Variable focal vs zoom
- Thread starter freqflyer
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ThePeacockRanch
Young grasshopper
Zoom operates remotely from software. Variable means you are on the ladder moving a lever on the camera lens itself.
fenderman
Staff member
- Mar 9, 2014
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Varifocal can be manual or motorized. Generally speaking, zoom is a term reserved for Pan tilt Zoom cameras. Motorized varifocal is often slow because its not intended to be used in real time for zoom functions. True ptz cameras have a much faster zoom function.
fenderman
Staff member
- Mar 9, 2014
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Zoom changes magnification or perceived distance to object. Then the system focuses. You can zoom in on an object and have a blurry image. (With auto focus off).
In Variable focal ( typically needed for larger aperture), the lens is fixed magnification or view angle but you can view a near object or far object and adjust both to be in focus. Buy comparison, many cameras have fix lens ( small aperture ) where everything is in focus..beyond some minimum distance.
In Variable focal ( typically needed for larger aperture), the lens is fixed magnification or view angle but you can view a near object or far object and adjust both to be in focus. Buy comparison, many cameras have fix lens ( small aperture ) where everything is in focus..beyond some minimum distance.
nayr
IPCT Contributor
Zoom only means the range from the widest to the narrowest.
5mm-50mm = 10x Zoom
50mm-500mm = 10x Zoom
obviously both are not equal magnification; by its self, the level of Zoom is a meaningless marketing term..
If you didnt know any better you could buy a 2mm-60mm listed as a 30x zoom, not realizing that it wont see any farther than a cheaper 6-60mm 10x zoom lens.. only closer and that seems counterintuitive.
5mm-50mm = 10x Zoom
50mm-500mm = 10x Zoom
obviously both are not equal magnification; by its self, the level of Zoom is a meaningless marketing term..
If you didnt know any better you could buy a 2mm-60mm listed as a 30x zoom, not realizing that it wont see any farther than a cheaper 6-60mm 10x zoom lens.. only closer and that seems counterintuitive.
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CamFan
Getting the hang of it
Generally there are 2 types of zoom lenses.
Parfocal - lens says in focus while zooming in & out
Varifocal - lens needs to be refocused while zooming in & out.
Parfocal is way more expensive. The 2 ways to achieve a parfocal that I know of.
1. Mechanically using cams inside the lens barrel to move focus element(s) while zooming
2. Software - using motors, you can adjust focus as a function of zoom to stay in focus. Sony's SCL Zooms are parfocal, electronically (not autofocus).
Most, if not all security cameras (& dslrs) are varifocal. Generally you use huge depth of focus or autofocus on these cameras.
I've only seen (mechanical) parafocal lenses in the $10K - $200K pricerange, for cinema/TV use.
Parfocal - lens says in focus while zooming in & out
Varifocal - lens needs to be refocused while zooming in & out.
Parfocal is way more expensive. The 2 ways to achieve a parfocal that I know of.
1. Mechanically using cams inside the lens barrel to move focus element(s) while zooming
2. Software - using motors, you can adjust focus as a function of zoom to stay in focus. Sony's SCL Zooms are parfocal, electronically (not autofocus).
Most, if not all security cameras (& dslrs) are varifocal. Generally you use huge depth of focus or autofocus on these cameras.
I've only seen (mechanical) parafocal lenses in the $10K - $200K pricerange, for cinema/TV use.
Kawboy12R
Known around here
- Nov 18, 2014
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"Zoom" is the ratio of maximum to minimum lens length on a varifocal lens. The term by itself describes nothing about how the lens length adjustment is achieved. However, virtually all PTZ cameras have remote controlled motorized lens length adjustment ("zoom") with automatic refocus. If you buy a fixed varifocal cam (by fixed I mean no motorized pan or tilt), then you'll have to read carefully to see if it has motorized remote lens length and focus changes or if you have to fiddle with screws in the camera to manually adjust lens length and focus while up a ladder and holding a laptop in your teeth. With most cams you'll probably only ever do this once and then leave it but it's awfully nice to have. I generally use a smartphone but it can be hard to get the focus just right with such a small screen, particularly if it's sunny.
I'm with you Kawboy12R. I don't mind it being a pain once since that's the only time I'm going to mess with it.