What is the angle of incidence?
The angle of incidence is a term used in physics to describe the predictable nature in which light reflects off a surface. The angle at which a light beam is projected is equal to the angle at which it reflects. These angles are all in relation to a line drawn perpendicular to the reflective surface, which in physics is called the normal. In terms of lighting design, the normal is usually average eye-level at standing height.
How does the angle of incidence affect lighting results?
The angle of incidence comes into play with lighting when the art is located above eye-level, above a fireplace for example.
Have you ever tried taking a picture and found yourself in the reflection? If so, did you move to one side of the other to get out of the picture? You just experienced the angle of reflection. The same hold true for lighting art above eye level – where you position the light and at what angle it shines on the artwork defines the angle of reflection. There is nothing more disappointing than viewing your art, only to see a reflection or glare from of the light source and not the artwork itself. By simply changing the aiming angle of the light you can change the angle of reflection and solve the problem.
Let’s consider an example of a framed mirror hanging over a fireplace (above eye level) and what happens when you view reflections from different positions. Standing straight in front of the fireplace, you can see the ceiling and any light fixtures directly behind you. If you move to the right of the fireplace, you now are viewing the ceiling behind you and to the left. Conversely, if you move to the left of the fireplace, you now are viewing the ceiling behind you and to the right. You now understand the angle of incidence and the angle of reflection.
So, what does all this technical stuff really mean? Well, if you change the aiming angle of the light, you can eliminate reflective glare on the art from one viewing angle or the other but, not both. You have to decide the best viewing angle in the room and mount the light on the opposite side. This will allow you to view the artwork without reflections or glare created by the light source.
Adjusting light on the horizontal plane –
If a projector is placed directly perpendicular to a glossy, glass-framed, or reflective piece of art, the angles of incidence and reflection are both 90 degrees, resulting in a visible glare on the art itself when viewed from center. Where d = distance the projector is offset from the center of the art, as d increases in either direction, so does size of the glare-free viewing zone. If you were to stand outside of this zone and look at the art from the side, you would see the glare.
Testing angle of incidence –
The best way for an individual to test this theory and to understand the phenomena firsthand is to perform a test using a flashlight. You will need a suitable step ladder, a flashlight with an adjustable beam, a tape measure and an assistant. Measure the distance down from the ceiling to the top of the art plus 1/3 of the art height to approximate the distance out from the wall for the light to achieve the 30-degree angle.
Start by asking your assistant to climb the ladder and hold the flashlight at the ceiling pointing towards the art from the recommended 30-degree aiming angle calculated above. Move around the room and view the art from all angles from both standing and sitting positions. Next, move the light in various positions left and right to find the best position to address any reflections or glare. The goal is to expand the glare free viewing area and shift any reflections to lesser viewed areas of the room.
Locating your projector in the ceiling –
At Phantom, we use a fairly simple mathematical formula to determine the optimal placement of the projector in the ceiling: C + 1/3 of art height + 4 = D where C = distance down from ceiling to top of the art and D = distance out from wall where the projector should be mounted.
Homeowners invest thousands of dollars into their paintings and sculptures, and hundreds into fixtures to display them. In short, it’s a big deal that the display look as sophisticated as possible. Even the smallest mistake can make the fixtures look off or sloppily arranged. For a homeowner that takes pride in their collection, poor illumination can be a nightmare.
Proper art light placement takes real planning, as it’s not just about filling the space with illumination. Unlike standard fixtures, which are used to brighten up an entire room, display fixtures are aimed precisely at a subject and have to be shaped to maximize the effect. This means accounting for things like glare and shadows, and setting up the fixture so that it produces the optimal beam angle. An illumination expert can help overcome these obstacles and prevent the frustrating trial and error that often comes with setting up fixtures.
One of the major advantages of Phantom Lighting projectors over other light sources is the ability for offset mounting to address reflective glare. Our variable optics system allows for short wide and long throw offset mounting positions without spill light on the wall around the art. Controlling the shadows around the artwork is just important as lighting the artwork itself. Visually, we are accustomed to seeing shadows below the art when using recessed lights. Shadows cannot be completely eliminated when working with light, but by offsetting the beam, you shift those distracting shadows to the opposite side, which is a less distracting result.
