When using an interchangeable lens camera like a DSLR or mirrorless system, understanding focal length is crucial for capturing impressive photos. The focal length influences the angle of view, focus area, and degree of background blur (bokeh). By learning how focal length works, you can choose lenses that allow you to frame your subjects exactly as you envision - adjusting the field of view, pinpointing the focus, and controlling background defocus. Mastering this fundamental lens characteristic opens up creative possibilities for gorgeous, impactful imagery with your camera system.
When light rays travel through a lens, they bend (refract) and converge at a specific point called the focal point. This is where the light focuses and forms an image. The focal length refers to the distance between the optical center of the lens and the image sensor. At this precise length from the lens, the sensor captures the focused image formed by the converging light rays.
Most camera lenses clearly display the focal length value. For example, in a lens labelled "28-75mm F/2.8", the "xx mm" part denotes the focal length range. There are two main types of lenses in this regard - prime lenses with a fixed focal length shown as a single number like "20mm", and zoom lenses which have a variable focal length range like "28-75mm". So if you see a focal length specified as a range of numbers, that indicates it's a zoom lens capable of varying its focal length. But if only one focal length number is listed, it's a prime lens with a single, fixed focal length.
Example of a zoom lens: 28-75mm F/2.8 Di III VXD G2 (Model A063)
Example of a prime lens: 20mm F/2.8 Di III OSD M1:2 (Model F050)
The key point about focal length is that it directly determines the angle of view captured by the lens. The angle of view refers to the width of the scene that the camera can capture through the lens - the larger the angle, the wider the field of view.
Lenses are broadly categorized into three types based on their angle of view: wide-angle, standard, and telephoto. A standard lens provides an angle of view similar to the human eye's natural field of vision. Wide-angle lenses offer an expansive wide angle of view, while telephoto lenses have a narrow, magnified angle ideal for distant subjects.
As a general guideline, focal lengths below 35mm are considered wide-angle, around 50mm is a standard lens, and above 75mm is telephoto.
Changing the focal length drastically alters the perspective and composition. For example, a portrait taken at 35mm with the TAMRON 35-150mm F/2-2.8 lens shows the subject in an environmental context with the background. But at 150mm, the longer telephoto focal length compresses the perspective, magnifying the subject's face while blurring the background for a shallow depth of field effect. This ability to creatively adjust the angle of view by varying the focal length of a zoom lens allows you to capture vastly different looks and impressions.
Another key attribute related to focal length is depth of field. Depth of field refers to the zone of acceptable sharpness in an image, extending from the focused subject to the background. A deep depth of field means that both the subject and background appear in focus over a wide range. Conversely, a shallow depth of field renders a blurred, smooth bokeh effect in the out-of-focus background areas surrounding the subject.
Lenses with shorter focal lengths and wider maximum apertures tend to produce greater depth of field. Wide-angle lenses are excellent digital photography lenses, where you want to capture both foreground and background elements in crisp focus. Their short focal length increases depth of field, allowing details throughout the scene to be rendered sharply.
On the flip side, telephoto lenses with longer focal lengths exhibit a very shallow depth of field. This results in pleasantly blurred bokeh backgrounds that make the main subject really stand out against the soft defocused areas. Leveraging this compressed look with pronounced bokeh is ideal for portraits and other scenes where you want to isolate the subject from the background.
While focal length is critically important, another key factor to consider when choosing a lens is the image sensor size of your camera body. Digital cameras primarily use two main sensor formats - 35mm full-frame and APS-C crop sensors.
A full-frame sensor measures 36mm x 24mm, which is the same size as 35mm film. This larger sensor captures a wider field of view, greater dynamic range, and lower noise compared to smaller sensors. The APS-C format has a smaller 23.5mm x 15.6mm* sensor size, resulting in a more tightly cropped angle of view.
Since lenses are designed for a specific sensor size, you'll need to select one that matches your camera's sensor format. Full-frame lenses can be used on APS-C bodies but provide a further crop. However, APS-C lenses cannot fully cover a full-frame sensor.
When using an APS-C sensor, you'll need to calculate the "35mm equivalent" focal length to understand the actual angle of view, as focal lengths are traditionally referenced to the full-frame format. This is done by multiplying the APS-C lens' focal length by the crop factor (around 1.5x for most brands).
For example, a APS-C lens at 20mm focal length has an equivalent full-frame angle of view of around 30mm (20 x 1.5). Consulting crop factor charts helps visualize the angles of view for different focal lengths on APS-C sensors when choosing lenses.
Category | 35mm full-frame | APS-C |
Wide | 24mm | 16mm |
Standard | 50mm | 33mm |
Telephoto | 180mm | 120mm |
Ultra-telephoto | 400mm | 266mm |
A lower f-number indicates a wider maximum aperture diameter, allowing more light to pass through the lens onto the sensor. This greater light gathering capability provides several advantages.
The maximum aperture f-number is calculated by dividing the focal length by the effective aperture diameter. So a lens with a lower maximum f-number like f/2.8 has a wider maximum aperture compared to one with a higher number like f/5.6.
