Digital single-lens reflex camera

A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor.

The reflex design scheme is the primary difference between a DSLR and other digital cameras. In the reflex design, light travels through the lens and then to a mirror that alternates to send the image to either a prism, which shows the image in the optical viewfinder, or the image sensor when the shutter release button is pressed. The viewfinder of a DSLR presents an image that will not differ substantially from what is captured by the camera's sensor, as it presents it as a direct optical view through the main camera lens rather than showing an image through a separate secondary lens.

DSLRs largely replaced film-based SLRs during the 2000s. Major camera manufacturers began to transition their product lines away from DSLR cameras to mirrorless interchangeable-lens cameras (MILCs) beginning in the 2010s.

History

See also: History of the camera § Digital cameras

In 1969, Willard S. Boyle and George E. Smith created a new way to capture images using tiny electronic parts. This invention helped make digital photos possible. They received a special award called the Nobel Prize in 2009 for their work.

In the 1970s and 1980s, companies started building cameras that could save pictures digitally instead of on film. These early cameras looked like the old film cameras but used special parts to record images.

Sony showed a new kind of camera in 1981 that used a special disk to save pictures. This was one of the first cameras that didn’t use film.

In 1986, a company called Kodak made a camera that could save digital pictures. This was one of the first real digital cameras.

Over the years, many companies made digital cameras that worked like old film cameras but saved pictures digitally. These are called digital SLRs.

In the late 1990s, Nikon made a professional digital camera that could use the same lenses as their film cameras. This helped digital cameras become popular with professionals.

In the 2000s, more companies started making digital SLRs for everyday users. These cameras became easier to buy and use, so more people could take digital pictures.

Today, digital SLRs are still used by many people, but many companies now make cameras without mirrors, called mirrorless cameras. Nikon and Pentax still make some digital SLRs, while other companies have stopped.

• Nikon offers the flagship full-frame D6, as well as the midrange full-frame D780 and D850 and the entry-level APS-C D7500. As of 2024^[update], all other Nikon DSLRs have been discontinued.
• Leica produces the S3, a medium format DSLR.
• Pentax currently offers APS-C and full-frame DSLRs. The APS-C cameras include the K-3 III and the KF. The K-1 Mark II, announced in 2018 as successor to the Pentax K-1, is the current full-frame model. All APS-C and full-frame models have extensive backward compatibility with Pentax and third-party film era lenses from about 1975, those that use the Pentax K mount.

Design

DSLRs often use interchangeable lenses that fit into a special lens mount. Inside the camera, there is a moving mirror that flips up and down. When you look through the viewfinder, the mirror sends light through a special glass block called a pentaprism or pentamirror, showing you exactly what the lens sees.

To take a picture, the mirror moves out of the way, the focal-plane shutter opens, and the image is captured by the image sensor. After the picture is taken, the mirror moves back, ready for the next shot. This mirror system lets you see a clear, bright preview of your scene before taking the picture.

Autofocus

Main article: Phase detection autofocus

DSLRs usually use a special focusing method called phase detection. This helps the camera quickly find the best focus point. In the past, only SLR cameras could use this method because they needed the same light to reach both the sensor and the focus system. Now, some newer cameras without mirrors can also use phase detection.

Common features

Mode dial

Digital SLR cameras, like most other digital cameras, usually have a mode dial to choose different camera settings or automatic scene modes. Sometimes called a "PASM" dial, they often include modes such as program, aperture-priority, shutter-priority, and full manual modes. Scene modes can change depending on the camera and are less customizable. They often include landscape, portrait, action, macro, night, and silhouette, among others. These different settings can also be set up by adjusting certain camera options.

Dust reduction systems

Main article: Dust reduction system

One way to keep dust out of the camera is by using a "dust cover" filter behind the lens mount. This was first used by Sigma in its first DSLR, the Sigma SD9, in 2002.

Olympus used a built-in sensor cleaning tool in its first DSLR, the Olympus E-1, in 2003, which had a sensor that could be exposed to air.

Several Canon DSLR cameras use a system that shakes the sensor at high speeds to remove dust.

Interchangeable lenses

Main articles: Photographic lens and Lenses for SLR and DSLR cameras

Changing lenses to pick the best one for what you’re taking a picture of is a big reason why DSLR cameras are popular, even though this feature isn’t only for DSLRs. Interchangeable lenses for SLRs and DSLRs are made to fit a specific lens mount, which is usually different for each brand. Photographers often use lenses made by the same company as the camera body, like Canon EF lenses on a Canon camera, but there are also many other companies, such as Sigma, Tamron, Tokina, and Vivitar, that make lenses for different lens mounts. There are also lens adapters that let you use a lens made for one mount on a camera with a different mount, though this can sometimes limit what the lens can do.

Many lenses can be used on modern DSLRs and older film SLRs that use the same lens mount. However, when lenses made for 35 mm film or similarly sized digital sensors are used on DSLRs with smaller sensors, the image gets "cropped," and the lens seems to have a longer focal length than it actually does. Most DSLR makers have created lenses designed for smaller sensors, mostly in the wide-angle range. These lenses might not work fully with full-frame sensors or 35 mm film because of the smaller image circle, and some Canon EF-S lenses can interfere with the mirror inside full-frame cameras.

HD video capture

Since 2008, makers have added a movie mode to DSLRs that can record high-definition video. A DSLR with this feature is often called an HDSLR or DSLR video camera. The first DSLR with HD movie mode was the Nikon D90, which recorded video at 720p24 (1280x720 resolution at 24 frame/s). Other early HDSLRs used unusual video resolutions or frame rates. For example, the Pentax K-7 used a resolution of 1536×1024, matching the imager’s 3:2 aspect ratio. The Canon EOS 500D (Rebel T1i) used a frame rate of 20 frame/s at 1080p, along with a more standard 720p30 format.

Generally, HDSLRs use the whole sensor to capture HD video, though not all pixels are used (which can cause some video issues). Compared to the small sensors in most camcorders, HDSLRs have much larger sensors, giving them different image qualities. HDSLRs can create shallower depth of field and better performance in low light. However, because of how they’re built, HDSLRs often lack some video features found in regular camcorders, such as autofocus while recording, powered zoom, and an electronic viewfinder. These limitations mean HDSLRs need some planning and skill to use for filming.

Video features in HDSLRs have kept improving, with higher resolutions (like 1080p24), better automatic and manual controls, and support for formats used in high-definition TV, Blu-ray discs, and Digital Cinema Initiatives (DCI). The Canon EOS 5D Mark II (with firmware version 2.0.3/2.0.4) and Panasonic Lumix GH1 were the first HDSLRs to offer 1080p video at 24 frames per second, and since then many more models have added similar features.

The growth of HDSLR cameras has led to a new era in digital filmmaking, called the “DSLR revolution.” Many independent filmmakers use the “Shot On DSLR” label. Canon’s TV ads in North America featuring the Rebel T1i were filmed using that camera. HDSLRs are also used in documentary and ethnographic filmmaking because they’re affordable, have good technical and visual features, and allow for very personal filming. More films, TV shows, and other projects are using these improving features. For example, Canon’s “Story Beyond the Still” contest asked filmmakers to shoot a short film in 8 parts, with each part shot over a short time and a winner chosen for each part. After 7 parts, the winners worked together to film the final part. Because HDSLRs are more affordable and smaller than professional movie cameras, The Avengers used five Canon EOS 5D Mark II and two Canon 7D to film scenes from different angles and reduce the need for reshooting complex action scenes.

Makers have created optional accessories to improve DSLRs for video, such as shotgun microphones and external EVF screens with 1.2 million pixels.

Live preview

Main article: Live preview

Early DSLRs couldn’t show the view through the optical viewfinder on the LCD screen — a feature called live preview. Live preview is helpful when the camera’s viewfinder can’t be used, such as in underwater photography where the camera is in a waterproof case.

In 2000, Olympus introduced the Olympus E-10, the first DSLR with live preview, though it had a fixed lens. By late 2008, many DSLRs from Canon, Nikon, Olympus, Panasonic, Leica, Pentax, Samsung and Sony offered continuous live preview. The Fujifilm FinePix S5 Pro allowed 30 seconds of live preview.

On most DSLRs with live preview using the main sensor, the autofocus system that uses phase detection doesn’t work in live preview mode, and the camera switches to a slower contrast system, like in point-and-shoot cameras. Even though phase detection needs contrast to work, contrast-based autofocus can be slower but more accurate.

In 2012, Canon introduced hybrid autofocus to DSLRs with the EOS 650D/Rebel T4i, and later a more advanced version called “Dual Pixel CMOS AF” with the EOS 70D. This technology lets certain pixels do both contrast detection and phase detection, making autofocus faster in live view (though still slower than pure phase detection). While some mirrorless cameras and Sony’s fixed-mirror SLTs have similar systems, Canon is the only one offering this in DSLRs.

A separate software tool from Breeze Systems, called “DSLR Remote Pro v1.5,” introduced in October 2007, allows live view from a distance. It works with the Canon EOS 40D and 1D Mark III.

Sensor size and image quality

Main article: Image sensor format

Image sensors in DSLRs come in different sizes. The largest are used in “medium format” cameras, usually with a “digital back,” which can replace a film back. Because making these large sensors is expensive, these cameras often cost over $1,500 and can reach $8,000 or more.

