Learning about Lenses

Today I'm changing it up a little bit.   As one reader mentioned, I've talked about the exposure triangle, but on the pictures I post, I also mentioned the focal length, but I really haven't talked about what it means.

Your lens or lenses are critical to your overall photography capability.   In fact, your lens purchases are probably more critical than your camera body purchase(s).   That may sound funny, but the truth is your lenses will outlast your camera bodies.  They also provide you with all the flexibility in what you photograph.  There are two main types of lenses: Zoom and Prime.   The one you are most likely familiar with is the zoom lens.   A zoom lens has a range of focal lengths whereas a prime has only one length.

So what is focal length?  

In the easiest term it is the distance a lens takes to bring a light rays into focus.   If you don't remember this after this point, don't worry.   What you do need to know is that the shorter focal lengths provide a wider angle of view and longer lengths provide a narrower point of view.   What this means is a wide angle lens shows more across the field of view.  However a telephoto lens (with a long focal lengths) acts like a telescope and allows you to "get close" to things that are further away.  

How is focal length measured?

Focal length is measured in millimeters.  You can typically find this listed on your lens.  Many common kit lenses are 18mm - 55mm zoom lenses.   Sometimes you may buy a second lens in your initial kit that might be 55mm - 200mm zoom lens.  Given the range of these two lenses, you have something at the wide angle side, 18mm, and something telephoto at 200mm.   To grasp the effect of this simply look into your viewfinder and zoom in and out with your lens.  When you see a wide field of view, you are at the lower end, and when you see things closer up you are at the telephoto end of the lens.

Typical ranges you see in most lenses are from 10mm (very wide) to 300mm.   That being said, you can buy lenses beyond 300mm.  In fact some ultra-expensive telephoto lenses go to 800mm.  You can also go wider than 10mm, but those are typically fish-eye lenses.

24mm  f/4  ISO 12800  1/320 second exposure

This is an example of a wider lens.  It is shot at 24mm in order to capture a wide field of view.  There were a number of balloons spread across a field all lighting up at the same time.

400mm  f/5.6  ISO 100  1/1000 second exposure

This is an example of a telephoto shot taken of two Herons from very far away.  In order to get the picture I needed to use a very long lens (400mm).   You can see how the longer focal length helps brings object closer in view (magnification effect.)

Prime Lenses

Now that we understand a little more about focal length (and a bit about zoom lenses), what about Prime lenses?

A prime lens has a fixed focal length.  A very common prime lens is a 50mm.   With a prime lens you cannot zoom in and out.  You may wonder why someone would want a prime lens...   There are two key benefits (typically) to prime lenses.   The first is that they tend to be optically better than zoom lenses.  Since there are fewer moving pieces of glass within the lens, they are more precise.  This means they tend to be sharper, often have better contrast, and less distortion.   The second is they are often faster lenses.  Faster???  This mean that their aperture value goes LOWER than you find in zoom lenses.   A very fast zoom lens goes to a maximum aperture of f/2.8.  A very fast prime might go down to f/1.4.   That's two full stops of additional light!!  (note: some do go even lower but those are pretty darn expensive!)

Although I mentioned a 50mm lens, and that's one I often recommend, there are many different primes available.   They start at the ultra wide and go to the super-telephoto.   For you sports fans, you see those huge white lenses on the sidelines of football games?  Those are super-telephoto prime lenses.  They are fast (f/2.8 or f/4) and long (300mm - 500mm).   And let me tell you, they are not cheap.  I know I personally have some lens envy with those. 

Specialty lenses

Above and beyond the zooms and telephotos I describe above, there are specialty lenses available too.   One of my favorites is a macro lens.  A macro lens allows you get get really close to objects so you can get ultra-closeups.   

100mm  f/11  ISO 320  1/100 (flash used)

The above photo was taken with a 100mm macro lens.  (You need to be EXTREMELY careful when photographing bees/wasps/hornets!)   I was literally only a few inches away from the wasp nest when I took this photo.  With these macro lenses you can see incredible details of small objects that you would not be able to see with the naked eye.

Another specialty lens is a tilt-shift lens.  These are quite unique in that the front element actually shifts allowing you to change the focal plane.   What's great with these lenses is you can use them to make normal objects look miniature.

The above picture is actually a full-size locomotive.  You can see how the tilt-shift effect makes the train look like a toy.  Pretty cool effect if you ask me.

You can see through these examples how your choice in lens can effect what types of photos you are able to take.   As you develop your skills you may also develop a desire to take certain types of photos.   For instance, if you like wildlife, you will likely want a longer lens so you can capture animals from a distance.  Or, if you like portraits, you will likely want a mid-range zoom like a 24-70mm lens, or perhaps a nice prime like a 50mm or 85mm.   If you like to photograph insects, flowers, snowflakes, or other small objects, then macro lens is a great choice.

One thing I would recommend is talk with other photographers in your area.  If you are shooting with the same body as they are, you might be able to borrow lenses to get a feel for what you like before you buy.   Lenses aren't cheap, but they are great investments for this hobby.