Back to class with focal lengths
It has been a while since the last post from my series on the basic of photography but better late than never. In this post I am going to talk about focal lengths and how they affect the photographs we take. Once you have decided shutter speed, aperture and ISO you have to think about which lens to use. It seems like this would be super easy; you either use the lens that gets you close to the subject or is wide enough to let you get the full picture. To some extent this is true but this is not the full story. So let’s start by looking at the different types of lenses.
First let’s talk a little about what is the standard lens. The standard lens is one that sees as close as possible to what our eyes see. For a 35mm full frame camera this is a 45mm to 55mm. Any lens that brings you closer to the subject or makes you farther away is not a standard lens. (Note: If the camera has a smaller or larger sensor/film size then conversions must be done to know what length lens is equivalent to our eyes. For example on many modern DSLRs the sensor is smaller than the original size of 35mm from the film days. These cameras are normally said to have a APS-C sized sensor and around 35mm lenses are equivalent to what our eye sees. For this lesson we will stayed focused on full frame cameras.)
Looking a the picture above we can see that the person on the bike has been magnified or pulled closer to the camera with a telephoto lens. Telephoto lenses are lenses that are longer than 55mm and magnify the subject. An few interesting things to consider when using a telephoto lens is that it not only magnifies but also compresses the object in the photo and creates a shallow depth of field. In the picture above the sensation is that the bike is surrounded by cars that are really close to it and that the rider is in focus but the cars behind are starting to go out of focus. Because of the magnification less light is allowed in and the shutter speed normally needs to be higher than 1/60th of a second to get a picture without a blur. If the focal length is 100 the shutter speed should be about the same or higher. This photo was taken at F5.6, shutter speed of 1/125 (a little slow for the focal length) ISO 200 and focal length of 450mm.
A wide angle lens one that is less than 45mm. It does the oposite of the telephoto lens by expanding what you can see, giving you more depth of field letting in more light and spreading the objects out in the image to appear as if they are farther apart than they really are. It also tends to distort the image some what. This distortion can be nice at times but the wider you go the more it becomes surreal. In the photo above it looks like his hand is enormous, almost larger than his body. This photo was taken with at f5, shutter speed of 1/200 of a second, ISO 200 and a focal length of 18mm.
You might be saying, “hey I have a zoom lens that is 18mm to 70mm, so is a wide angle, standard, or telephoto?” Well, lucky you, it is all. This is the great advantage to zoom lenses, they cover a large range. The problem with zooms is that they are usually slower (not wide aperture, like a max of f4.5), more expensive, and have lower image quality. Of course there are some very good zooms but they are usually super expensive. Also, there is one other not so obvious, disadvantage to zooms. When working with a fixed lens (non-zoom), you move your body for the picture and it forces you to see the shot from a different angle and a different perspective. This can really be helpful when trying to improve your composition. Far too often with zooms your feet are frozen and you just spend the lens and as you know telephotos compress and wide angles distort so moving your feet with a 50mm helps you to prevent either of this.
In the end it really depends on what you are after and knowing how your lenses affect the outcome is key.
To get a better idea how focal length changes your photos take a look at this link!