1. What is the difference between a fixed
focus and varifocal / zoom lens type cameras?
2. What does the size of a camera's imager
(i.e. 1/3" or 1/4") have to do with lens optics or field
of view?
3. What does PTZ, or pan/ tilt/ zoom equipment
actually do?
4. What is the difference between digital
zoom and optical zoom cameras?
5. Can I obtain panning and tilting ability
without using a zoom camera- or vice versa?
6. Do I need to manually control a zoom lens
type camera- and how?
7. How can I remotely view or control PTZ
camera functions from another location?
8. What is a DC auto iris and why should
it be considered?
Q1: What is the difference
between a fixed focus and a varifocal (or zoom lens) camera?
A1:
Fixed
lens cameras have a set field
of view and cannot be manipulated to produce a wider or narrower
angle. These lenses
are generally found as 3.6mm, 4.3mm, 8mm, 12mm, etc.. The higher
the number of the focal length, the more telephoto the effect,
and the narrower the angle of view. *However- this has nothing
to do with the actual size of the lens itself. You can obtain
a 3.6mm lens which can range in physical size from 1mm (on a micro
pinhole
type camera) to the size of a soda can (for much larger security
type cameras).
Variable focus (or varifocal)
lens cameras allow the user to modify the field of view from its
widest/ most panoramic to the narrowest and most telephoto views
that it is capable of. Some lenses provide a 4-8mm (widest at
4mm and most telephoto at 8mm)- whereas others may provide 5-50mm
for a super zoom in ability.
Many are set up to interface with a variety of optional lenses.
However, there are also cameras with built-in lenses that cannot
be removed or replaced. The removable lens cameras are referred
to as "C"
or "CS" mount because those are the type/ size which
are security industry standards. Many lens choices are available
and the decision should be based on actual requirements for the
application. For instance, if a wide field of view is required,
there may be no reason to include a feature which allows a zoom
to a tighter shot.
It should also be noted that most varifocal cameras are not weatherproof
and will require a suitable enclosure for outdoor use. However,
we do carry these outdoor housings, including those with built-in
heater/ blower. Also, we have an incredible weatherproof integrated
PTZ
camera available (DN-PTZ)
which allows you to facilitate pan,
tilt
and zoom
functions all from a SINGLE control- with all parts protected
inside a weatherproof dome with thermostat controlled heater/
blower inside! Back
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Q2: What does the size
of a camera's imager (i.e. 1/3" or 1/4") have to do
with lens optics or field of view?
A2:
Quite simply, the larger the imager (or image
sensor)- the wider the field
of view a camera will have with the EXACT same lens.
As seen in our 1/3" lens chart- the field of view for one
of our 1/3" image sensor cameras with a 3.6mm lens is 76
degrees horizontal & about 100 degrees diagonal (corner to
corner). When this exact same lens is used with a camera with
a 1/4" image sensor, the resulting horizontal view is knocked
down to only 46 degrees (or a SERIOUS reduction of 30 degrees
horizontal coverage!). Unfortunately, we all too often see cameras
advertised as having 1/3" image sensors- when in reality
they are only 1/4". The sellers don't even seem to make the
time to use a protractor to test if the advertised field of view
is actually deleivered! We only carry a couple different 1/4"
imager cameras for special situations. Please let us know if you
have a need for special order 1/4" units.
NOTE: While there are some higher quality 1/4" image sensors
out there- as well as a ton of poor quality 1/3" and 1/4"
imagers- the GENERAL RULE is that a larger imager will also provide
a sharper image, lower light capability and better color saturation
when compared to an identical camera with a smaller size imager.
ALSO, the size of the camera itself is NOT RELATED to the size
of the imager inside. Back
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Q3: What does PTZ or pan
/ tilt / zoom equipment actually do?
A3:
This can be a big point of confusion as many people tend to group
this type of camera into a single category when there are actually
a wide spectrum of features, abilities, options, and performance
issues to consider. Some are faster than others- some are more
compatible with certain external equipment. Panning is simply
the ability to go from side to side and tilting the ability to
go up and down. PAN
& TILT
are both accomplished by some type of external motor, while the
zoom function (whether manual or remote) is inside the camera
or lens itself. We do carry different cameras that integrate ALL
3 functions (pan, tilt and zoom) into a single control- in both
indoor and outdoor versions.
Weatherproof PTZ
equipment can be rather expensive. Even decent quality pan/ tilt
housings designed for actual outdoor use are very expensive- and
don't even include a the camera or camera housing. We offer a
unique solution to this problem, our DN-PTZ.
It's a special PTZ outdoor spherical dome system with a 220x zoom
(22x optical, 10x digital) with a Sony G5 chip that is the best
we've ever seen- and at a price that is actually affordable to
most security budgets! Please click
here to see it. Please click
here to visit our FAQ answer page about Pan / Tilt / Zoom
equipment. Back
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Q4: What is the difference
between 'digital zoom' and 'optical zoom'?
A4:
Optical zoom is the traditional method of physically manipulating
the disatnce between 2 lenses to create a different camera view.
Digital zooming is a technique in which an electronic processor
literally magnifies size of the pixels imaged by an optical lens.
There are different techniques, but "grainy" appearance
is typically associated with digital zoom, especially when the
camera. Of cameras that have the ability to zoom (aka varifocal
lens cameras), some are optical, some are digital- and some are
both (such as our TV-C270)-
which means that the mechanical lens movement and internal digital
magnification are both taking place (22x optical and 10x digital
= total 220x zoom capability). It should be noted that not all
digital zooming technology is the same. We've seen all ranges
from extremely poor to excellent and are quite pleased with the
equipment we carry. Back
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Q5: Can I pan & tilt
without a zoom camera- or vice versa?
A5:
Absolutely. In fact, many systems referred to as PTZ
are actually the combination of a pan
- tilt
housing with the addition of zoom camera. However, there are also
truly integrated PTZ systems (like our DN-PTZ)
in which the user can choose one or all functions. Back
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Q6: Do I need to manually
control a zoom lens type camera- and how?
A6:
It all depends on the camera. Many variable focal (varifocal)/
"zoom"
lens cameras actually do require the user to set the desired focus
by hand. Others allow it through internal motors to facilitate
remote
control operation. Back
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Q7: How can I remotely
view or control PTZ camera functions from another location?
A7:
Remotely viewing one or many cameras on a distant monitor is not
a huge challenge. However, remotely controlling functions of specialized
camera is where it can get tricky. The problems are generally
the result of incompatible equipment. If the internal software
protocols of the site driver are not recognizable to the camera-
or vice versa- the result will be a functional camera with no
ability to function. This is a strong warning of why it is necessary
to do your homework before designing or purchasing any type of
complex equipment. Again, as with most things- there are a wide
variety of products out there to suit a variety of needs. Please
click
here to visit our FAQ answer page about Pan / Tilt / Zoom
equipment. Back
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Q8: What is a DC auto iris
and why should it be considered?
A8:
A DC
powered "auto
iris" function is basically used to amplify or reduce
light for a lens to obtain a more defined picture view for the
camera. Use of such a camera and lens outfit can dramatically
improve performance in lower lux conditions. You can often spot
such a setup by seeing a cord between the back of the camera body
and the lens itself. It is there to provide a means to deliver
the DC voltage to the ciruitry inside the lens. You cannot simply
attach such a lens
to any camera- even if the mount is a perfect fit. DC auto iris
lenses require voltage and, therefore, a camera with a compatible
DC output. This is why it is recommended that you purchase a lens
and camera together from our company. *We also carry some lenses
with manual iris control. Back
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