Can someone explain the lenses to me please

Could someone please explain all about all the numbers on the lenses? What is the difference between 18-55mm & 17-85mm (I think I wrote that right) What do all these numbers mean?

Thanks
Candice

These are the focal lengths that the zoom lens will cover. A zoom lens covers a range of focal lengths and a prime lens is only one focal length. One covers from 18mm thru 55mm, and the other 17mm thru 85mm so obviously the second one has more of a range.

That's not necessarily an advantage becuase there could be tradeoffs with that. Used to be that the longer the zoom range, the less sharp a lens would be at the ends of the range but newer lenses have gotten a lot better.

Almost as important as the focal length range is the aperture range, or f-stop. The number listed will be the maximum f-stop, or as wide as it will go (i.e. f3.5, f5.6, etc). A lot of zooms will have a variable aperture so that they're a little faster (lower number) at the wide angle end of the range but one or two stops slower at the telephoto end of the range.

The focal length of a lens determines whether a wide angle portion of the scene is captured (small numbers) or a narrow section (high numbers. Here is a page that shows the same scene captured with many different focal lenths from 40 to 600 on a medium format film camera.
http://www.luminous-landscape.com/tu..._lengths.shtml
When you see 2 numbers with a hyphen between, the lens is a zoom lens with those focal lengths as a maximum and minimum.
The angle of a scene captured also depends on the size of the film or digital sensor since a smaller area will capture a smaller angle of the scene - all other things being equal - so a 35 mm lens may be a wide angle lens on a 35mm film camera but a normal or even telephoto on a digital camera.

Thank you that helped a lot!

Can you explain one more thing for me, how do THESE filters work where they are all in different sizes? How do you know what size to buy?

Thanks
Candice

Quote:

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Originally Posted by Candice

Thank you that helped a lot!

Can you explain one more thing for me, how do THESE filters work where they are all in different sizes? How do you know what size to buy?

Thanks
Candice

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The size of the filter you need depends on the size of the threads at the end of the lens. At the business end of the lens, there will usually be a size marking that's sort of a circle with a line through it, followed by a number like "67mm". That's the filter size you need for that particular lens. In order to avoid buying different filters for all of your different sized lenses, you can buy step-up and step-down adapter rings that will allow you to fit a 67mm filter on a 62mm threaded lens, for example.

As far as the filter you linked to, that's a color correcting filter, which digital has basically rendered obsolete. Instead of adding a filter in order to balance daylight film for indoor use, for example, with digital you just change the white balance from daylight to flourescent or incandescent.

The main filters you should consider are circular polarizers, which cut reflections and increase color saturation...neutral density filters, which cut the amount of light going into the lens to allow for slower shutter speeds....and graduated neutral density filters, which allow you to expose for the darker portions of a seen without blowing out the brighter portions.

Some people might recommend a UV filter for protection, but IMHO, they are unnecessary.

Hope that helps...