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- Image Format: 1/3"
- Mount: CS
- Focal Length: 3.5-8mm
- Aperture: F1.4
- Angle of View: 95.3-44.3
- Operation: Manual
- Size: 32 x 50mm/1.26 x 1.97in
- Made of quality material
What Is a Varifocal Lens?
In Animal Vision
- The lenses in humans' and other animals' eyes flex to shift sharp focus between distances. Bi- and trifocal corrective lenses are properly multifocal, rather than varifocal, meaning the viewer, rather than the lens, does the shifting. Early in 2010, however, the U.S. Food and Drug Administration approved the first "accommodating" lens for implantation after cataract surgery, flexed by eye muscles like a natural varifocal lens
- The optical zoom lens on almost every digital camera is varifocal, though it's actually a system of lenses that changes the distance between its components. The long zoom lens that snaps onto an SLR (single-lens reflex) camera, digital or not, is the classic form
In Surveillance Cameras
- Variable focus in a single lens came to security cameras in the 21st century, but is usually set manually: When you set up your surveillance system, you can choose where in its field of view you want each camera to focus. The camera doesn't zoom in on suspicious activity, and you can't refocus recorded video to read a license plate
- 1 x Zoom Lens
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• If the order has not been shipped; please contact DinoDirect Live Support for order cancellation.You will get your refund within 24 hours.
• If the order has already been shipped; you may return the item to us postmarked within 30 calendar days of delivery. Please contact our Live Support to inform that.
• Please contact Live Chat or click here to learn more return policy.
- What are the advantages and disadvantages to having a zoom camera lens with a fixed f stop?
I'm not totally sure what you mean by "fixed f-stop," but I will assume that you mean a "constant aperture" zoom. Such a lens would be specified as the Canon Zoom Super Wide Angle EF-S 17-55mm f/2.8 IS USM Autofocus Lens ($1,000), rather than the Canon Zoom Super Wide Angle EF-S 17-85mm f/4-5.6 IS USM Autofocus Lens ($500).
The main advantage is that you do not "lose light" as you zoom out. With the cheaper lens above, you see that the maximum aperture at full zoom is f/5.6. This is the reason why point and shoot cameras have such terrible flash range as you zoom in closer, but you don't need to worry about that so much with your Rebel XT. You can get nicer depth-of-field effects if you don't automatically stop down just by zooming.
The disadvantage is that the glass is bigger, so the lens costs more money - lots of it - and the lens is heavier. You will also have to buy larger diameter filters, which cost more money.
- Does every camera zoom lens changes its aperture when changing the focal length?
No. Generally pro or prosumer lenses have fixed aperture all through the zoom range. Standard lenses entry level lenses as well as most kit lenses have variable aperture.
- How far is the most a television camera lens can zoom?
It's hard to tell without knowing the exact lens focal lengths. 300x tells me it will have a big zoom, but depending on what sort of lens it has, this could vary greatly.
Also, this totally depends on the field of view you're looking for. If you want to zoom in on someone's face, then they will have to be closer than if you wanted to zoom in on, say, a car.