Camera Lens 101-Things You Should Know or at Least be Familiar with When Buying a Camera lens

If you are interested in purchasing a really nice camera, there are a few things you should know before you do. Below are some important camera basics to understand so you are a savvy shopper and get the most bang for your buck.

Camera Lenses 101

When it comes to D-SLRs the camera body is one thing and the lens is another. There are two really important aspects when purchasing a lens

1) the mm (millimeters) and

2) the aperture.

Understanding "mm vs zoom": video cameras use "zoom," still camera lenses use "mm"

When it comes to still cameras, the lens "mm" is the zoom. Your eye sees at "50mm" fixed. So 18mm is zoomed further out then your eye sees things. This is great for making a small room look big or taking a picture of a big item without having to walk really far away from it. 135mm could be described as more than double the closeness that your eye sees. Objects will appear much closer and much larger then what your eye sees. (Most outdoor portraits of people are taken at 100mm or more so that the background is out of focus and looks nice.) If you are trying to convert mm to zoom I have heard that you can divide the the mm range to get the zoom. For example 18-135mm lens would be 135/18 or 7.5x zoom. I don't know how accurate that conversion is, but it gives you an idea.

Understanding Camera Apertures: Aperture 101

Aperture is the size of the hole that lets light into the camera. It is a fraction, so it is one divided by the number. The smaller the number the bigger the hole. 1.4f is among the largest possible and is about the size of a 50 cent piece. 29f is about as small as possible about the size of a needle head. Lenses are numbered by the largest possible aperture they can have. That means a 1.4f lens (big aperture) can get as small as a 29 aperture, but you can't have a 5.6f lens (moderate aperture) be a 1.4f. If that doesn't makes sense, don't worry, just keep reading. Remember aperture is a fraction so the smaller the number the bigger the hole and it works exponentially. 1.4f is several times larger than a 3.5f which is several times bigger than a 5.6f.

Things to remember:

1.4 is a huge aperture

5.6 is moderate.  It is nothing to write home about but will work in well-lit areas. Outside 5.6f can take a great picture anywhere...until night time.

Most lenses aren't smaller than 5.6, except perhaps some really huge zoom lenses. Really huge zoom lenses are like 70-200mm or 300mm. This could be good for sports if it is outside and really bright. However, the lens can be really heavy, really big, and often their aperture is small unless you spend thousands of dollars.

A lot of lenses now a days adjust like the one described at the top (18-135mm 3.5-5.6f). That means at 18mm zoomed all the way out the largest aperture possible is 3.5. When I zoom in the largest aperture possible will only be 5.6.