London School of Photography Blog

Photography tip: Introduction to lenses


In other words, the lens you have right now on your DSLR is pretty darn good for your normal day-to-day shooting. But, in that case you may ask, why do professional photographers pay thousands of pounds on top of the line lenses? Well, it simply has to do with three very important things: Durability, aperture, and sharpness. But before we get into all that let’s start from the beginning.
Lenses are there to focus the light onto the sensor of the camera, and to change your angle of view. Most lenses are interchangeable, allowing photographers to put then on or take them off the camera depending on what they are trying to photograph.
Other lenses are permanently attached to your camera and are not removable, meaning you only have one angle of view, something that purists, like street photographers love.
Focal length 
The number or numbers on the side of your lens, like 18-55mm for example, or 50mm, indicate the focal length of your lens, or how wide or narrow your field of view is. The lower the number, like 18mm for instance, the wider the field of view and the further your subject appears to be from your lens. The bigger the number, like 300mm for example, the narrower the field of view, and the closer your subject is to your lens.
Anything above 50mm makes your lens a telephoto lens, and anything below 50mm makes it a wide-angle lens. Lenses with focal lengths lower than 16mm are usually referred to as fish-eye lenses, as they look like fish-eyes. These lenses give you an extremely wide angle of view, making them useful for architecture photography. Not a particularly flattering lens when used on people as they tend to comically distort people especially at the edges of the frame.
Wide angle lenses are good for photographing landscapes and buildings, whereas telephoto lenses are used for sports, portrait, and even space photography as they allow the photographer to bring their subject extremely close to them.
Zoom Lenses 
Most lenses, like the ones that came in your camera kit are zoom lenses, meaning that you can change the focal length by zooming in and out, like your 18-55mm lens. When you zoom in you turn you are increasing the focal length number and bringing your subject closer to you while you narrow your field of vision. When you zoom out, you decrease your focal length thereby widening your field of view, and taking your subject further away from your lens.
Zoom lenses are very versatile, as you can quickly zoom in or out to capture a fleeting moment, making them popular with photographers who don’t like to carry a lot of equipment around, like news photographers.
Prime Lenses 
There are lenses that have a single focal length like 24mm, 35mm, 50mm, 300mm etc. These lenses are called prime lenses and if you want to get closer or further to your subject, you will have to use your feet! Prime lenses are sharper than zoom lenses due to the fact that they have fewer elements inside, and they are also faster lenses, meaning they come with wider apertures. Wider apertures let in more light allowing photographers to use faster shutter speeds and shoot in low light conditions. They are also cheaper than zoom lenses, depending on what you are buying. A 50mm f1.8 Canon lens costs around £120! Prime lenses are popular with fashion, street, wedding, and documentary photography due to their incredible sharpness and wide apertures.
The Standard Lens 
The old faithful, the choice of the most purist of street photographers, the 50mm lens is called a standard lens because the angle of view it gives the photographer is very similar to what we actually see. So legendary photographers like Henri Cartier-Bresson would only shoot with a 50mm lens because any other focal length would distort reality as the photographer would see it with his own eyes.
Focusing Distance 
If you look on the side of your 18-55 lens you will see a little shape of a flower, and next to that 0.28m. That is the closest distance to your subject that the lens can focus. Focusing distance is measured from the focal plane mark on the camera body, not the lens itself.
If you want to photograph insects or other then you need to buy a macro lens which is specifically designed to be able to to get really close to small objects.
So what makes professional lenses more expensive?
Well, the first thing is aperture. Aperture, like the pupil of your eye is found inside the lens and it controls the amount of light that hits the sensor. The wider the aperture, the more light will hit he sensor, meaning that photographers can work in low light conditions without getting camera shake. Wider apertures also help to blur the area behind the subject allowing the photographer to separate the subject from a busy background.
The lower the number of the aperture, for example f1.8, the wider the aperture (bigger hole, more light, more blur), and the higher the number of the aperture, for example f22 the smaller the aperture (small hole, less light, more sharpness).
If you look on the side of your kit lens (your 18-55mm lens for example) you will see the numbers f3.5-5.6. That means that the widest aperture you have on your lens is f3.5, which is not bad, but the problem is that when you zoom in, your aperture automatically closes to f5.6, meaning less light is now hitting the sensor, and could result in camera shake if you are shooting in low light.
Professional zoom lenses on the other hand will have an aperture of f2.8 that doesn’t close when you zoom in or out, meaning that photographers can shoot in low light conditions with less camera shake. A professional zoom lens, like a canon 24-70mm f2.8 lens costs around £1740, and yes, it’s worth every penny.
Other things that make professional lenses more expensive are durability. Kit lenses are usually plastic and have a lower shelf-life than professional lenses that are made of metal. Professional lenses are also sharper and also dust and water resistant.
On our next blog we will talk more in-depth about the different types of lenses and their uses.

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