing parts that will end up being viewed next to each other, it is necessary to compare those parts not only to the master standard, but to each other as well. This is where the panel match function comes in; by using Organizers in BYK-Gardner’s smart-chart software, when a color reading is taken of a sample to compare to the standard, another sample can be selected to compare the reading with as well. This ensures that not only will production parts match the desired color standard, but will also be a good visual match to other samples when viewed in a real-world setting.

Color Measurement of Solid Colors Reply

Honey Yellow, Raspberry Red, Sapphire Blue or Moss Green are very appealing and descriptive color names. But are you sure that every person means the same color by it? Usually not. How do you clearly describe a color and guarantee that same color over time?

Our color perception is dependent on our individual “taste,” which is influenced by our mood, gender, age, but also the light source used, the viewing environment being light or dark, neutral or colorful as well as our deficiency to exactly remember and communicate one specific color. More…

Transparent Sheets Reply

Light weight and high design flexibility make transparent plastic sheets attractive for use as “organic glass” in many different applications, e.g., noise barriers, green houses, sport arenas, sky domes, solar panels or bus stop shelters. In addition, rigidity and impact resistance of acrylic (PMMA) and polycarbonate (PC) sheets were optimized expanding its usage for safety and architectural glazing as well as for automotive, aircraft, yacht or caravan applications. Depending on the application, the transparency requirements will be very different and need to be objectively controlled – often within very tight specification. More…

byko-spectra lite – economy light booth with premium performance Reply

BYK-Gardner, worldwide partner of the paint and plastic industries for quality control of color, appearance and physical properties, is introducing the new light booth byko-spectra lite. In addition to the well-proven BYK-Gardner light booth range, the lite version with five light sources and compact design creates the standard for critical visual evaluation in laboratory and production. More…

NEW BYK-Gardner Digital Catalog 2016 1

The 2016 BYK-Gardner Catalog with new color, appearance and physical test products, new application stories for trouble shooting, new free services for continuing education, new practical tips how to set tolerances and perform tests including an update on international standards is now available in a downloadable digital format. More…

Free Webinar: The Basic Building Blocks of Color QC June 29, 2017 Reply

Fundamentals of Colorimetry Vividly Explained

Visual color perception is influenced by our individual color preferences depending on our personal experience and memory, varying environmental conditions such as lightness and color, as well as on the deficiency to communicate and document color.

The CIE standardized light source and observer guarantee an objective description of colored objects. Only the use of standardized color instruments with internationally specified color systems can solve the shortcomings of visual perception. More…

Oldest Glossmeter Contest Reply

Do you have an old gloss meter still in use?

It may be the oldest!

BYK-Gardner is running a contest to find the oldest gloss meter still in use. Enter here for your chance to win a new micro-gloss with smart-lab.  Contest ends June 30th 2017.

Gloss meters in the Museum at BYK-Gardner USA. Photo Courtesy of BYK-Gardner USA.

 

 

 

 

 

 

For more information on BYK-Gardner, visit byk.com.

Free Webinar: Color Control of Effect Colors June 1, 2017 Reply

How to measure total color impression of effect colors?

In contrast to solid colors, effect finishes change their color and appearance with viewing angle and lighting conditions. Metallic finishes show a lightness travel depending on viewing angle whereas pearlescent colors also create a color flop. Additionally, special effect pigments exhibit high sparkling effects under direct illumination.

In order to objectively describe the visual impression of effect finishes two different measurement principles are needed. Attend the webinar to learn more! More…

Consistent Quality of Powders and Creams Reply

Eye shadows are produced as powder or creamy product. Colored facial products are available highly viscous lotion or a foundation, which is often finished with a facial pressed powder. Finding the right skin tone takes time and once selected it is expected to be the same at each purchase.

Color consistency is a key quality criterion for a successful product with a long lifetime. Powders, pastes and liquids can either be measured in mass or in case of lower viscosity products as drawdowns on test charts. In both cases a noncontact measurement technique will be the preferred method since this technique correlates best with how the consumer perceives the final product in the store. More…