What is glare – examples of direct glare and indirect glare

I have defined glare in a previous post. In this one I further develop the answer to the question What is glare by listing several examples of glare. Moreover, I suggest which examples of stronger glare might lead to disability glare and classify glare as direct or indirect.  I also explain in which cases glare is particularly deceiving for being too subtle to notice negative effects quickly.

What is glare

Let me repeat the definition of glare for those of you who may not have read the post What is glare and the meaning of glare for a light sensitive person. Glare is a contrast in brightness between different objects in one’s field of vision. Strong contrast in brightness between the objects is equal to strong glare, while a more subtle contrast may be defined as weaker glare. The impact of strong glare is also defined as disability glare. Conversely, more subtle glare may lead to discomfort glare. All these concepts are very well explained in a 2 minutes video What is glare (see below).

What is glare video

What is glare: Examples of stronger glare

Most people (who have normal light sensitivity) might only list these examples if asked the question What is glare. These cases illustrate strong contrast in brightness between different objects in one’s field of vision. The contrast may sometimes reach the level of disability glare.

  • headlights of oncoming traffic – direct glare – and headlights in rear view mirror when driving at night – indirect glare
  • the Sun or bare bulbs with no contrast mitigating object between the source of light and the eyes (shades, sunglasses, fixtures with shades/filters) – direct glare
  • light through the window in bright daylight contrasts with a darker room (no lights on) – direct glare
  • reflection of a lighting fixture on a light-colored surface or a shiny/polished surface in a darker room – indirect glare
  • reflection of sunlight or a light bulb off the darker computer screen such that one cannot see anything that is on the screen in the area that reflects the light – indirect glare
  • reflection of sunshine on water, snow or sand – indirect glare

What is glare: Examples of weaker to moderate glare

Defining examples of moderate glare is tricky, because different people perceive the same brightness contrast differently (depending on their level of light sensitivity). In the post What is glare and the meaning of glare for a light sensitive person I explained the discrepancy between what people with photophobia and people without photophobia might consider strong glare (disability glare) – see the zone named “discrepancy in perception” in the figure below.

What is glare - discrepancy

Therefore, it is important to note, that  if asked a question What is glare? different persons might judge the examples below as glare (people with higher light sensitivity) while others (people with normal light sensitivity) might be surprised that such a case could be considered glare.

Some examples of discomfort glare are:

  • brightly lit part of your work area (desk, kitchen) in an otherwise darker room – indirect glare
  • a brightly lit room next to a darker room (both in the field of vision) – direct glare
  • a bright electronic display device against a dark background and low level general lighting – direct glare
  • ink on paper when reading in sunlight or under a very bright light (a source of glare, you won’t notice it but it can affect you over time) – indirect glare
  • reflection of the sun from a smooth road surface – indirect glare

What is glare that you are not be perceiving as glare?

Finally, a note on the concept of unperceived or unrecognized glare; weak or moderate glare often goes unperceived in the short run. Unfortunately it also has negatively affects (computer vision syndrome – CVS, weariness, lower productivity, headaches). The problem is that the negative effects are only perceived after longer exposure to unperceived glare (for example when you come home from work – you think you are exhausted because of hard work, but it may be that it is because of glare). One way to detect unperceived glare is that when you notice that you have syndromes of glare (computer vision syndrome – CVS, weariness, headache, eye strain), you review your activities of the day and you ask yourself: What is glare that I am not be perceiving as glare? Once you detect it is easier to avoid it. This practice might make your life a lot easier!

Are there any other examples of glare do that you find particularly disturbing or defining of the question What is glare?

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