Lenses with wider maximum apertures (smaller f-numbers) are more light-sensitive, enabling faster shutter speeds to freeze action and better low-light performance. They also provide a shallower depth of field for separating subjects with beautiful background blur.
So when evaluating lenses, consider both the focal length for your desired angle of view and perspective, as well as the maximum aperture f-number for its low-light capabilities and creative control over depth of field. Both specifications play vital roles in determining the lens' overall imaging performance.
Photographers should select Portrait lens based on their desired angle of view, subject magnification needs, and aperture requirements for different shooting scenarios like landscapes, portraits, sports, and wildlife.
Wide-angle lenses span from ultra-wide to standard focal lengths. The ultra-wide capability lets you get up close to large subjects like buildings while still capturing an immense view, resulting in dynamic, sweeping shots. The exaggerated perspective also enables unique portraits and pet photos that emphasize the subject's size and surroundings creatively.
11-20mm F/2.8 Di III-A RXD (Model B060) is the world's first compact, lightweight F2.8 ultra wide-angle zoom lens for e-mount Sony APS-C mirrorless cameras. Can be the Best Lenses for Filmmaking.
Learn MoreThe 17-28mm F/2.8 Di III RXD (Model A046) achieves a filter diameter of ø67mm, which is surprising for a large aperture ultra wide-angle zoom lens for full-frame cameras. It’s small and light weight with a good camera balance. It's a dedicated lens for mirrorless interchangeable -lens cameras that can be carried easily and can be used in various situations.
Learn MoreThe 17-50mm F/4 Di III VXD (Model A068)It's the world’s first lens covering from ultra wide-angle 17mm to the standard 50mm focal length. The highly-compact TAMRON 17-50mm F/4 Di III VXD (model a068) for Sony E-mount full-frame mirrorless cameras offers maximum versatility for still and video creators. From landscapes to living rooms, this lens captures all that you see.
Learn MoreA standard best zoom lens offers a versatile focal range spanning from wide-angle to telephoto perspectives around the 50mm mark. These flexible lenses excel not just for candids and portraits, but prove invaluable across a diverse array of shooting situations. At the wide end, they can capture expansive landscapes, while the telephoto capabilities allow zooming in on distant subjects like animals or architectural details. With this walkaround range, a quality standard zoom is an extremely versatile option capable of handling everything from environmental shots to telephoto compression effects in a single lens.
The 17-70mm F/2.8 Di III-A VC RXD (Model B070) is a large-aperture standard zoom lens for APS-C format mirrorless cameras. With a focal length range of 17mm to 70mm (a full-frame equivalent of 25.5-105mm) for daily use, this achieves a 4.1x zoom. The optical design ensures high resolution and high contrast not just in the center of the image but also in corners and at the edges. The quiet AF drive motor and the VC image stabilization mechanism facilitate hand-held shooting. In addition, by counteracting focus breathing, the 17-70mm F2.8 empowers users' expression of their creative intentions to the fullest degree. This highly practical lens allows you to easily enjoy the high image quality of a large F2.8 aperture for both still and video shooting.
Learn MoreThe 20-40mm F/2.8 Di III VXD (Model A062) is a new large-aperture standard zoom lens that thoroughly pursues portability. While covering the range from the ultra-wide angle of 20mm to the standard range of 40mm, it is the smallest and lightest in its class. It also offers high image quality throughout the entire zoom range, making it useful not only for still image shooting but also for video recording such as vlogging. The VXD, which is quiet and agile, achieves high-speed, high-precision autofocusing. It is a new, unprecedented large-aperture standard zoom lens that allows users to easily enjoy taking out and shooting both still and video.
Learn More28-75mm F/2.8 Di III VXD G2 (Model A063) is the second-generation fast-aperture standard zoom lens for Sony and Nikon full-frame mirrorless cameras, offering significantly improved optical and autofocus performance and new function customization. You can find 28-75mm complete review online.
Learn MoreTelephoto zoom lenses magnify distant subjects, making them the best lens for wildlife photography. Their long reach also flattens perspective when shooting landscapes during hiking trips. However, telephoto zooms also excel for portraits. Their shallower depth of field produces beautiful blurred backgrounds that isolate the subject with smooth bokeh. This compression effect renders flattering features and makes subjects pop against the defocused setting for striking portraits.
The 35-150mm F/2-2.8 Di III VXD (Model A058) is a high-resolution travel zoom lens that covers everything from the 35mm wide angle to the 150mm telephoto focal length, the first zoom lens achieving an aperture of F2 at the wide-angle end. It has a groundbreaking fast-aperture and utilizes the linear motor focus mechanism VXD (Voice-coil eXtreme-torque Drive), thereby achieving high speed, high precision autofocusing. The innovative lens design enabled us to greatly improve the lens's grip and functionality. The software, developed in-house, enables to easily customize functions and to update firmware.