Does non-glare/antireflective glass really work?
If you’re looking to display works of art in your home or business, you might be curious about the efficacy of non-glare framing glass versus standard glass. Does non-glare glass really eliminate glare? Yes, non-glare and anti-reflective surfaces can assist in the removal of reflections and hot spots. High-end custom framing shops and art galleries usually offer both a non-glare glass and an anti-reflection glass. The difference between the two, besides the cost, is that non-glare glass is etched, while anti-reflection glass is coated with a special material. However, there are some disadvantages to non-glare or anti-reflective framing glass that you might not have considered:
It is important to remember that while some artworks can be dulled by non-traditional framing glass, other artworks may be unaffected or even enhanced. The disadvantages don’t necessarily mean that anti-reflective or non-glare surfaces aren’t the right way to go. They can and do offer a variety of benefits as well, including:
How can a professional help with eliminating the glare from art that comes with glass?
Any subject that has a tendency to reflect light has to be illuminated with high-quality, flexible fixtures. It’s impossible to remove reflections if the fixture can only be installed directly in front of the subject. All this will accomplish is throwing light right back into an observer’s face. Instead, the fixtures have to be arranged with the specific intention of mitigating reflections, and this takes some careful positioning.
Lighting reflective surfaces is an extra challenge when putting together a display, as the intensity of the light, along with its position, can affect how the surface throws reflections. For example, optical framing projectors are normally the choice when lighting creative subjects, and they can work with reflective subjects as well, but they are harder to position just right. Some lighting experts will instead opt for a diffused light, either placed directly above the subject or below it. Such a light could be installed inside a pedestal, for example. A diffused fixture creates an even level of light instead of a single, intense beam, and this prevents reflections. However, it may not create the dramatic look that a homeowner is aiming for.
If a lighting expert uses an optical framing projector with the subject, they will then have to use positioning to ensure they are eliminating glare from art with glass. Projectors are typically installed inside the ceiling for concealment, and they often come with components that make fine aiming a possibility. For example, Phantom’s projectors are built with a rotating ring and a mounting cradle that, together, allow for 360 degree horizontal aiming, and vertical aiming up to 55 degrees.
Again, the projector should not be installed directly in front of the subject, as the angle at which the beam hits the subject is equal to the angle it creates as it reflects off. The better option, then, is to offset the projector so that it bounces the reflection away from any standard viewing angle. This process can take some trial and error, though, as some glass sculptures can scatter the light and cause multiple reflections with a single beam. An experienced lighting expert, though, has worked with various reflective subjects and can quickly assess how the subject is interacting with the projector.
How can art hanging over a sofa be properly illuminated without blinding anyone who sits there?
One of the best ways to control spill light on the sofa is by using a light fixture that has a focused light source. Optical framing projectors, like the Phantom Contour Projector, produce a high intensity beam of light that can be shaped to fit the contour of the object. This technique eliminates all the light around the art on the wall and the sofa below. If spilled light isn’t an issue for you, you could also install a MR16 low voltage adjustable halogen accent light mounted above the sofa and out of the field of view. From a steep aiming angle there will be some light on the wall around the art without bothering anyone sitting on the sofa.
Avoiding Shadows Caused by Deep or Ornate Frames
Many antique traditional artworks are housed in very deep or ornate frames that can sometimes create an unsightly shadows when illuminated with an optical framing projector. There are two shadows that might occur with a deep frame – one on the top of the painting itself and another on the wall at the bottom of the painting, both created by the depth of the frame. One way to avoid both of these shadows is to contour the light to the canvas itself, instead of the canvas and the frame. Achieving the correct aiming angle can also help avoid shadows. If your artwork has a deep or ornate frame, it’s best to consult with a lighting expert before getting started to ensure the optimal results.
If you still have any questions about how to avoid shadows and glare or why Phantom Projectors are the best choice on the market, give us a call toll-free at 800-863-1184 or request a quote using our online form. The lighting experts at Phantom are ready to talk to you about the best design plan for your project!