Sony a9

35mm AF digital mirrorless camera

Specification

Production details:
Announced:April 2017
System: Sony E (2013)
Format:
Maximum format:35mm full frame
Imaging sensor:35.6 × 23.8mm CMOS sensor
Resolution:6000 × 4000 - 24 MP
Sensor-shift image stabilization:Yes
Mount and Flange focal distance:Sony E [18mm]
Shutter:
Type:Focal-plane
Model:Electronically controlled
Speeds:30 - 1/32000 + B
Exposure:
Exposure metering:Through-the-lens (TTL), open-aperture
Exposure modes:Programmed Auto
Aperture-priority Auto
Shutter-priority Auto
Manual
Physical characteristics:
Weight:673g
Dimensions:126.9x95.6x73.7mm

Manufacturer description

NEW YORK, Apr. 19, 2017 – Sony Electronics, a worldwide leader in digital imaging and the world’s largest image sensor manufacturer, has today introduced their new revolutionary digital camera, the α9 (model ILCE-9).

The most technologically advanced, innovative digital camera that Sony has ever created, the new α9 offers a level of imaging performance that is simply unmatched by any camera ever created – mirrorless, SLR or otherwise.

The new camera offers many impressive capabilities that are simply not possible with a modern digital SLR camera including high-speed, blackout-free continuous shooting3 at up to 20fps4, 60 AF/AE tracking calculations per second 10, a maximum shutter speed of up to 1/32,000 second8 and much more. These are made possible thanks to its 35mm full-frame stacked Exmor RS™ CMOS sensor – the world’s first of its kind – which enables data speed processing at up to 20x faster than previous Sony full-frame mirrorless cameras11. This unique sensor is paired with a brand new, upgraded BIONZ X processing engine and front end LSI that maximizes overall performance.

This industry-leading speed and innovative silent shooting7 is combined with a focusing system that features an incredible 693 phase detection AF points. Covering approximately 93% of the frame, the focusing system ensures that even the fastest moving subjects are reliably captured and tracked across the frame.

The new α9 also features a vibration free, fully electronic, completely silent anti-distortion shutter7 with absolutely no mechanical mirror or shutter noise, making it an extremely powerful photographic tool for any shooting situation that demands quiet operation. To ensure maximum usability and reliability, the camera features a new Z battery with approximately 2.2x the capacity of W batteries, as well as dual SD media card slots, including one that supports UHS-II cards. An Ethernet port (wired LAN terminal) is available as well, and there is a wide variety of new settings, controls and customizability options that are essential for working pros.

“This camera breaks through all barriers and limitations of today’s professional digital cameras, with an overall feature set that simply cannot be matched considering the restrictions of mechanical SLR cameras” said Neal Manowitz, Vice President of Digital Imaging at Sony Electronics. “But what excites us most about the α9 – more than its extensive product specs – is that it allows professionals to see, follow and capture the action in ways that were never before possible, unlocking an endless amount of new creative potential.”

A New Standard of Speed and Focusing Accuracy

Critical to the record-breaking speed of the new α9 is the combination of the new stacked 24.2 MP2 Exmor RS image sensor, new BIONZ X processor and front end LSI.

The immense processing power from these new components allows for faster AF/AE calculation while also reducing EVF display latency. The processor and front end LSI are also responsible for the larger continuous shooting buffer, enabling photographers to shoot at a blazing 20 fps4 with continuous AF/AE tracking for up to 362 JPEG6 or 241 RAW5 images.

The camera’s innovative AF system tracks complex, erratic motion with higher accuracy than ever before, with the ability to calculate AF/AE at up to 60 times per second10, regardless of shutter release and frame capture. Further, when the shutter is released while shooting stills, the electronic viewfinder functions with absolutely no blackout, giving the user a seamless live view of their subject at all times 12. This feature truly combines all of the benefits of an electronic viewfinder with the immediacy and “in the moment” advantages that not even the finest optical viewfinders can match, and is available in all still image modes including high speed 20 fps4 continuous shooting.

With 693 focal plane phase detection AF points covering approximately 93% of the frame, the camera ensures improved precision and unfailing focus in scenes where focus might otherwise be difficult to achieve. The Fast Hybrid AF system – pairing the speed and excellent tracking performance of phase detection AF with the precision of contrast AF – achieves approximately 25% faster performance when compared with α7R II, ensuring all fast-moving subjects are captured.

