What does the window on SLR lenses with the infinity sign do?

Question

On camera lenses like:
http://www.amazon.com/gp/product/B000G25NHC/ref=noref/105-4801697-9231638?ie=UTF8&s=electronics

Answer 1

It shows the distance at which the lens is focused. With infinity showing, your lens is focused for infinity. If it shows 3, it is set for 3 meters or feet depending on which scale you use - you can see the ft/m scale to the right of the window,

Sorry Steven J, but the window does not show depth of field, at least not directly. Depth of field is related to both the focal length and the f stop. On this lens you can find the depth of field by looking at the f stop numbers shown below the window. On this lens - if your f stop were 4 and you were to rotate the lens so the infinity symbol was dierctly opposite the #4 on the right, your depth of field would be from about 3 meters to infinity.

Answer 2

On all SLR lenses, they have written the measurement of focusing distance.That means if we focus an object 3 meters from the camera and it is in focus, we will see, it will be at the point of the number 3 on the SLR lens.Such as after a particular distance everything will be in focus beyond the skylimit.Then we will see the infinite mark come around at the center of the SLR lens.Means if you see the moon or star in focus with the camera, the lens distance indicator shows it is "infinity".

Answer 3

The window in which the infinity sign appears sets the depth of field. When set at infinity, everything at all distances will be in focus. When set at a smaller number, everything up to the distance set will be in focus and everything further away will be out of focus.

Answer 4

The number UNDER the distance scale show depth of field. "How quaint" to find a digital lens that still actually does this! I guess it's because Sony is just using old parts from Konica/Minolta...

Answer 5

it allows you to focus on any distant object