Magnifying Mirror Information
How do magnifying mirrors work – the easy stuff?
1) The simple explanation is that because the curvature of the mirror reflects light at an angle the reflected image is magnified.
2) The complex explanation is that there is a lot of physics and math behind the magnification.
Let’s look at some simple points first.
1) The amount of magnification is determined by two factors;
a. The curvature of the glass – for any given mirror this is a fixed number and doesn’t change.
b. The distance of the user from the mirror, which, of course, is variable.
Skipping the details for the moment – up to a point, the further away the user gets from the mirror the larger the image.
2) Magnifying mirrors are rated for their power of magnification based on how much bigger they make an object look. A plain flat mirror would be rated at 1X and one that makes an object 3 times larger would be rated at 3X. For make‐up and shaving mirrors the most common ratings are 3X, 5X, 7X and 10X. There is a formula for the magnification but, unfortunately, it is not always applied correctly.
3) For most users a 3X or a 5X mirror works very well. Perhaps if the user’s vision is declining a bit or if they are doing very detailed work a 7X mirror would be appropriate. In a pocket size compact or other small diameter mirror a 10X magnifier works but in a larger mirror the image becomes less useful as you look further away from the center of the reflection.
4) A poorer quality mirror may show some distortion or waviness that will affect its usefulness.
5) Because its surface is harder and not as easily damaged a glass mirror will provide longer life than a plastic mirror and most metal mirrors.
6) Any mirror should be cleaned carefully. For glass mirrors use a soft, damp cloth and, if necessary a little mild detergent or glass cleaner (like Windex). Never use abrasives or scouring pads. Remember that some of the finishes on other parts of the mirror are not as damage resistant as glass and treat them accordingly. For plastic or other mirror materials refer to the manufacturer’s directions.
The simple summary is that a 3X or 5X mirror should work well for most people. When choosing a mirror, check the quality of the reflection and then decide if the magnification meets your needs. Once you have a mirror follow the manufacturer’s instructions for cleaning and maintaining it.
How do magnifying mirrors work – the technical stuff?
1) Mirrors function according to the laws of physics – in this case the laws of reflection.
2) Ray diagrams are a useful way to help understand how these laws work in magnifying mirrors. Basically they track the path of two light rays as they pass through specific points and are reflected from the face of the mirror. In the following diagram we are concerned with 3 points, the center of curvature, the focal point and the top of an object. Our two light rays behave as follows:
a. Ray 1 originates at the center of curvature, passes through the top of the object and is reflected back through the center of curvature – but we perceive it as passing on through the glass in a straight line.
b. Ray 2 originates at the focal point, passes through the top of the object and is reflected back parallel to the axis of curvature – but we perceive it as passing through the glass in line with this reflection.
c. The two lines intersect at a point behind the mirror which is the top of the image. The bottom of the image is a point on the axis directly below the top of the image. Because it’s on the back side of the mirror where you can’t actually see it it’s called a virtual image
3) So let’s look at a ray diagram. First let’s define some of the variables
a. R is the radius of the curved surface of the glass
b. F is the focal distance of the mirror – it is 1/2 of the radius of curvature
c. H0 is the height of the object we’re reflecting
d. D0 is the distance of the object from the center of the mirror
e. H1 is the height of its reflection
f. D1 is the distance of the reflection from the face of the mirror
g. M is the magnification of the mirror
h. R, F, H0 D0 are either known or can be fairly easily measured
i. H1 and D1 need to be calculated and once we know them there’s a simple equation for M
Next let’s look at the equations for this mirror.
j. The mirror equation
k. The magnification equation
2) Using some high school algebra you can arrive at the data for this table (dimensions are in millimeters and numbers have been rounded)
Lighting in BACI Mirrors.
Our most popular Baci mirrors use LED light sources but some models are still available with incandescent lighting for those who need to match the look in an existing installation or are not yet ready for the newest technology. Our LED mirrors offer the following advantages:
High light output • Natural white light • Accurate color rendering
Energy efficiency • Long life • Operate on universal voltage
Light Output.
The amount of light from a light source is usually measured in Lumens. A simplified technical definition of a lumen is the total amount of visible light emitted by a source. To offer a familiar reference point, a typical 25 watt incandescent light bulb emits about 230 lumens.
Light sources in Baci mirrors emit the following amounts of light: 775 Lumens
Natural White Light.
LED’s and other light sources can produce light in a wide range of colors, however, for make-up mirrors we’re primarily interested in white light. But, as you’ve probably discovered, there are many colors of “white light” ranging from the soft warm glow of a candle to the bright blue/white of some automotive headlamps.