Professional Capabilities in a Compact Body

Sony’s new full-frame camera is equipped with a variety of enhanced capabilities that give it a true professional operational style.

The α9 features an all-new, high-resolution, high-luminance Quad-VGA OLED Tru-Finder with approximately 3,686k dots for extremely accurate, true-to-life detail reproduction. The new Tru-Finder, which is the highest resolution viewfinder ever for a Sony α camera, incorporates an optical design that includes a double-sided aspherical element, helping it to achieve 0.78x magnification and a level of corner to corner sharpness that is simply outstanding. The EVF also utilizes a ZEISS® T* Coating to greatly reduce reflections, and has a fluorine coating on the outer lens that repels dirt.

This all adds up to a luminance that is 2x higher than the XGA OLED Tru-Finder from the α7R II, creating a viewfinder image with a brightness level that is nearly identical to the actual scene being framed, ensuring the most natural shooting experience. The frame rate of the Tru-Finder is even customizable, with options to set it for 60 fps or 120 fps13 to best match the action.

The α9 is equipped with an innovative 5-axis image stabilization system that provides a shutter speed advantage of 5.0 steps 9, ensuring the full resolving power of the new sensor can be realized, even in challenging lighting. Also, with a simple half press of the shutter button, the effect of the image stabilization can be monitored in the viewfinder or on the LCD screen, allowing framing and focus to be accurately checked and continually monitored.

The α9 also offers an Ethernet port (wired LAN terminal), allowing convenient transfer of still image files to a specified FTP server at high-speed, making it an ideal choice for studio photography, high-profile news and sporting events and more. There is a sync terminal as well, enabling external flash units and cables to be connected directly for convenient flash sync.

New Features for Fast Operation

Sony’s new α9 has several new and updated focus functions that support faster, easier focusing in a variety of situations. The camera features a multi-selector joystick on the back of the camera, allowing shooters to easily shift focus point within the frame by pressing the multi-selector in any direction up, down, left or right when shooting in Zone, Flexible Spot or Expanded Flexible Spot focus area modes. The new model also offers touch focusing on the rear LCD screen for easily selecting of and shifting focus towards a desired focus point or subject.

New for Sony E-mount cameras, the α9 includes the addition of separate drive mode and focus mode dials, plus a new “AF ON” button that can be pressed to activate autofocus directly when shooting still images or movies.

Additional new capabilities include the “AF Area Registration”, which allows frequently used focus area to be memorized and recalled via custom button assignments. There is also the ability to assign specific settings (exposure, shutter speed, drive mode, etc) to a custom button to be instantly recalled when needed. The camera can memorize and automatically recall the last focus point used in a vertical or horizontal orientation as well, instantly switching back to it when that specific orientation is used again.

For enhanced customization, a “My Menu” feature is available, allowing up to 30 menu items to be registered in a custom menu for instant recall when needed.

Double Battery Life, Double Memory

The innovative α9 camera features an all-new Sony battery (model NP-FZ100) with 2.2x the capacity of previous Sony full-frame models, allowing for much longer shooting performance.

Also, based on extensive customer feedback, the new camera offers two separate media card slots, including one for UHS-II media. The same data can simultaneously be recorded to both cards, or the user can choose to separate RAW / JPEG or still images / movies. Movies can also simultaneously be recorded to two cards for backup and more efficient data management.

High Sensitivity and Wide Dynamic Range

The unique design of the α9 image sensor represents the pinnacle of Sony device technology. The 24.2 MP 2 full-frame stacked CMOS sensor is back-illuminated, allowing to capture maximum light and produce outstanding, true-to-life image quality. The sensor also enables the diverse ISO range of 100 – 51200, expandable to 50 – 20480014, ensuring optimum image quality with minimum noise at all settings.

The enhanced BIONZ X processor plays a large part in image quality as well, as it helps to minimize noise in the higher sensitivity range while also reducing the need to limit ISO sensitivity in situations where the highest quality image is required.

The new α9 also supports uncompressed 14-bit RAW, ensuring users can get the most out of the wide dynamic range of the sensor.

4K Video Capture

The new α9 is very capable as a video camera as well, as it offers 4K (3840x2160p) video recording across the full width of the full-frame image sensor15, 16. When shooting in this format, the camera uses full pixel readout without pixel binning to collect 6K of information, oversampling it to produce high quality 4K footage with exceptional detail and depth. Recording is also available in the popular Super 35mm size.