“Full-frame” sensors are the same size as 35 mm film (24×36 mm). They’re used in DSLRs like the Canon EOS-1D X Mark II, 5DS/5DSR, 5D Mark IV and 6D Mark II, and Nikon’s D5, D850, D750, D610 and Df. Most cheaper DSLRs use a smaller sensor called APS-C, which is about 24×16 mm, slightly smaller than an APS-C film frame, or about 40% of the area of a full-frame sensor. Other sensor sizes in DSLRs include the Four Thirds System sensor at 26% of full frame, APS-H sensors (like in the Canon EOS-1D Mark III) at around 61% of full frame, and the original Foveon X3 sensor at 33% of full frame (though Foveon sensors since 2013 are APS-C sized). Leica has an "S-System" DSLR with a 30×45 mm sensor containing 37 million pixels. This sensor is 56% larger than a full-frame sensor.

The number of megapixels in a DSLR sensor is a measure of resolution. More expensive cameras and those with larger sensors often have higher megapixel counts. But more megapixels don’t always mean better quality. For example, when comparing two APS-C sensors — one with 12.1 MP and one with 18 MP — the one with fewer megapixels usually works better in low light. This is because each pixel is larger and catches more light, compared to a sensor with more pixels. However, this isn’t always true because newer cameras with more megapixels also have better software to reduce noise and higher ISO settings to compensate for less light per pixel.

Depth-of-field control

The lenses used on DSLRs often have a wider range of apertures, from as wide as f/0.9 to about f/32. Lenses for smaller sensor cameras usually don’t go much wider than f/2.8 or much smaller than f/5.6.

Some smaller sensor cameras add an ND filter into the aperture system to help extend the exposure range.

The apertures available on smaller sensor cameras give much more depth of field than similar angles on a DSLR. For example, a 6 mm lens on a 2/3″ sensor camera has a field of view similar to a 24 mm lens on a 35 mm camera. At f/2.8, the smaller sensor camera (with a crop factor of 4) has about the same depth of field as the 35 mm camera set to f/11.

Wider angle of view

Further information: Crop factor

The angle of view of a lens depends on its focal length and the size of the camera’s image sensor; a sensor smaller than 35 mm film (36×24 mm) gives a narrower angle of view for the same focal length than a camera with a full-frame (35 mm) sensor. As of 2017, only a few DSLRs had full-frame sensors, such as the Canon EOS-1D X Mark II, EOS 5D Mark IV, EOS 5DS/5DS R, and EOS 6D Mark II; Nikon’s D5, D610, D750, D850, and Df; and the Pentax K-1. The limited number of full-frame DSLRs is partly because of the cost of such large sensors. Medium format sensors, like those in the Mamiya ZD, are even larger than full-frame (35 mm) sensors and can provide even higher resolution, but they’re even more expensive.

The effect of sensor size on angle of view is called the “crop factor” or “focal length multiplier.” This is the number you multiply the lens focal length by to get the full-frame-equivalent focal length. Typical APS-C sensors have crop factors of 1.5 to 1.7, so a 50 mm lens would act like a 75 mm to 85 mm lens on a 35 mm camera. The smaller sensors in Four Thirds System cameras have a crop factor of 2.0.

While the crop factor of APS-C cameras effectively narrows the angle of view of long-focus (telephoto) lenses, making it easier to take close-up pictures of faraway objects, it reduces the angle of view of wide-angle lenses by the same amount.

DSLRs with “crop” sensors have slightly more depth-of-field than cameras with 35 mm sensors for the same angle of view. The added depth of field can be roughly calculated by multiplying the depth of field by the crop factor. Shallower depth of field is often preferred by professionals for portraits and to make the subject stand out from the background.

Unusual features

On July 13, 2007, FujiFilm announced the FinePix IS Pro, which used Nikon F-mount lenses. This camera could also capture images in infrared and ultraviolet light.

In August 2010, Sony released a series of DSLRs that allowed 3D photography. This was done by moving the camera horizontally or vertically in Sweep Panorama 3D mode. The image could be saved as an ultra-wide panoramic picture or as 16:9 3D photography to be viewed on BRAVIA 3D TV sets.

Comparison with other digital cameras

The main difference between a digital single-lens reflex camera (DSLR) and other digital cameras is its reflex design. In a DSLR, the same light that reaches the camera’s sensor also passes through the viewfinder. This happens using a mirror that flips up and down. When you press the shutter button, the mirror moves out of the way so light can reach the sensor and take the picture.

Other digital cameras, like point-and-shoot cameras, usually show the image on an LCD screen. This screen can be hard to see in bright sunlight. DSLRs show the image through an optical viewfinder, which doesn’t get washed out by sunlight and works very quickly. However, when you use the optical viewfinder, you can’t see the image on the screen at the same time. Some DSLRs now have “live preview,” which lets you see the image on the screen, but older models did not have this feature.