The color, or hue, of light is referred to as its Correlated Color Temperature (CCT) and is usually measured in degrees Kelvin. In technical terms CCT is roughly the color of a block of carbon heated to a specific temperature on the absolute (Kelvin) scale. For example, the color temperatures of some common light sources are:
40 watt incandescent lamp • 2500º K
Cool white fluorescent lamp • 4200º K
Noon daylight • 5500º K
Light from Baci mirrors are targeted at the following color temperatures:
High power LED • 3500º K
Medium power LED • 4000º K
Low power LED • 5000º K
Most colors of light can be produced by mixing various amounts of Red, Blue and Green light as seen in the charts below. The chart on the left shows that combining red, green and blue light produces white light. Variations in the intensity of each component produce the many different shades of white that we see. The chart on the right shows a range of colors produced when various proportions of red, green and blue light are mixed. Note that white light is only seen in a small area near the middle of the chart.
Accurate Color Rendering.
The CCT describes the color of light emitted by a light source. But we also have to look at another number to consider how that light makes things look. That number is the Color Rendering Index or CRI. It is an indication of how natural things look under light from a specific light source compared to how they look under daylight.
Overall, light is made up of a spectrum of wavelengths and intensities and different light sources contain different spectrums. That can be true even when the color (CCT) of the lights appears to be the same. We perceive objects based on the spectrum they reflect to our eyes. So when an object is illuminated by sources with different spectrums it will look somewhat different under illumination from each source.
CRI is a means to evaluate these differences. CRI is computed from a measurement of how several specific color samples look under light from the source being tested compared to how they look under light from a reference source with the same color temperature. If you compare the CRI’s of two light sources with the same CCT the one with a higher CRI will render colors more naturally.
But remember that the CRI is only meaningful when you’re comparing light sources of the same CCT. For example both an incandescent lamp and natural sunlight have a CRI of about 100. But the incandescent lamp has a CCT of about 2500° K vs. the 5000-6000° K of the sunlight and an object seen under the incandescent illumination will look yellower than one seen in sunlight.
Typical high power LED’s in the 3000° K to 4500° K range have CRI’s of 70 to 80. Baci medium and high power LED mirrors have a minimum CRI of 80 which is one of the highest available in comparable light sources. The IES Bathroom Lighting Guide recommends a CRI of 80 or better for applying make-up.
Energy Efficiency.
LED’s (Light Emitting Diodes) produce visible light by passing relatively low power electrical current through a semiconductor. Based on the chemistry and technology the LED emits visible light and some heat. Incandescent lamps produce visible light by passing higher power electrical current through a filament. The filament gets hot enough that it produces visible light and also quite a bit of heat. LED’s are far more efficient than incandescent or even most fluorescent lamps, producing more light and less heat while consuming less energy.
Efficiency in Baci and Echo mirrors is as follows:
High power LED • 775 Lumens • 6 Watts • 129 lumens per watt
Medium power LED • 465Lumens • 3 Watts • 155 lumens per watt
Low power LED • 260 Lumens • 4 Watts • 65 lumens per watt
Incandescent • 120 Lumens • 15 Watts • 8 lumens per watt
Long Life.
LED’s tend to have very long lives in comparison to incandescent lamps. High power LED’s have an average life of as much as 50,000 to 100,000 hours where incandescent lamps have an average life of about 1000 hours. In either case consider that a make-up mirror is typically used for less than 30 minutes per day and that translates to about 5 years for an incandescent light source and 100 years or more for a LED light source.
Universal Voltage.
Baci LED mirrors are designed to operate on virtually all international electrical supplies. In other words, they’ll work in countries like the US where the standard current is 120 Volts at 60 Hertz, or in countries like Germany where the standard current is 240 Volts at 50 Hertz or even in Japan where the current is 100 Volts and can be at either 50 Hertz or 60 Hertz.
Baci LED mirrors include an electrical device that converts the input power to the characteristics that the LED’s need. These devices are not suitable for use on dimmers or some power management systems that alter the normal supply parameters. If you need to operate on one of these systems please contact us.
Incandescent mirrors are typically supplied for operation on 120 volt.
Baci mirrors furnished with a cord and plug are typically supplied with US style plugs but can be supplied with plugs for most other countries on special order.
A brief guide to the things you should consider when selecting a personal grooming mirror.
The first things to consider when choosing a make-up or shaving mirror include:
1) Will it be mounted on the wall or be on the countertop?
2) Will it be lighted?
3) How much magnification?
Then you need to consider:
4) If it’s wall mounted, will it be straight ahead of you or at your side?
5) If it’s on the countertop, will you be sitting or standing up?
6) If it’s lighted, how much light and which kind of lighting do you want?
7) Do you need a mirror with a magnifier on one side and a plain mirror on the other?
After answering these questions, the next step is to look at the various mirrors that are available and consider these six important features that will help you choose the one that’s right for you.
Style
• Is the overall style compatible with the rest of your decor?
• Does the finish match your plumbing fixtures or otherwise blend with the other fittings in the room?
