Relevance of Photopic and Scotopic lumens to the Lighting Designers

Time：2016-01-14　Views：2269　Compile：SUNPER

Photopic and scotopic lumens are different and here are details to show this. An example to help one better visualize the difference between the two is as below. Our vision ability is usually different. This is why some people can see far while others cannot. Some can easily see great at night while others may need much light to be able to see different objects at night. Due to these reasons, each one’s perception of light brightness can also be quite different. Glaring light to one person might be normal to someone else. Again, light that might not be enough to someone might be too much to other people.

The above scenario is very important and thus the lighting designers should be aware of it when creating a light installation. Although it is very hard to impress everyone, selecting lamps and lighting fixtures that seem to meet the needs of the majority is probably the best thing to do. The lighting designers start looking for both photopic and scotopic lumens of lamps if things are a bit tricky. To achieve the goal to have lamps and lighting systems with balanced amount of light, there are some things that these manufacturers must pay attention to. They include the following.

Start by knowing what are photopic and scotopic lumens?

To understand these two lumens, it is important to first understand a few things concerning the anatomy of the eye. To start with, there is part of human eye known as retina. This is a part of the eye that responds to light by using unique cells known as photoreceptors and they are found in two types. Rods cells are the most abundant as well as most sensitive to the light. The other is the cones that allow us see color. In dim lighting, we use rods to see. Cones are best at seeing in bright light.

The photopic lumens is a type of light registered by the cones. Photopic lumens are seen in bright light such as light colors and daylight that are clearer. They can be measured using lumen meter or footcandles. On the other hand, the scotopic lumens is what is seen by the rods in the eye. Since rods are used to see in dim light, the scotopic lumens are used for lighting in inside places. Currently, there is no way you can measure them.

Relevance of the above to the lighting designers

Knowing the differences between the two lumens can greatly assist the designers in determining the different sensitivities the eyes may have in different light situations. In addition to this, research has been done and showed that more energy can be saved using fixtures and lamps that focus mostly on scotopic lumens instead of the photopic lumens.

Most of the fixtures and lamps offer an S/P ratio. This is a ratio of scotopic lumens to photopic. The designers use this ratio in figuring out how much light is being produced that can be of great assistance to the human eye. Nowadays, some lighting designers are paying attention to the mesopic light range. Mesopic range is between the scotopic and photopic luemens and occurs when both cones and rods are being used together. If this happens, the viewer gets a better vision in low outdoor lighting locations.

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