Learn More70-180mm F/2.8 Di III VC VXD G2 (Model A065) has evolved to G2 level.This is the world’s smallest and lightest, fast-aperture telephoto zoom lens for Sony E-mount with astounding portability and superb image quality.
Learn MoreThe 70-300mm F/4.5-6.3 Di III RXD (Model A047) for full-frame Mirrorless lenses is a telephoto zoom lens designed and created so photographers of all skill levels can enjoy high quality images comfortably. The 70-300mm F4.5-6.3 covers a broad telephoto zoom range yet is the small and lightest weight. With special emphasis on resolving power, TAMRON has deployed special lens elements appropriately arranged to correct chromatic aberration, generally very strong in a telephoto lens, as well as other aberrations. Users can enjoy high-resolution images combined with stunning bokeh qualities that are achievable only with a telephoto lens. The lens also incorporates the RXD, a high-speed precision AF drive system that is remarkably quiet. The 70-300mm F4.5-6.3 is a versatile lens for photographing landscapes, sports and other action, pets, wildlife, and more. The lens also demonstrates its potential for portrait shooting, casual snapshots, and scenarios that require you to be mobile and shoot handheld, like sporting events.
Learn MoreUltra-telephoto zoom lenses provide an extreme magnification capability that allows you to enlarge and capture distant subjects that are impossible to get physically close to. This makes them perfectly suited for photographing wildlife from a safe distance, as well as action at large sporting venues, aircraft, trains and other far-away moving objects
The 50-400mm F/4.5-6.3 Di III VC VXD (Model A067) is an ultra-telephoto zoom lens with an 8x zoom starting at 50mm at the wide-angle end and compatible with full-frame mirrorless cameras. The lens delivers uncompromised high image quality over the entire 50-400mm focal length range, yet is as compact and lightweight as a 100-400mm class lens. Equipped with the VXD mechanism and the VC mechanism, the lens can quickly focus on the subject's movement when shooting sports and wild birds. The 50-400mm F4.5-6.3 is a new ultra-telephoto zoom lens that combines unparalleled image quality and mobility.
Learn MoreThe 150-500mm F/5-6.7 Di III VC VXD (Model A057) is compact enough to be handheld while maintaining a focal length of 500mm on the telephoto end. It allows users to easily enjoy the world of the 500mm ultra-telephoto lens while maintaining its high image quality. The high-speed, high-precision AF with excellent tracking performance and the VC mechanism support handheld shooting in the ultra-telephoto range.
Learn MoreFocal length refers to the distance between a lens's optical center and the camera's image sensor. This measurement critically dictates the angle of view captured. Lenses with shorter focal lengths are classified as wide-angle, providing an expansive field of view. Conversely, those with longer focal lengths are telephoto lenses, offering a narrower, magnified perspective. Standard lenses fall in between these two extremes. When selecting optics, carefully consider the focal length best suited to render your desired angle of view and framing for the subjects or scenes you aim to photograph.
The 35-150mm F/2-2.8 Di III VXD (Model A058) is a high-resolution travel zoom lens that covers everything from the 35mm wide angle to the 150mm telephoto focal length, the first zoom lens achieving an aperture of F2 at the wide-angle end. It has a groundbreaking fast-aperture and utilizes the linear motor focus mechanism VXD (Voice-coil eXtreme-torque Drive), thereby achieving high speed, high precision autofocusing. The innovative lens design enabled us to greatly improve the lens's grip and functionality. The software, developed in-house, enables to easily customize functions and to update firmware.
Learn MoreProduct Page | 11-20mm F/2.8 Di III-A RXD (Model B060) is the world's first compact, lightweight F2.8 ultra wide-angle zoom lens for Sony E-mount APS-C mirrorless cameras. Can be a great choice for video shooting.
Learn MoreThe 17-70mm F/2.8 Di III-A VC RXD (Model B070) is a large-aperture standard zoom lens for APS-C format mirrorless cameras. With a focal length range of 17mm to 70mm (a full-frame equivalent of 25.5-105mm) for daily use, this achieves a 4.1x zoom. The optical design ensures high resolution and high contrast not just in the center of the image but also in corners and at the edges. The quiet AF drive motor and the VC image stabilization mechanism facilitate hand-held shooting. In addition, by counteracting focus breathing, the 17-70mm F2.8 empowers users' expression of their creative intentions to the fullest degree. This highly practical lens allows you to easily enjoy the high image quality of a large F2.8 aperture for both still and video shooting.
Learn MoreThe 50-400mm F/4.5-6.3 Di III VC VXD (Model A067) is an ultra-telephoto zoom lens with an 8x zoom starting at 50mm at the wide-angle end and compatible with full-frame mirrorless cameras. The lens delivers uncompromised high image quality over the entire 50-400mm focal length range, yet is as compact and lightweight as a 100-400mm class lens. Equipped with the VXD mechanism and the VC mechanism, the lens can quickly focus on the subject's movement when shooting sports and wild birds. The 50-400mm F4.5-6.3 is a new ultra-telephoto zoom lens that combines unparalleled image quality and mobility.
Learn More