Quality
• Is the overall construction sturdy?
• What is the mirror made of – brass is considered preferable in damp areas like a bathroom but steel is also acceptable if the finish is high quality and corrosion resistant. Some plastic is also satisfactory for frames and other non-moving parts.
• Other than obvious scratches and similar flaws it is hard to tell the quality of the finishes – until they fail. The best indicator of finish quality is the reputation on of the manufacturer.
• Is there a warrantee and, if so, read it to see what’s covered and for how long.
Reflection
• Most users will find a 3X mirror acceptable and a 5X mirror a little better. If your eyesight is poor a 7X mirror may be advisable. While a 10X or higher mirror is okay in a small diameter compact or hand mirror as the diameter gets beyond about 6” you will begin to see some distortion around the outer parts of the reflection.
• No matter what the magnification, check your reflection to see if there is any waviness or other distortion.
Lighting
• Most bathroom lighting is inadequate for close work like applying make-up or shaving. So the choice of lighting is probably your most important decision when selecting a make-up or shaving mirror. The two essential qualities to consider are the type of lighting and the amount of light. There are generally three kinds of lighting – incandescent, fluorescent or LED. Each has its own features, advantages and disadvantages.
A) Incandescent lighting comes from the familiar Edison style light bulb. Typically in make-up and shaving mirrors they range from 15 watts to 40 watts. The color of the light is soft and warm but they also generate a fair amount of heat. Lamp life is shorter than either fluorescent or LED lighting so you will have to replace the lamps more often.
B) Fluorescent lighting comes from smaller versions of the fluorescent lamps you see in commercial areas and some more modern shapes that that are seen in Compact Fluorescent Lamps. These lamps are available in a range of colors but the light tends to be bluer than incandescent lamps. However, they produce more light and less heat, use less energy and last longer than incandescent lamps.
C) LED lighting is the newest and most technological light source. Depending on the electronics, chemistry and manufacturing processes colors can be virtually anywhere in the visible spectrum and brightness can run from barely visible to blindingly bright. Energy use will be much less than incandescent or fluorescent lamps and lamp life will be significantly longer. So the utility and quality of LED lighting in a make-up and shaving mirror depends on the manufacturer’s choices of what to build into the product. You can get some information from the technical specifications for color (CCT), light output (Lumens) and Quality of light (CRI) but the best way to judge whether the particular color and output are right for you is to actually look at yourself in the mirror.
Electrical Supply
• Almost all incandescent and fluorescent mirrors are built to operate on the power supply in the country where they’re sold – in the US and neighboring countries 120 Volts at 60 Hertz, in Europe and much of the rest of the world 250 volts at 50 Hertz. So you should only need to verify that the mirror was built for your market.
• Many but not all LED mirrors are built to operate on universal voltage – thus anywhere in the world. So again, only a quick check of the specifications is all that should be necessary.
• What’s more important is whether the mirror will connect to your power supply without problems. For a wall mirror, will it mount on your outlet box properly? Will the wall plate fit the available space? And will it cover the outlet box opening in the wall? For a portable mirror, will the plug fit into the wall outlet properly?
• Most mirrors have a self-contained on/off switch but check to be sure that you will not need to add a switch to your electrical system.
• Even the highest wattage incandescent mirrors do not have large power requirements so your existing electrical lighting circuit should have enough open capacity to handle a mirror. However, mirrors with a convenience outlet should only be installed on a circuit rated for power outlets which has a grounding conductor and preferably a Ground Fault Current Interrupter.
Cost
• Mirrors run the gamut of prices from very low to astonishingly high. In general the old saying “you get what you pay for” applies; especially as regards quality, performance, durability and satisfaction. Most of us wouldn’t mind owning a Rolls Royce but few of us need or can afford one so we choose the car that best fits our needs and budget. Similarly the proper choice for a mirror is to select the one that meets your needs and is within your budget.
• A lesser mirror may be fine for a few years but then it has to be replaced, while a top of the line mirror can provide a lifetime of service.
• Remember also that you are buying this mirror for the specific purpose of applying make-up or shaving. Choose one that allows you to accomplish that in comfort, with the right power of magnification, the right amount and quality of light and a clear, undistorted reflection.
• On top of that, you will want a mirror that is attractive, trouble-free, low maintenance and energy efficient.
You might also want to consider how many mirrors you need. Even if you don’t install them now you might want to consider provisions for adding them later.
• Many modern bathrooms have a wide vanity with dual sinks – one for her and one for him. Adding a grooming mirror at each sink is a nice feature that adds convenience and efficiency for both of you.
• A make-up mirror in the guest bathroom will be appreciated and will make your guests feel valued and pampered.
• A good make-up and shaving mirror in every bathroom will add to the value of your home. Besides the kitchen, the bathrooms are one of the most considered features when buying a home.