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Be sure to check out our Lens Calculator .
EXPLANATION OF THE FOCAL LENGTH OF A LENS
What does the "mm" value mean
to me?
1.8mm
to 2.3mm - SUPER WIDE ANGLE:
This focal length is only used when you need to see a lot of area - I
mean a lot! Before you say "that's what I want", keep in mind
that the more area you see, everything in the picture is smaller on the
screen and may take on a fisheye or curved look. Super wide lenses are
typically more expensive.
2.7mm to 3mm - WIDE ANGLE: Good for most
applications and will work well inside or where your subject is close
to the camera. These lenses have an "angle of view" between
90 and 100 degrees. Place a camera with this focal length in the corner
of a room and you will see the whole room except for the area directly
below the camera.
3.5mm to 6mm - NORMAL ANGLE: Good for most
applications except for small rooms, close up subjects, and wide coverage
areas. Angle of view is between 50 and 80 degrees.
8mm to 100mm - TELEPHOTO NARROW ANGLE: Good
for longer distance applications. Need to see the gate at the end of the
driveway or the rollup door across the warehouse? This is the lens range
you will most likely need. The Angle of view is between 37 and 3 degrees.
Need
a recommendation? This is our favorite lens
that works great for about 95% of all applications (the Fujinon YV2.8x2.8LA-SA2L).
Need to
see that gate from 800' away? No problem - give us a call. We have lenses
that will allow you to see subjects from a great distance.
EXPLANATION OF LENS APERTURE - What does the "f/#"
mean to me?
Simple -
the lower the "f" number, the more glass the lens has. More
glass allows more light to reach the CCD sensor in the camera allowing
it to perfom better in lower light conditions. So a f/1.0 lens will "see"
better in low light than a f/1.4 lens etc.. Have plenty of light in your
scene 24/7? Then don't worry about the aperture number.
EXPLANATION OF AN "IR" CORRECTED LENS:
Most types
of artificial lighting emit some level of invisible infrared light. When
the scene is bright, this is not a problem because the automatic iris
inside the lens closes down and consequently, the image's range of sharpness
increases. At lower lighting levels however, this infrared light will
shift the focus range of the lens and will cause a picture to look a little
fuzzy. An IR corrected lens compensates for this phenomenon and produces
a sharp image under all types/levels of lighting.
EXPLANATION OF AN ASPHERICAL LENS:
A regular
lens utilizes glass elements that are perfectly round throughout the entire
surface of the lens. The picture area of a camera, however, is rectangular
so the corners of a picture can sometimes be not as sharp as the center
of the image. An aspherical lens is made using a special process that
essentially flattens out the glass in certain spots to allow a picture
that is just as sharp in the corners as it is in the middle. It can also
help brighten the image in the corners as well. The special glass is slightly
more expensive but well worth it if you seek the sharpest possible images.
Be sure to check out our Lens Calculator .
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