Frequently Asked Questions
What is the difference in optics between a front and second surface
mirror?
A front surface mirror differs from a second surface mirror when it
comes to design and the optical quality of images. A front surface
mirror is designed with a reflective layer which is placed directly on
the backing. A second surface mirror has the reflective layer applied to
the backing with a glass or acrylic surface applied over the reflective
layer as a protective measure. The fact that these two types of mirrors
are designed differently has a profound effect on the quality of images
which are produced with each mirror type.
Image quality in a mirror is determined by the reflective process that
takes place with a front surface mirror with a different process
involved with a second surface mirror. Because of the difference in the
design of the two mirrors the image quality is compromised in a second
surface mirror where the quality is preserved with a front surface
mirror and here’s why:
Optics for Second Surface Mirror
The image quality and brightness with a second surface mirror is
significantly compromised as a result of how the second surface mirror
is designed. As mentioned earlier a second surface mirror is designed
with a protective glass or acrylic surface which affects the way the
light reflects on the mirror surface underneath the glass layer. Because
the glass surface layer is present this causes more than one reflection
to occur outside of the primary image. The multiple reflections are
caused by the distance which is created between the mirror surface and
the glass surface when the light is reflected off the mirror surface.
Glass surfaces reflect a certain amount of light and the amount of light
which is reflected can be affected by the temperature of the mirror.
With a second surface mirror the primary image is reflected off the
mirror surface only once before it departs. Because there is a distance
between the glass surface and the mirror surface the reflection from the
mirror surface creates a second ghost image which is displaced from the
primary image. When it reflects off the glass surface and back to the
mirror surface this causes a third ghost image to form.
Depending upon the reflective quality the ghost images can often be seen
which compromises the quality of the primary image. The presence of the
two ghost images occupy a portion of the light intensity which reduces
the intensity of the primary image and compromises the brightness as
well as the quality. The quality is reduced simply because of the glass
surface and the way it reflects light. If the glass surface were not
present the outcome of the image quality would produce a much different
result.
Image Results with First Surface Mirrors
First surface mirrors or front surface mirrors as they are also called
produce higher quality images because they do not have the reflective
issues that second surface mirrors have. This is due to the fact that a
front surface mirror does not have the glass surface applied over the
reflective layer which produces the problems with multiple reflections
and ghost images. Instead a front surface mirror has the reflective
surface applied directly to the backing minus the glass surface. This
allows the image to be reflected at full intensity and brightness which
results in a higher quality image.
If the second surface mirror contains a silver surface which has higher
reflective ability this could potentially produce the same quality
imaging as the front surface mirror. However the fact that the glass
surface is present which will inevitably produce ghost images still
makes the front surface mirror the better option if you require high
quality images. Although a portion of the light is absorbed into the
reflective surface the image quality is preserved since there is no way
for it to reflect off another surface.
Front surface mirrors are used for projects that require superior image
quality without the concern of ghost images and multiple reflections
obstructing the image. So if you require the highest quality image it is
best to go with a front surface mirror for your project and save the
second surface mirror for other purposes.
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