Additionally, the camera can record Full HD at 120 fps at up to 100 Mbps, which allows footage to be reviewed and eventually edited into 4x or 5x slow motion video files in Full HD resolution with AF tracking17.

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Copyright © 2012-2024 Evgenii Artemov. All rights reserved. Translation and/or reproduction of website materials in any form, including the Internet, is prohibited without the express written permission of the website owner.

Chromatic aberration

There are two kinds of chromatic aberration: longitudinal and lateral. Longitudinal chromatic aberration is a variation in location of the image plane with changes in wave lengths. It produces the image point surrounded by different colors which result in a blurred image in black-and-white pictures. Lateral chromatic aberration is a variation in image size or magnification with wave length. This aberration does not appear at axial image points but toward the surrounding area, proportional to the distance from the center of the image field. Stopping down the lens has only a limited effect on these aberrations.

Spherical aberration

Spherical aberration is caused because the lens is round and the film or image sensor is flat. Light entering the edge of the lens is more severely refracted than light entering the center of the lens. This results in a blurred image, and also causes flare (non-image forming internal reflections). Stopping down the lens minimizes spherical aberration and flare, but introduces diffraction.

Astigmatism

Astigmatism in a lens causes a point in the subject to be reproduced as a line in the image. The effect becomes worse towards the corner of the image. Stopping down the lens has very little effect.

Coma

Coma in a lens causes a circular shape in the subject to be reproduced as an oval shape in the image. Stopping down the lens has almost no effect.

Curvature of field

Curvature of field is the inability of a lens to produce a flat image of a flat subject. The image is formed instead on a curved surface. If the center of the image is in focus, the edges are out of focus and vice versa. Stopping down the lens has a limited effect.

Distortion

Distortion is the inability of a lens to capture lines as straight across the entire image area. Barrel distortion causes straight lines at the edges of the frame to bow toward the center of the image, producing a barrel shape. Pincushion distortion causes straight lines at the edges of the frame to curve in toward the lens axis. Distortion, whether barrel or pincushion type, is caused by differences in magnification; stopping down the lens has no effect at all.

The term "distortion" is also sometimes used instead of the term "aberration". In this case, other types of optical aberrations may also be meant, not necessarily geometric distortion.

Diffraction

Classically, light is thought of as always traveling in straight lines, but in reality, light waves tend to bend around nearby barriers, spreading out in the process. This phenomenon is known as diffraction and occurs when a light wave passes by a corner or through an opening. Diffraction plays a paramount role in limiting the resolving power of any lens.

Doublet

Doublet is a lens design comprised of two elements grouped together. Sometimes the two elements are cemented together, and other times they are separated by an air gap. Examples of this type of lens include achromatic close-up lenses.

Dynamic range

Dynamic range is the maximum range of tones, from darkest shadows to brightest highlights, that can be produced by a device or perceived in an image. Also called tonal range.

Resolving power

Resolving power is the ability of a lens, photographic emulsion or imaging sensor to distinguish fine detail. Resolving power is expressed in terms of lines per millimeter that are distinctly recorded in the final image.

Vignetting

Vignetting is the darkening of the corners of an image relative to the center of the image. There are three types of vignetting: optical, mechanical, and natural vignetting.

Optical vignetting is caused by the physical dimensions of a multi-element lens. Rear elements are shaded by elements in front of them, which reduces the effective lens opening for off-axis incident light. The result is a gradual decrease of the light intensity towards the image periphery. Optical vignetting is sensitive to the aperture and can be completely cured by stopping down the lens. Two or three stops are usually sufficient.

Mechanical vignetting occurs when light beams are partially blocked by external objects such as thick or stacked filters, secondary lenses, and improper lens hoods.

Natural vignetting (also known as natural illumination falloff) is not due to the blocking of light rays. The falloff is approximated by the "cosine fourth" law of illumination falloff. Wide-angle rangefinder designs are particularly prone to natural vignetting. Stopping down the lens cannot cure it.

Flare

Bright shapes or lack of contrast caused when light is scattered by the surface of the lens or reflected off the interior surfaces of the lens barrel. This is most often seen when the lens is pointed toward the sun or another bright light source. Flare can be minimized by using anti-reflection coatings, light baffles, or a lens hood.

