The name of reflex comes from the fact that these types of cameras use a mirror that reflects ( reflex ) the light coming from the scene and directs it towards the viewfinder (towards the photographer’s eye).

When the shot occurs, the mirror rises, that is, it rotates upwards so that light can reach the electronic sensor (or the film in the case of analogue SLR cameras).

Once the mirror lifted, the shutter released time determined by the photographer, to let in the correct amount of light. That light reaches the electronic sensor and is transformed first into an electrical signal and then into a digital value (a number that indicates how bright each point in the image is)

See how the sensor of a reflex camera works

In an SLR the scene that the photographer sees through the optical viewfinder is the same that the camera will take, there are no parallax errors since both the sensor and the viewfinder display the same frame from the same point of view (both collect light coming through the lens).

The image that reaches the sensor inverted concerning the scene (the upper part comes out downwards, and the lower part rises upwards). For the photographer to see the scene correctly, the optical viewfinder uses a pentaprism or a pentamirror with which it is possible to invert 180º the image that comes from the lens. The mechanism of the pentaprism is what gives it that hump or bulge look on top of SLR cameras.

DSLR cameras are practically the same as analogue cameras when it comes to optics and mechanics.

Features of a reflex camera

Currently, a DSLR camera has several minimal features:

Optical viewfinder

The photographer has a direct vision of the scene through the mirror and prism mechanism (pentaprism or pentamirror depending on the make and model).

For many photographers, the optical viewfinder is essential, because it offers a very clear view of the scene, directly through the lens. And by the fact of completely isolating and thus allowing to focus attention exclusively on the frame, without distractions.

Dedicated phase-detection focusing system

It is a system with an independent sensor and a secondary mirror that depends on the primary mirror. It is only operational in photography (not in video). It is a high-speed autofocus system.

Interchangeable lenses

The camera itself is the ‘body’, and the lens mounted on that body. The photographer can choose between different lenses, the one that best suits the scene he wants to photograph.

Manual mode

Full control of different camera parameters: 

  • Sensitivity
  • Shutter 
  • Speed
  • Aperture.

It is what is known as manual mode, which gives the photographer the possibility to choose how he wants to take each photograph freely.

RAW format

All DSLR cameras currently can record photos in RAW format.

This format allows image information to be stored as it leaves the sensor, without being processed by the camera and without loss of data due to compression, etc.

Furthermore, the RAW format stores the parameters with which the image was taken.

RAW images are like a film negative. They cannot be used directly for publishing, they must learn first developed, and then they can be exported to standard formats such as JPEG.

The main advantage of the RAW format is that it is the photographer who has control and can decide how to develop and process their image.

In English, DSLR cameras are called DSLRDigital Single Lens Reflex

In general, SLR cameras are the most complete and advanced: image quality, focus, ergonomics (grip, buttons, and controls), functions, and aids to the photographer, battery life, optics available.

What SLR camera to buy

SLR cameras sometimes called ‘ professional cameras ‘, to distinguish them from other types of cameras, such as pocket compacts or superzoom (bridge) compacts.

But keep in mind that this name does not make sense: the cameras are not professional. Cameras are tools. Sometimes they are used by professional photographers and other times by amateur photographers.

There are ranges, within the catalogue of SLR cameras, which aimed at the professional sector. This ‘professional range’ designed to meet the needs of a photographer (who makes a living taking photos or videos and depends on his equipment) in many different circumstances, sometimes in very adverse situations.

Here you can see what differences are usually between the cameras of intermediate ranges and the cameras of professional fields.

Other types of digital cameras:

EVIL / mirrorless / mirrorless cameras

They have practically the same characteristics as the SLR cameras but without an optical viewfinder (therefore they do not need a movable mirror, pentaprism and all the internal mechanical part that the SLRs use)

The framing of the scene is done directly from the rear screen or through an electronic viewfinder.

Today it is challenging to talk about the advantages and disadvantages of mirrorless cameras compared to SLRs; rather, it is about comparing specific models of both SLR and EVIL.

  • Some EVIL cameras are smaller and lighter than the typical SLR camera.
  • Mirrorless cameras have fewer moving parts (the entire mirror mechanism has to go up and down with every shot)
  • Some photographers prefer DSLR optical viewfinders, although EVIL electronic viewers are impressive today and offer much more scene information
  • EVIL cameras usually have a higher battery drain: the electronic viewfinder and the sensor are working all the time when the camera is active. In contrast, in SLRs (when we use the optical viewfinder) the sensor only works when making the Photo.

EVIL cameras are also interchangeable lens cameras.

More information about mirrorless cameras and recommended models

Compact cameras

Compact cameras are those that do not allow lens swapping. They manufactured with a specific lens that is what the camera always operates.

They also do not include an optical viewfinder (reflex). Therefore, do not have a movable mirror.

In the compact camera category, there is a massive range of features and benefits.

There are excellent mid-range compact cameras, with a minimal and light format, high-quality optics, and many of the functions that SLR cameras include (for example the possibility of working in manual mode, the option of recording in a RAW format … )

You can also find high-end compact cameras, with features very similar to larger cameras, but in a small and light format perfect for travel or to carry the camera in your pocket.

The compact high – end usually include a much bigger sensor, 1 inch or higher, which makes that provide outstanding image quality, especially in light situations where small sensor compact would begin to show its limitations.


 The so-called high-end or compact superzoom bridge cameras.

These cameras have a format similar to SLRs in terms of size and weight. The optics are designed for each model and cannot be interchanged. They typically include lenses with an extensive zoom range that ranges from wide-angle (full) frames to extreme telephoto (long-range)

They are widely used cameras for photography of birds and nature (wild animals).

They are also the right choice for travel photography because the focal range of the lens covers all situations virtually.

They are usually cameras with a small sensor. Therefore they have certain limitations in low light situations.

Check out this quick guide to see what type of camera best suits your needs.



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