White LED light has different shades and when a lighting installation is all the same shade then LED color consistency is very high. When color consistency is poor, many shades can be seen with the naked eye, as in the image below:
This is an extreme of cases, with LEDs or luminaries having all the shades of white mixed up: warm white, pure white and cold white in one installation.
However, the same phenomenon exists for products marketed as warm white, pure (natural) white or cold white.
While there is no consensus, warm white light for LEDs has a value of 2500K-4000K on the color temperature scale, pure white 4000K-5000K and cold white 5000K-10.000K.
For our explanation, we will focus on warm white LEDs, although it can apply to pure and cold white.
Warm white LEDs, as with all manufactured products, have material and process variations that yield products with corresponding variation in the shade of white light emitted. For example, Nichia warm white LEDs just out of the production line can have a color temperature between 2580K and 4260K. If directly integrated into strips or luminaries, these color inconsistent products will be generally unusable.
To prevent the issue above, LEDs are sorted and grouped in batches known as "Chromaticity Bins". Nichia, as a LED manufacturer, groups warm white LEDs in four Bins which is perfect for our easy explanation.
Nichia LEDs chromaticity explained with a deck of cards
Let's link the Nichia Bins with the symbols from a deck of cards:
- SW27 - Clubs (2580K-2870K)
- SW30 - Diamonds (2870K-3220K)
- SW35 - Spades (3220K-3710K)
- SW40 - Hearts (3710K-4260K)
This is the most basic sorting and, as with a deck of cards, there are more important details to follow. Each symbol from the deck has a number of cards, and if the symbol is the BIN then the cards represent the sub-bins. For Nichia the number of sub-bins (cards) can be up to 16.
From Chromaticity Bins to Macadam Ellipses
Macadam Ellipses relates to how LEDs with certain manufacturer sorted bins can be purchased. Common sense would say that if a deck of cards symbolizes our choice of LED Bins and Sub-Bins, we then can pick any card we like for our order.
That is not true, we can never pick one card from the Bin Deck. Furthermore, we cannot even pick two cards. The minimum we can do is choose the symbol (Diamonds, for example) and ask to receive three cards with this symbol from the deck. This is called Macadam Ellipse LED sorting and can be 7-step, 5-step, 3-step or without sorting.
The Macadam Ellipse LED sorting of LED Chromaticity Bins explained with a deck of cards
1. 7-step MacAdam Ellipse Sorting = Choose the card symbol and ask for 7 cards in order
Let's say we choose the Clubs cards (for Nichia that would be bin SW 2580K-2870K).
Our 7-step delivery will consist of seven cards of random selection with the condition they fall within a sub set of seven consecutive cards from the deck.
Examples of combinations from the cards below: 7-7-7-10-Q-Q-K, 7-9-9-J-J-KK, 7-10-10-10-Q-K-K and many more...
2. 5-step MacAdam Ellipse Sorting = Choose the card symbol and ask for 5 cards in order
Again, if choose the Clubs cards (SM273 2580K-2870K) our 5-step delivery will consist of five cards of random selection with the condition they fall within a sub set of five consecutive cards from the deck.
For example: 7-7-9-10-J, 7-8-10-10-J, 7-9-10-10-J.
For many projects, this sorting is satisfactory. Usually a 5-10% price increase results from 5 step MacAdam Ellipse Sorting.
3. 3-step MacAdam Ellipse Sorting = Choose the card symbol and ask for 3 cards in order
To continue our example, from the Clubs cards (SM273 2580K-2870K) our delivery will consist of three cards of random selection with the condition they fall within a sub set of three consecutive cards from the deck. With this choice, the differences in the color temperature will almost be invisible.
Examples: 9-10-J, 9-9-J...
3-step MacAdam Ellipse sorting is in some cases offered with a 20-30% higher price. This choice could be further be upgraded with asking for the cards in the middle of the deck.
4. No sorting, choose the card symbol only (Bin Only)
The most basic, used of choices and with the lower cost. For example, we choose the Clubs cards (SW 2580K-2870K). Our delivery will consist of a totally random number and set of Clubs cards. Before taking this choice, we must be sure our project will not suffer, as the differences in the color temperature will be very visible.
This choice is usually good for street lighting or Christmas lighting.
At Lumistrips we use LEDs with 3-step MacAdam Ellipse sorting in all our products, so you will have the best color consistency possible and not worry about multi-shaded lighting of your project. We also offer many choices of color temperature, for example our LinearZ modules: