If you look through the lens at a distant point, the point image will not move when the lens is rotated slightly about a vertical or horizontal axis the goes through the nodal point. This is called the optical center.
With a thin lens this is close to the geometric center, with a longer complex lens the optical center is buried somewhere inside. The optcial center of a complex lens may or may not be inside an element.
In my experience, generally I known optical center of the lens is the thinnest point of minus lens or the thickest point of plus lens. And in that point (optical center) we can see directly through the lens without any distortion, if the power (dioptry) of lens is correct for your eye. Also we can find it (optical center) by used lensmeter.
outer edge of the lens
It depends on the lens one has on it at the time. The lens is interchangeable.
300m
no it is same
Yes. 5X SCHNEIDER-KREUZNACH VARIOGON Optical Zoom Lens
Optical zoom cameras are used to take a shot in which a far-away object appears both prominently and clearly. Essentially you need a decent zoom lens to obtain this ability, and a good camera with a widely-adjustable lens offers this feature.
That depends on the lens you put on the camera.
axis or optical center
That depends on the lens that is mounted on the Sony A33 DSLR.
Optical Zoom is the true zoom, Digital is basically the zoom in of what the highest optical zoom is. Therefore Optical Zoom is the better zoom, and gives a much clearer picture.
There are two types of zoom, optical and digital. Optical zoom is the actual capability of the lens itself. Digital zoom is what the computer in the camcorder does above and beyond the limit of the lens. If you've ever taken a low-resolution photo and blown it up much larger than the original size, you know what happens. The pixels get bigger, and bigger, and bigger until all you see is a patchwork of squares. That's what digital zoom does, it just enlarges the image that the lens captures, so quality degrades the further you go into the optical zoom range. When you zoom in on an object and the zoom seems to hesitate, or you have to press the button again you know that you are then switching to digital zoom and have maxed out the actual capability of your optical zoom. So, to answer your question, 200x is not always better than 24x zoom, unless of course it's all optical zoom, not digital, which is very rare unless you have a very high-dollar camcorder with inter-changeable lenses.
It is exactly what it sounds like. You zoom in on your subject by using the lens (normally it is attached to the camera itself and can be taken off). You control how far, how much, and where. Usually, optical zoom is used with manual zoom.
ofcourse optical zoom..................