{"id":360,"date":"2015-03-29T09:32:19","date_gmt":"2015-03-29T13:32:19","guid":{"rendered":"https:\/\/designinglight.com\/?p=360"},"modified":"2015-03-29T10:13:24","modified_gmt":"2015-03-29T14:13:24","slug":"with-leds-knowledge-is-power","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=360","title":{"rendered":"With LEDs, Knowledge is Power"},"content":{"rendered":"

I\u2019ve been hired to review an architect\u2019s lighting design and then design an appropriate control system. The fixtures selected are all LED products by a manufacturer that falls into the high-end residential\/economy commercial range of quality and price. The cut sheets are extremely frustrating. After nearly a decade of LED lighting, and with all of the progress the industry has made in setting standards so that designers and specifiers know what they\u2019re getting, this manufacturer still tells us nothing. What basic information is missing?<\/p>\n

\u00a0Lamp life.<\/strong> The only information even remotely connected to lamp life is the statement that the fixture is covered under a five-year warranty. There\u2019s nothing else. Not a word. How much light, compared to initial output, can we expect at that five-year mark? \u00a0We have no idea.<\/p>\n

LEDs do not fail like other lamps do. \u00a0They gradually dim as they age. \u00a0At what point is the light output so low that we’d say the lamp is no longer useful? \u00a0Right now the answer is when the light output has fallen to 70% of the initial output (often referred to as L70), although many designers prefer to use 80% of initial output (referred to as L80). \u00a0This is calculated using a procedure developed by the IES and designated as LM-80 (details are here<\/a> and here<\/a>). \u00a0What we want, at a minimum, is the IES LM-80\u00a0calculation of lamp life to 70% of initial output. L80 data would be even better.<\/p>\n

\u00a0Warranty.<\/strong> The warranty is not on the manufacturer\u2019s web site so, although we\u2019re told that it is good for five years, we have no information about what is covered and what is excluded.<\/p>\n

\u00a0LED manufacturer<\/strong>. With all other lamp types the designer chooses the exact lamp for the project. Criteria such as initial lumen output, mean lumen output, lamp life, color temperature, CRI, and the manufacturer\u2019s reputation for quality are all valid considerations. We have standards that allow designers to make valid comparisons between LED products, too, but we can do that only if that information is generated and shared. I suspect that this fixture manufacturer uses LEDs from a several manufacturers based on the best price available, and that the performance of those LEDs varies widely.<\/p>\n

\u00a0Color consistency.<\/strong> The cut sheet says that the standard applied to their LED selection is, \u201cminimum 3-step color binning.\u201d We are left to infer that means three-step MacAdam Ellipses. \u00a0A one-step MacAdam Ellipse describes a region on a chromaticity diagram or color space where the edges of the ellipse\u00a0represent a just noticeable difference from the color at the center (additional information on MacAdam Ellipses is here<\/a> and here<\/a>).\u00a0\u00a0The data is usually plotted on the CIE 1931 (x, y) chromaticity diagram. \u00a0The diagram below shows 10-step MacAdam Ellipses.<\/p>\n

\""CIExy1931<\/a>
“CIExy1931 MacAdam”. Licensed under CC BY-SA 3.0 via Wikimedia Commons – http:\/\/commons.wikimedia.org\/wiki\/File:CIExy1931_MacAdam.png#\/media\/File:CIExy1931_MacAdam.png<\/figcaption><\/figure>\n

 <\/p>\n

The color variation within a three-step ellipse would be noticeable to over 99% of the population. \u00a0Worse, though, is that a three-step ellipse is the minimum<\/em>, not the maximum. Knowing this, the designer should have no expectation of color consistency from one fixture to another.<\/p>\n

\u00a0Photometrics.<\/strong> The cut sheet contains no information about the optical performance of the fixture. IES files are available, but it\u2019s very difficult to look at the array of numbers and understand performance, which is why the good manufacturers include photometric information on their documentation, including candlepower distribution curves and CU tables.<\/p>\n

Part of my review will be pointing out the lack of data about the specified fixtures and recommending several alternates by manufacturers who provide the information necessary to evaluate their products.<\/p>\n","protected":false},"excerpt":{"rendered":"

I\u2019ve been hired to review an architect\u2019s lighting design and then design an appropriate control system. The fixtures selected are all LED products by a manufacturer that falls into the high-end residential\/economy commercial range of quality and price. The cut sheets are extremely frustrating. After nearly a decade of LED lighting, and with all of … Continue reading With LEDs, Knowledge is Power<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[18,19,10],"tags":[30,24,49],"class_list":["post-360","post","type-post","status-publish","format-standard","hentry","category-design","category-lighting-profession","category-luminaires","tag-led","tag-led-color","tag-specifications"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-5O","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":965,"url":"https:\/\/designinglight.com\/?p=965","url_meta":{"origin":360,"position":0},"title":"Soraa Profiles Jason Livingston and Studio T+L","author":"Jason Livingston","date":"May 14, 2019","format":false,"excerpt":"Jason Livingston, principal of Studio T+L, illuminates theaters and other unique spaces with ingenious lighting designs. 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