Ghosting

Glowing patches of light that appear in a photograph due to lens flare.

Retrofocus design

Design with negative lens group(s) positioned in front of the diaphragm and positive lens group(s) positioned at the rear of the diaphragm. This provides a short focal length with a long back focus or lens-to-film distance, allowing for movement of the reflex mirror in SLR cameras. Sometimes called an inverted telephoto lens.

Anastigmat

A photographic lens completely corrected for the three main optical aberrations: spherical aberration, coma, and astigmatism.

By the mid-20th century, the vast majority of lenses were close to being anastigmatic, so most manufacturers stopped including this characteristic in lens names and/or descriptions and focused on advertising other features (anti-reflection coating, for example).

Rectilinear design

Design that does not introduce significant distortion, especially ultra-wide angle lenses that preserve straight lines and do not curve them (unlike a fisheye lens, for instance).

Focus shift

A change in the position of the plane of optimal focus, generally due to a change in focal length when using a zoom lens, and in some lenses, with a change in aperture.

Transmittance

The amount of light that passes through a lens without being either absorbed by the glass or being reflected by glass/air surfaces.

Modulation Transfer Function (MTF)

When optical designers attempt to compare the performance of optical systems, a commonly used measure is the modulation transfer function (MTF).

The components of MTF are:

The MTF of a lens is a measurement of its ability to transfer contrast at a particular resolution from the object to the image. In other words, MTF is a way to incorporate resolution and contrast into a single specification.

Knowing the MTF curves of each photographic lens and camera sensor within a system allows a designer to make the appropriate selection when optimizing for a particular resolution.

Veiling glare

Lens flare that causes loss of contrast over part or all of the image.

Anti-reflection coating

When light enters or exits an uncoated lens approximately 5% of the light is reflected back at each lens-air boundary due to the difference in refractive index. This reflected light causes flare and ghosting, which results in deterioration of image quality. To counter this, a vapor-deposited coating that reduces light reflection is applied to the lens surface. Early coatings consisted of a single thin film with the correct refractive index differences to cancel out reflections. Multi-layer coatings, introduced in the early 1970s, are made up of several such films.

Benefits of anti-reflection coating:

Circular fisheye

Produces a 180° angle of view in all directions (horizontal, vertical and diagonal).

The image circle of the lens is inscribed in the image frame.

Diagonal (full-frame) fisheye

Covers the entire image frame. For this reason diagonal fisheye lenses are often called full-frame fisheyes.

Extension ring

Extension rings can be used singly or in combination to vary the reproduction ratio of lenses. They are mounted between the camera body and the lens. As a rule, the effect becomes stronger the shorter the focal length of the lens in use, and the longer the focal length of the extension ring.

View camera

A large-format camera with a ground-glass viewfinder at the image plane for viewing and focusing. The photographer must stick his head under a cloth hood in order to see the image projected on the ground glass. Because of their 4x5-inch (or larger) negatives, these cameras can produce extremely high-quality results. View cameras also usually support movements.

135 cartridge-loaded film

43.27 24 36
  • Introduced: 1934
  • Frame size: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm
  • Area: 864mm2
  • Double perforated
  • 8 perforations per frame

120 roll film

71.22 44 56
  • Introduced: 1901
  • Frame size: 56 × 44mm
  • Aspect ratio: 11:14
  • Diagonal: 71.22mm
  • Area: 2464mm2
  • Unperforated

120 roll film

79.2 56 56
  • Introduced: 1901
  • Frame size: 56 × 56mm
  • Aspect ratio: 1:1
  • Diagonal: 79.2mm
  • Area: 3136mm2
  • Unperforated

120 roll film

89.64 56 70
  • Introduced: 1901
  • Frame size: 70 × 56mm
  • Aspect ratio: 5:4
  • Diagonal: 89.64mm
  • Area: 3920mm2
  • Unperforated

220 roll film

71.22 44 56
  • Introduced: 1965
  • Frame size: 56 × 44mm
  • Aspect ratio: 11:14
  • Diagonal: 71.22mm
  • Area: 2464mm2
  • Unperforated
  • Double the length of 120 roll film

220 roll film

79.2 56 56
  • Introduced: 1965
  • Frame size: 56 × 56mm
  • Aspect ratio: 1:1
  • Diagonal: 79.2mm
  • Area: 3136mm2
  • Unperforated
  • Double the length of 120 roll film

220 roll film

89.64 56 70
  • Introduced: 1965
  • Frame size: 70 × 56mm
  • Aspect ratio: 5:4
  • Diagonal: 89.64mm
  • Area: 3920mm2
  • Unperforated
  • Double the length of 120 roll film

Shutter speed ring with "F" setting

The "F" setting disengages the leaf shutter and is set when using only the focal plane shutter in the camera body.

