Lenses are a confusing subject for beginners. Focal lengths, different sizes, distortions and many more elements can add to this confusion. Without going into large amounts of detail, we’ll look at a basic run down.
Why Are Some Lenses So Expensive & Others So Cheap?
Some lenses are built very simply with cheaper optic glass and more plastic parts etc. They can still take a nice photo in the right conditions. Expensive lenses have higher quality optic glass (or other synthetic options) elements and the price varies depending on the features they have (such as Image Stabilisation) or how low in aperture the lens can go.
Focal Length
Focal length describes the view the lens is giving. For instance, if you have a zoom lens that zooms from 100mm to 300mm and you are zoomed halfway out then you are using a focal length of 200mm.
Fixed focal length lens don’t zoom and you buy them for the focal length they are. For instance, a 50mm, fixed focal length (or ‘Prime’) lens is a popular choice.
Common Types of Lenses
• Prime – A Prime lens is a lens with a fixed focal length. This means you can’t zoom this lens as it has only one set length. Because there is no need to expect the lens to operate well at different focal lengths, prime lenses tend to be very clear, sharp lenses.
• Zoom - A Zoom lens is a lens that has an adjustable focal length. An example might be a lens that can zoom from 100mm to 400mm. Because of the different focal lengths this lens has to handle there is always a compromise somewhere. For instance, paying $1000 for a lens like this might get you a lens that has a minimum aperture of around f4 or f4.5 and no image stabilization. Paying $2000 might get you a similar lens but with image stabilization and a minimum aperture of f2.8.
• Wide Angle – Wide angle is a general term for shorter focal lengths. A focal length of around 24mm is considered the high end of wide angle. Something around the 15mm is about middle of the range and 10mm is very wide.
• Macro – Macro lenses are lenses designed to get extreme close up shots. Zooming in with a zoom lens is a close up, even when you use a macro feature on your DSLR. A macro lens allows you to get in much closer. A good macro lens would let you get a clear photo of the hairs on a fly’s back.
• Fisheye – Fisheye lenses are another specialty style lens like the macro lens and distortion is the name of the game here. Fisheye lenses purposely bend the scene around to show more than the human eye is capable of.
The view can be as wide as 180 degrees which is like having eyes that start at your nose and finish at your ears!
A Canon L Series Lens
Canon L Series Lens
Distortions
Sometimes when you view your photos you will notice some odd distortion in them especially when photographing something like buildings.
You notice that the buildings in the middle of the photo may be ok but those on the outside of the photo are well out of perspective and leaning inwards toward the centre of the photo.
Most lenses suffer from this distortion although cheaper lenses are more prone to the problem. The look can actually be kind of cool but not if you are trying to capture a photo that is true to your eyes view.
When photographing a building close up and, let’s say, shooting up the building, then the sides of the building will indeed slope in towards centre of frame and will look that way to your eye also. Obviously this makes for a dramatic photo in most cases.
However, when you are shooting from a distance you usually want the building to look more upright.
This distortion is more apparent when using wider angle lenses with their shorter focal lengths than with longer lenses and longer focal lengths.
The photos below show how distortion can show up and how some editing in photo software on your computer can solve the problem.
Here we see the shot as it was taken. Note the buildings leaning inwards.
Lens Distortion
Here’s the same shot edited with a distort tool that straightened the buildings.
Lens Distortion Corrected
