The background appears soft and out of focus. You can use this effect artistically to blur out distracting details and focus attention on the subject.

How doglassesworkfor nearsighted

In this documentary shot, a deep depth of field is necessary to clearly show what's happening as a ‘coasteering’ man jumps into the sea on the coast of Northern Ireland.

After your eye doctor gives you a written prescription for eyeglass lenses, go to an optician to pick out frames and buy your glasses. Your eye doctor may have an optician working in their office. You can also find opticians in stores that sell glasses and contacts.

How doglassesworkrefraction

A deeper depth of field is used in this portrait of Jane Hill in the London BBC newsroom. The field isn't so deep that the newsroom's pin-sharp, distracting from the subject. But it's clear enough to show where Jane works, which is part of the story.

A deep depth of field is used to keep the background in fairly good focus as well as the subject in the foreground. This is because the background is rather lovely – too good to miss. It contributes to the story.

how doglassesworkfor short-sightedness

A large Sensor makes a shallow depth of field You can use a camera with a large sensor to create a shallow depth of field, but be aware that you'll need to take extra care with focus.

A large aperture makes a shallow depth of field You can use a large aperture to create a shallow depth of field, but be aware this will also increase exposure.

A long focal length makes a shallow depth of field. You can use a long lens to create a shallow depth of field, but be aware this will also restrict your field of view.

Reading glasses can help people with presbyopia read or see things up close. You can buy reading glasses at drug stores and convenience stores. Even though you can get reading glasses without a prescription, it’s important to get regular eye exams to make sure you’re seeing as clearly as possible.

How doglassesworkPhysics

Eyeglass lenses work by bending light — just like the lens and cornea in your eye. The eyeglass lens bends light to make it focus correctly on your retina (the light-sensitive layer of tissue at the back of the eye). Different eyeglass lenses can correct different errors caused by problems with the cornea, lens, or shape of the eye.

When you focus an image using a focusing ring, you're moving the lens so the focal point is in line with the film, in a film camera, or sensor, in a digital camera. (This diagram shows an image that's out of focus).

How doglassesworkto correct vision

If you wear eyeglasses, get an eye exam regularly — as often as your eye doctor recommends. That way, your doctor can make sure you’re still seeing clearly.

Multifocal prescription lenses correct both near and distance vision. They can help people who have trouble seeing things up close and far away. For example, people who have both presbyopia and nearsightedness can use multifocal lenses for reading and driving.

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The distance between the principal focal point and the lens is the focal length. So a 14mm lens bends light so it converges 14mm from the lens. A long lens (200mm) bends the light so it converges 200mm from the lens.

The foreground appears soft and blurry. You can use this blurring, known as bokeh, to focus attention on the subject behind and create a soft and moody foreground.

How doglassesworkfor astigmatism

How doglassesworkdiagram

When this distance is large the depth of field is said to be wide or deep. When it's small the depth of field is shallow or narrow.

Guide to depth of field designed for those new to self-shooting, covering focus, focussing distance, focal length, aperture and sensor.

When there's a big distance between the things that look crisp and sharp, it's known as a wide or deep depth of field. When there's a short distance the depth of field is shallow or narrow.

Single vision prescription lenses correct near vision or distance vision, but not both. If you have nearsightedness, single vision lenses can help you see things far away. If you have farsightedness, they can help you see things up close.

A shallow depth of field has been used to draw attention to the subject, garden designer Mark Lane. The background (Geffrye Museum Garden) is blurred to create a pleasing artistic effect.

A wide shot with a deeper depth of field showing the context in which junior doctors are operating. Here the background is pin-sharp, as well as the subject in the foreground.

Glasses make your vision clearer while you’re wearing them — but they don’t change your eyes at all. Wearing glasses doesn’t make your eyes weaker or your vision worse.

You'll need to change the focusing distance when you experiment with different lenses to create different depths of field. This basically means you have to move.

Eye doctors can prescribe eyeglasses as part of a regular eye exam. The vision test is simple and painless. Your doctor will ask you to read letters that are up close and far away. Then they may give you some eye drops to dilate (widen) your pupil and check the health of your eyes.

The ability to use depth of field creatively is one of the most useful tools in a photographer's skill set. This guide is for beginners in self-shooting, especially those who intend to do further stills and video training with the BBC Academy.

Lenses are known by their focal lengths - 14mm, 50mm, 200mm. Their role is to bend the rays of light that enter through the aperture so they converge into a neat point at the back of the camera.