How to tell the magnification of a lens?

I had just bought a nikon d50 and I'm thinking of getting a telescopic lense. Being a total clown at cameras...as i'm just starting the works.....what does 70 - 300mm mean?? how much X is that?? is it like 3X or 4X?? Please let me know

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Originally Posted by spazticorange

I had just bought a nikon d50 and I'm thinking of getting a telescopic lense. Being a total clown at cameras...as i'm just starting the works.....what does 70 - 300mm mean?? how much X is that?? is it like 3X or 4X?? Please let me know

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In photography we never talk about 3X or 4X magnification and it's a telephoto not a telescopic lens. A lens with a given focal length on a given camera gives a certain view which may be:

"normal" = approximately the same perception as the human eye
"telephoto" = reaches out and just selects a part of the scene compared with a normal lens.
"wideangle" = crams more into the image than a normal view

The kit lens that I assume came with your camera is a zoom so that you can vary the focal length. On your camera with your existing lens:

18mm = moderate wide-angle, useful for buildings & landscapes
28mm = normal, useful for groups and general photography
55mm = moderate telephoto, useful for doing a waist-upwards portrait of a single person sitting 2 metres away

If you add a 70-300mm zoom then you add the following focal lengths and all the others in between:

70mm = telephoto, useful for head and shoulders portait
135mm = long telephoto, tight head shot
200mm and upwards = extreme telephoto, useful for wildlife, sports, etc.

Charles

Welcome to the forum.
The 70-300mm is the focal length of the lens. This found by measuring the distance between the front element of the lens and the film or sensor plane. So at 70mm, the center of the front element of your lens is 70mm from your cameras digital sensor. At 300mm, it is 300mm from the sensor.

The X value you're refering to is found by dividing your focal lenghts by each other. If you take 300mm and divide by 70mm you get about 4.3X. This isn't a "magnification" factor tho. It only means that at 300mm you are shooting at a focal length that is 4.3 times longer than the shortest focal length (70mm) of that lens.

The 3X and 4X that you see is usually refering to cameras with a lens that you can't switched. These cameras can have up to a 10X or even 12X focal range. They might start off with a wide angle such as 28mm and zoom out to 200mm. That would give the camera a zoom range of 10X, but it's still far short of your 300mm lens.

Another example is my 170-500mm lens. This lens has a 2.9X zoom range. That is smaller than your 70-300mm lens, but it has a much longer focal lenght.

Quote:

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Originally Posted by spazticorange

I had just bought a nikon d50 and I'm thinking of getting a telescopic lense. Being a total clown at cameras...as i'm just starting the works.....what does 70 - 300mm mean?? how much X is that?? is it like 3X or 4X?? Please let me know

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For magnification, divide the focal length by 50. So a 100mm lens is a 2X, a 200mm is a 4X and a 300mm is a 6X.

Remember with a Nikon digital camera, the lenses are magnified by 1.5. So that 70-300mm will effectively be a 105-450mm. At the long end, you will get a 9X.

With a fixed lens zoom, the X factor is a ratio of wide to telephoto. And on interchangable lenses, the same principle applies. The 70-300mm is a 4.3X ratio. Meaning, 300mm is 4.3 times as long as 70mm.