Lenses are measured by focal length and different focal lengths effect your images differently. Wide angle lenses have distortion and large depth of fields and Telephoto lenses have compression with shallow depth of fields. By knowing how these different effects take hold in certain focal lengths you can use the affects to your advantage while composing an image.
Focal length is measured in millimeters and determines your lenses angle of view. The angles of view get broken down into three categories Telephoto, Normal, Wide angle and Super Wide wide angle (sometimes four categories when Super wide angle is included) Telephoto lenses are lenses that are “zoomed in”, normal lenses are near to what are eyes see, and wide angle is a larger angle of view than what are eyes see.
For full frame cameras these are the focal length ranges:
Telephoto lenses range from 85mm-300mm (and longer)
Normal range from 40mm-60mm
Wide angle – 24mm-35mm
Super wide- 12mm-20mm
If your camera has a sensor (or film) smaller than full frame, like a cropped sensor your angle of view will be a different. Same goes for larger sensors (or film formats) Meaning your focal length ranges will be different.
Super Wide and Wide angle lenses
Wide angle lenses are very useful for when you don’t have enough room to step back and take the shot. For example I’m in a tiny room at a event and need to get a group shot but I can’t scoot back enough, a wide angle lens comes in handy. However if there isn’t time constraints and other location options to take the group photo, I will try to move the group somewhere to where I can use a normal or telephoto focal length. Why? Distortion. With wide angle lenses what ever is closest to the lens appear larger than whatever is further back in the frame. This is where the phrase the camera adds 10lbs comes from. So group shots and portraits are not usually best with ultrawide angle lenses unless you purposely use the distortion to your advantage.
In this image I used a wide angle lens to make the crawfish appear really big:
Here I used a wide angle to give the appearance that this 2nd Liner was larger than life:
Telephoto lenses have distortion too, but the distortion is opposite of wide angle lenses. It’s called compression. This is when objects in the back ground of the photo appear to be closer than they really are. Look at the bottom of the blog. See in the 200mm shot the fence seems right behind the manakin head. Now look at the 15mm shot the fence looks really far away. This is compression. I find myself using it when shooting portraits and I want my background to be a little closer to my subject. I’ll have to step further back then zoom in.
Here I used a telephoto lens to fill the background with the screen the the presenter was using:
In this image I wanted the background to be filled with my subjects AutoBody Shop. So I took a few steps back and filled the frame.
Here's some photos I took in Palmer Park for this blog post to show the difference in wide angle vs telephoto.
Notice the flag in the back ground, with the wide angle lens the flag looks like its across the park, with the telephoto its right behind him.
Here’s an example of 200mm - 15mm. Notice how the fence starts to get separated as the focal length changes.
So, use focal lengths to your advantage.