OK a few more questions. Are the lenses that I can purchase seperately going to fit either a Nikon or Canon, or do they have their own lenses. Also if I decide to upgrade to a better body later on will the lenses interchange between models of the same brand. I am leaning towards the Nikon D40 or D60 at the moment. Are there any good forums about these cameras that you guys are members of?
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Those are two of the biggest I'm aware of.
I can't speak for Nikon. Canon lenses may or may not be interchangeable - depending on what you buy. Lenses designed for APS-C or APS-H sensor sizes will not produce acceptable results if someday you decide to make the move into full frame sensors (currently the 5dmkII is the entry level full frame from Canon at ~$2700). On the other hand, lenses capable of producing acceptable images on Canon's full frame models will interchange and perform well with either APS-C or APS-H sensor models (we call them "crop" frame cameras for short).
Nikon is relatively new to the full frame sensor level. Nikon shooters here can advise whether there is a seperate line of lenses for the 700d.
If price is an issue, good lenses are usually a better investment than a more expensive camera body. Never skimp on glass to get the latest whiz-bang feature on a camera.
When you look to purchase lenses, don't fixate only on the focal length (the mm number). That's only part of what the lense does. The second number, the "f-number" is also important.
Focal length breaks down kind of like this for a crop frame camera:
10-17mm extra wide angle, with "fish-eye" effect at the widest end. Be careful taking photos in this focal length range, as it's easy to get your toes in the shot.
18-35mm wide angle...good for landscape shots.
35-50mm...pretty normal, undistorted view similar to what one's eyes see.
50mm-70mm...pretty good range for headshots and up close portrait work. Tends to not "flatten" features on the face as much as wider focal lengths.
70mm-200mm...telephoto range - good for "zooming in" to magnify an object. Compression of distance between objects can be noticed at the long end of this range.
200mm-$$$$$mm...super telephoto, limited only by budget.
But remember, focal length is only part of what is important.
Maximum aperture is another big part..the "f-number" that is published behind the focal length e.g. 700-200 f2.8 . To keep it simple, think of a camera lense as a pipe, and light as water.
Because a photograph is nothing more than a record of light that reflected off an object at a particular point and duration of time, the amount of light a lense will "flow" can at times be a very limiting factor. It's not unlike an exhaust system on a motorcycle...bigger is usually better.
We've all seen the front element of a camera lense...the part we see when someone is taking a picture of us. The part most of us never think about is the back end of the lense...out of sight, out of mind.
Maximum aperture refers to the "opening" (it's not really open, but for simplicity's sake) at the back of the lense, which is smaller than the glass in the front. The more "open" the aperture is capable of achieving, the more light we can "flow" through our "pipe". This allows the shutter to open and close faster, which can help us take more photos that are sharply focused. Alternatively, it can allow us to take photos at lower ISO ratings, which can help reduce or eliminate "noise" (similar to film grain) in our photos.
A large maximum aperture can also help us achieve bokeh...the word for that wonderful out of focus background that really gives our two-dimensional photographs depth. Here are a couple of examples:
Or a little more extreme...
To complicate things a bit, aperture numbers are inversely and exponentially related to the actual size of the "opening" in the back of the lense. f1 would be about maximum, though you won't find many lenses in that regime. f1.2 is about the largest you'll find, though it comes with a very high price. Both Nikon and Canon have a 50mm, non zoom lense, with an aperture of f1.8 . These lenses are very affordable and can produce great results for the money.
f2.8 will "flow" twice as much light at f4. f4 will "flow" twice as much light as f5.6 f5.6 will "flow" twice as much light as f8.
f2.8 will "flow" eight times as much light as f8. What does that do for us? Let's say we have an example subject that will require a 1/15th second shutter speed to capture enough light to make a correct exposure. At that shutter speed, it is highly unlikely even the best photographer out there could get consistently sharp photos without using a tripod. Most of us will end up with a blurry mess. Allowing more light to pass through our lense by opening the aperture up to f2.8 will allow us to get the same exposure level by shortening the amount of time the shutter is open to 1/250th of a second. Even after drinking seven cups of coffee most of us could get consistently sharp photos at 1/250.
There is a trade off here, but that is beyond the scope of this writing. For now, keep in mind that the maximum aperture of a lense makes it more useful, in more conditions. The "second number" behind the more popular focal length range is important also.
