Is there some way of finding the optical zoom on a camera, from the mm lens length?

Question

Like if I had an 18-55mm lens, how much would that be in optical zoom?

Answer 1

It's 3x. 55 divided by 18 is just a hair over 3. Simple math.

Answer 2

You mean 55mm divided by 18mm equals 3 making this lens a 3X zoom?



However, a 200mm prime lens that does not zoom (1X for that matter) magnifies a distant object much larger than the 3X 18-55mm lens.



The amount of zoom is just a ratio of how far the lens can change its focal length from its widest angle. In the dSLR world, zoom Xs don't matter. You are more concerned with the mm or focal length. The longer the focal length (higher number), the larger magnification you get.



The other way around, the smaller that number gets, the wider the angle of view, the smaller the subject becomes.



You select and buy lenses according to focal lengths and maximum aperture depending on what you are going to shoot. Different focal lengths serve different purposes and the most extreme at both ends are the least useful in everyday shooting conditions.





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Answer 3

I am guessing that 50 - 55mm would equate to a 1x zoom. So your 18-55mm lens is a wide to normal zoom. Now if you are using a digital camera, you will have to take into account the sensor size. My camera sensor has a factor of 1.6 so 18-55mm becomes 28-88mm for the photograph. Through the view finder it is still a 18-55mm lens.



Here is a way to check - look at an object, and then look at the same object through the view finder. Focus and zoom until the object is the same size in the viewfinder as it is without the camera. See what the mm is on the lens. That is 1x. Then you can multiply by 2, 3, whatever and get the optical zoom for a particular mm.

Answer 4

Simple math. 30 to 90 is 3X zoom. so +/- 20 to 60 =___?

Answer 5

As the others state, divide large number buy small number to get "X" of zoom.



If you are referring to magnification, as in an 8x binocular, that's different. The 18-55 would approximately 0.5-1.5x magnification in those terms.