Catch for disengaging cross-coupling

The shutter and diaphragm settings are cross-coupled so that the diaphragm opens to a corresponding degree when faster shutter speeds are selected. The cross-coupling can be disengaged at the press of a catch.

Cross-coupling button

With the cross-coupling button depressed speed/aperture combinations can be altered without changing the Exposure Value setting.

M & X sync

The shutter is fully synchronized for M- and X-settings so that you can work with flash at all shutter speeds.

In M-sync, the shutter closes the flash-firing circuit slightly before it is fully open to catch the flash at maximum intensity. The M-setting is used for Class M flash bulbs.

In X-sync, the flash takes place when the shutter is fully opened. The X-setting is used for electronic flash.

X sync

The shutter is fully synchronized for X-setting so that you can work with flash at all shutter speeds.

In X-sync, the flash takes place when the shutter is fully opened. The X-setting is used for electronic flash.

Unable to follow the link

You are already on the page dedicated to this lens.

Cannot perform comparison

Cannot compare the lens to itself.

Image stabilizer

A technology used for reducing or even eliminating the effects of camera shake. Gyro sensors inside the lens detect camera shake and pass the data to a microcomputer. Then an image stabilization group of elements controlled by the microcomputer moves inside the lens and compensates camera shake in order to keep the image static on the imaging sensor or film.

The technology allows to increase the shutter speed by several stops and shoot handheld in such lighting conditions and at such focal lengths where without image stabilizer you have to use tripod, decrease the shutter speed and/or increase the ISO setting which can lead to blurry and noisy images.

Original name

Lens name as indicated on the lens barrel (usually on the front ring). With lenses from film era, may vary slightly from batch to batch.

Format

Format refers to the shape and size of film or image sensor.

35mm is the common name of the 36x24mm film format or image sensor format. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43mm. The name originates with the total width of the 135 film which was the primary medium of the format prior to the invention of the full frame digital SLR. Historically the 35mm format was sometimes called small format to distinguish it from the medium and large formats.

APS-C is an image sensor format approximately equivalent in size to the film negatives of 25.1x16.7mm with an aspect ratio of 3:2.

Medium format is a film format or image sensor format larger than 36x24mm (35mm) but smaller than 4x5in (large format).

Angle of view

Angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

As the focal length changes, the angle of view also changes. The shorter the focal length (eg 18mm), the wider the angle of view. Conversely, the longer the focal length (eg 55mm), the smaller the angle of view.

A camera's angle of view depends not only on the lens, but also on the sensor. Imaging sensors are sometimes smaller than 35mm film frame, and this causes the lens to have a narrower angle of view than with 35mm film, by a certain factor for each sensor (called the crop factor).

This website does not use the angles of view provided by lens manufacturers, but calculates them automatically by the following formula: 114.6 * arctan (21.622 / CF * FL),

where:

CF – crop-factor of a sensor,
FL – focal length of a lens.

Mount

A lens mount is an interface — mechanical and often also electrical — between a camera body and a lens.

A lens mount may be a screw-threaded type, a bayonet-type, or a breech-lock type. Modern camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body, unlike screw-threaded mounts.

Lens mounts of competing manufacturers (Canon, Leica, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance (distance from the mechanical rear end surface of the lens mount to the focal plane) is also different.

Lens construction

Lens construction – a specific arrangement of elements and groups that make up the optical design, including type and size of elements, type of used materials etc.

Element - an individual piece of glass which makes up one component of a photographic lens. Photographic lenses are nearly always built up of multiple such elements.

Group – a cemented together pieces of glass which form a single unit or an individual piece of glass. The advantage is that there is no glass-air surfaces between cemented together pieces of glass, which reduces reflections.

Focal length

The focal length is the factor that determines the size of the image reproduced on the focal plane, picture angle which covers the area of the subject to be photographed, depth of field, etc.

