"Candelas Lumens and Lux" introduction to lighting  terms and calculations
"Candelas Lumens and Lux" introduction to lighting  terms and calculations




How to make a Sollner diagram

First let me explain a simplfied Sollner (sometimes written "Soellner") diagram like the one shown below:

Explnation of sollner diagram

Notice the two eye icons on the left of the image. They indicate the angle you would have to look at to see the luminaire from where you are sitting in the room (because Sollner imagined people at desks in offices as his standard situation).

You can read off the glare of a luminaire at various angles. Glare is considered from gamma=45 to gamma=85. Glare is intensity / apparent area. This means it is quite complicated to calculate because not only does the intensity change with gamma, but so does the apparent area of the light emitting surface:

Glare changes with apparent atrea which changes with angle

If the line from the luminaire to your eye is at 45 you are probably visibly aware of the light fitting. Less than 45 and the light is shining more on the top of your head rather than into your eye. At 85 you are further away from the light, but not so far as to be unaware of any glare. If there is bad glare at 85 and you are sitting at the back of the class, then you may not be able to see the whiteboard the teacher is writing on.

For more details about how to read Sollner diagrams, and much much more, read the book Candelas Lumens and Lux:

Remember that you need not just the polar diagram but also the apparent luminous area from various positions in the office to create a Sollner diagram. As I mentioned before, when you think of glare of a luminaire from various points of view it is quite hard to visualise the relationship between luminous intensity (which changes with angle) and apparent area (which also changes with angle).

Sollner is a good way of combining both variables into a single curve.

Roughly speaking if all the curve is in the left half of the diagram there will be low glare at all angles. If all the curve is on the right side of the diagram there will be high glare at all angles.

Low Glare Sollner Diagram

Note that there is a bit more detail (explained in the book) compared with the simplified Sollner diagram at the top of this page. Also note that there are two lines, the longitudinal and the transversal. If you are sitting in a classroom and from where you are sitting the strip lighting is parallel with the line between your eyes, then that is the transversal view of the luminaires. If the strip lighting is "going away from you" then that is the longitudinal view.

If you use PhotoView from OxyTech you can also have multiplane Sollner diagrams, not just from C0 and C90 plane angles. Simply choose the planes you want to see and voila!

Multiplane Sollner Diagram


The book Candelas Lumens and Lux has chapters on luminance and glare (i.e. what Sollner diagrams attempt to show):


(c) 2017
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