Ransen's Lighting And Color Blog

The OXL file format is an XML based format which contains the photometry (like an IESNA .IES or an Eulumdat .LDT) file format, but adds much much more. The OXL file format is open and free to use by any company. Here's an overview of what an OXL file can contain: As you can see there must be a photometry, and to that you can any or none of the following things: PDF data sheet. Photo. Spectral data. 3D model (a simplified 3D model is ideal for Revit applications). So when a customer wants details about your luminaire, you don't need to send him N files, just a single OXL file. Now I think examples are easier to understand than formal definitions, so here is what the start of an OXL file looks like: Because Eulumdat and IESNA files are so constricted, some companies " expand and re-interpret " them, with non standard "extensions" which only a few programs (mostly company internal programs) understand. These e

This article is a bit of extra help for this one (on CIE88 2004). We know that we need to arrive at an internal tunnel luminance Lin, and we know we start at the formula for calculating the curve is the one given above, Ltr.  Time and distance are related by the fixed velocity, v, of the tunnel project. If we get the time taken to go through the transition zone we can easily get the length of the transition zone. Re-arranging the original equation... So you can calculate d, the length of the transition zone, from these three things: the project velocity the threshold luminance the internal luminance. (Thanks to Bui Duc Han for correcting an error in a previous version of the steps above.)

( See also CIE88 2004 ) Here are the Luminance Grids for calculating L seq . of all three standards: In all three standards there are 9 rings and 12 (radial) sectors. The UNI11095 2011 grid weights the upper and lower fractional sections by their reduced area.  The CIE88 2004 has the "tallest" grid but the uppermost and lowermost areas are not used in the calculation, as they are considered to be outside a normal person's field of view.  The UNI11095 2003 grid did not take into account the fact that the upper and lower areas are smaller, but it did have a wider aspect ratio. UNI11095 2011 introduced a maximum curve above the minimum curve, presumably to encourage energy saving as well as luminous uniformity :

Though BUG ( IES TM-15-11, Addendum A) is quite hard to do, it is easy to understand, it gives you numbers for the "amount of light", wasted in various non-useful directions. B stands for Backlight, light thrown back away from the road. U stands for Uplight, light leaking skywards and causing light pollution. G stands for Glare, how much light is wasted shining directly into (a relatively distant) the driver's eye. The output of the luminaire is divided into several sub-zones:   Light issuing from High to Very High (H and VH) zones can cause glare from a distance and is anyway wasted light. These zones, both foward and back are used for the G rating. These are the red areas in the schematic below: Light sent to the B ack away from the road and towards the sidewalk (purple in the above diagram) is not useful fo

I was watching QI (a BBC program of semi-serious questions and semi-serious answers, QI = Quite Interesting) and one of the questions which came up a few weeks ago was about imaginary colors. They messed up the graphics quite badly like this: So colors between deep blue and purple-red are not supposed to exist. QI did not explain why. I've seen in some textbooks that these colors are described as mysterious or anomolous. In the textbooks  this diagram is used... ...which at least gives a bit more "explanation" of why they should not be visible. According to some people, since they are on that strange lower edge, and not on the "spectral edge" they are therefore non-existent colors. (I found the reasoning to have the same weight as those who say "science says bumble bees should not be able to fly, but they can, so science is wrong!" It is clear to anyone with half a brain that bumble bees are not shaped like aircraft, are lighter and les

The standard is officially called "Guide for the Lighting of Road Tunnels and Underpasses" and this article is about the 2004 version, which is currently in use. It replaces the 1990 version.  This article is a user friendly summary of the standard and ignores some details, for example daylight screens and emergency lighting. I'll just be looking mainly at the requirements for lighting tunnels in the daytime, a large part of which concerns the effect of the luminance of the areas surrounding the tunnel entrance. For an explanation of what luminance means , this book wi ll help you: You may have noticed that as you approach a long tunnel in bright sunlight the entrance often seems like a black hole:     In these cases, if there was an obstacle (like a stopped car or a drunk pedestrian) just a few meters into the tunnel you wo