Speed

The largest opening or stop at which a lens can be used is referred to as the speed of the lens. The larger the maximum aperture is, the faster the lens is considered to be. Lenses that offer a large maximum aperture are commonly referred to as fast lenses, and lenses with smaller maximum aperture are regarded as slow.

In low-light situations, having a wider maximum aperture means that you can shoot at a faster shutter speed or work at a lower ISO, or both.

Closest focusing distance

The minimum distance from the focal plane (film or sensor) to the subject where the lens is still able to focus.

Closest working distance

The distance from the front edge of the lens to the subject at the maximum magnification.

Magnification ratio

Determines how large the subject will appear in the final image. Magnification is expressed as a ratio. For example, a magnification ratio of 1:1 means that the image of the subject formed on the film or sensor will be the same size as the subject in real life. For this reason, a 1:1 ratio is often called "life-size".

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Electronic manual focus override is performed in the following way: half-press the shutter button, wait until the camera has finished the autofocusing and then focus manually without releasing the shutter button using the focusing ring.

Manual diaphragm

The diaphragm must be stopped down manually by rotating the detent aperture ring.

Preset diaphragm

The lens has two rings, one is for pre-setting, while the other is for normal diaphragm adjustment. The first ring must be set at the desired aperture, the second ring then should be fully opened for focusing, and turned back for stop down to the pre-set value.

Semi-automatic diaphragm

The lens features spring mechanism in the diaphragm, triggered by the shutter release, which stops down the diaphragm to the pre-set value. The spring needs to be reset manually after each exposure to re-open diaphragm to its maximum value.

Automatic diaphragm

The camera automatically closes the diaphragm down during the shutter operation. On completion of the exposure, the diaphragm re-opens to its maximum value.

Fixed diaphragm

The aperture setting is fixed at F/ on this lens, and cannot be adjusted.

Number of blades

As a general rule, the more blades that are used to create the aperture opening in the lens, the rounder the out-of-focus highlights will be.

Some lenses are designed with curved diaphragm blades, so the roundness of the aperture comes not from the number of blades, but from their shape. However, the fewer blades the diaphragm has, the more difficult it is to form a circle, regardless of rounded edges.

At maximum aperture, the opening will be circular regardless of the number of blades.

Weight

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

Maximum diameter x Length

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

For lenses with collapsible design, the length is indicated for the working (retracted) state.

Weather sealing

A rubber material which is inserted in between each externally exposed part (manual focus and zoom rings, buttons, switch panels etc.) to ensure it is properly sealed against dust and moisture.

Lenses that accept front mounted filters typically do not have gaskets behind the filter mount. It is recommended to use a filter for complete weather resistance when desired.

Fluorine coating

Helps keep lenses clean by reducing the possibility of dust and dirt adhering to the lens and by facilitating cleaning should the need arise. Applied to the outer surface of the front lens element over multi-coatings.

Filters

Lens filters are accessories that can protect lenses from dirt and damage, enhance colors, minimize glare and reflections, and add creative effects to images.

Lens hood

A lens hood or lens shade is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare. Flare occurs when stray light strikes the front element of a lens and then bounces around within the lens. This stray light often comes from very bright light sources, such as the sun, bright studio lights, or a bright white background.

The geometry of the lens hood can vary from a plain cylindrical or conical section to a more complex shape, sometimes called a petal, tulip, or flower hood. This allows the lens hood to block stray light with the higher portions of the lens hood, while allowing more light into the corners of the image through the lowered portions of the hood.

Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. In addition, lens hoods can offer some degree of physical protection for the lens due to the hood extending farther than the lens itself.

Teleconverters

Teleconverters increase the effective focal length of lenses. They also usually maintain the closest focusing distance of lenses, thus increasing the magnification significantly. A lens combined with a teleconverter is normally smaller, lighter and cheaper than a "direct" telephoto lens of the same focal length and speed.

Teleconverters are a convenient way of enhancing telephoto capability, but it comes at a cost − reduced maximum aperture. Also, since teleconverters magnify every detail in the image, they logically also magnify residual aberrations of the lens.

Lens caps

Scratched lens surfaces can spoil the definition and contrast of even the finest lenses. Lens covers are the best and most inexpensive protection available against dust, moisture and abrasion. Safeguard lens elements - both front and rear - whenever the lens is not in use.