Buying a pair of lens

FACTORS TO CONSIDER WHEN BUYING A CAMERA LENS

Buying a good lens is one of the biggest concerns of camera owners. Which lens should I buy? Truth be told, lenses are expensive! The beauty of buying the right lens is that you can use it with multiple camera bodies making this a very prudent investment decision. It is also important to understand that you can spend thousands of dollars on a camera body, but if you match it with a lackluster lens, the quality of the pictures will not reflect the value of the camera. Prepare to spend more on lens if picture quality is your top priority.

Although a lens can give new lease of life to your camera as well as save on unnecessary spending buying a new one, buying a new pair of lens can often be quite confusing. However, it is an inevitable decision particularly in this era of interchangeable lens and the rapid development in camera technology.

Most manufacturers’ pamphlets that accompany the lens are normally a tabulation of numbers and letters that can be quite intimidating to many ordinary buyers of camera lenses. Fortunately, only a few of these details are important to new users and indeed to many non—technical users of lenses;

1. Focal Length– Focal length is the distance between the center of a lens and its focus (Read more on focal length). Focal lengths range can loosely be grouped as follows:

   Focal Length	Lens Type	Typical use
   8mm - 24mm	Ultra wide angle (fisheye)	Skyscapes, art
   24mm - 35mm	Wide angle	Interiors, architecture, landscapes
   35mm - 85mm (50mm common)	Standard	General purpose
   85mm - 135mm	Short telephoto	Portraits
   135mm - 300mm	Medium telephoto	Close sports, action
   300mm+	Super telephoto	Far sports, wildlife, nature, astronomy

2. Aperture (f-stop) – an opening through which light passes into a camera (Read more about aperture). On the body of the lens, you will see writings such as 1:2.8, f2.8, f/2.8 that represents the different formats that expresses aperture. The lower the aperture number, the higher the maximum aperture of a particular lens. A lens with a larger maximum aperture allows you to shoot in lower light without using flash and also gives a shallow depth of field, allowing the isolation of one element in a picture, an important aspect of creative photography.
3. Image Stabilization(IS) –Camera movements, whether from shaky hands or body movement, ruin your shots. The most basic method of countering this is a tripod but there are technologies that take it a step further, such as the IS. Image stabilization is a method of reducing blurring associated with motion of a camera to achieve sharper images and also allow the photographer to take shots at slow shutter speeds without necessary using a tripod. IS allows you the ability to capture sharp images of static subjects at slower speeds.Image stabilization is more important to cameras that have slow shutter speeds or long optical zoom lenses. When a lens is zoomed out to its maximum magnification, it becomes extremely sensitive to even the slightest motion.Optical image stabilization (using technology of the lens) is considered superior to digital image stabilization (using software technology), but it is more expensive.The rule of thumb for capturing sharp, handheld images is to hold a camera at shutter speeds slower than the equivalent focal length of the lens. E.g. a 50mm lens shouldn’t be handheld at speeds slower than 1/50-second, or a 30mm lens slower than 1/30-second. With IS, it becomes possible to capture sharp images of still objects with a 50mm lens at speeds down to 1/5-second.As you purchase your new pair of lens, ensure you look out for this critical setting particularly if motion of your camera will destroy your shots. Some manufacturers have put a brand name on their image stabilization technology. For example, Sony dubs it SteadyShot while Panasonic calls their Mega O.I.S and Pentax Shake Reduction but they perform the same function.

4. Format– Simply put, the lens format determines the angle of view of a particular lens when used with a particular sensor. Before explaining the format in relation to lenses, a bit of history first. For a long time before digital cameras, 35mm film was a reference format due to its mass adoption and popularity. The standard size for film cameras was 135 films that measured 35mm in width including the perforations and left enough space for a 36x24mm negative size.The Field of View for any particular focal length lens is determined by the size of the film or sensor onto which the image circle is being projected. Therefore over time several focal length lenses became associated in photographers’ minds with a corresponding field of view for that focal length when used with a 35mm film camera. The 35 mm format, or simply 35 mm, thus became the standard name for the 36×24 mm film format or image sensor format used in photography or simply the ‘Full Frame Format’.

   All of the major manufacturers now make a range of lenses specifically optimized for APS-C cameras (Advanced Photo System type-C). Most SLRs and mirrorless cameras use APS-C sensors which are approximately 24mm x 16mm in size, or less than half the size of the 35mm film negative.  An APS-C size sensor gathers about 15 times more light (area) than a 1/2.5” sensor and 2.4 times less than full frame.Lenses designed for full frame will also work just fine on APS-C cameras. However APS-C lenses won’t work properly on full-frame cameras (E.g. for Canon lens, it’s physically impossible to attach an APS-C-optimized EF-S lens to a full-frame camera).

5. Crop Factor – When manufacturers started producing lenses with sensors smaller than 35mm, both the field of view and captured images appeared narrower, because the corners/edges of the image frame were getting chopped off (cropped). The 35mm lens sensor (full frame sensor) would project a circular image (the image circle), but the smaller lens sensor would only records a rectangular portion of the scene, throwing away the rest of the image.Crop factor is defined as the ratio of the dimensions of a camera’s imaging circle compared to a reference format (the 35mm film format). To mitigate the problem of cropping, most DSLRs and all compacts with smaller sensors ends up zooming in an image more than it would be on a full-frame sensor. Cropping makes a lens appear to have a longer focal length than it actually has. To obtain the effective focal length therefore, the real focal length is multiplied by the crop factor. Always check for the camera crop factor so that you can calculate the effective focal length.

6. Compatibility/Lens Mount: The first question you ask yourself when buying a new pair of lens is whether it will physically fit your camera. It’s futile to buy a new pair lens without ascertaining if it can physically fit your camera, as you may never use it. How a lens will be attached to the camera body is critical to the smooth operation of the package and also the quality of the output. While there are lens mount that can be used across brands, most manufacturers produces proprietary mounts. Always ensure this simple but critical aspect is checked before you even start bargaining the price. Most online stores such as Amazon have a link where you can test the compatibility of lens with the camera.
7. Special features: Most lenses will work in conjunction with camera-specific features to enhance their capacity and capability. However it is important to strike a balance as these features can significantly increase the price of the lens. Some of these features include;
   1. Autofocus: This feature is critical in some conditions. While manual focus may be necessary in some situations, autofocus is an added advantage where the target is moving and also if the photographer is not experienced enough. If there are any special features you require, such as silent autofocus, then list these too. Lenses without a silent focus tend to be noisy during operation and may scare a subject.
   2. If you plan to shoot video with your camera, choose a lens with video-specific autofocus. The continuous autofocus keeps your subject clearly in focus even while panning, zooming and shooting subjects in action.
   3. Manual focus override: Almost all lenses include a manual-focusing ring, which allows you to manually adjust the focus instead of relying on autofocus. When precise focusing is critical to the result such as when the depth of field is very small or where the focus point is featureless, many photographers worry about the intermittent uncertain nature of auto-focus. Some lenses have a manual focus override that allows the adjustment of the portion of the scene in focus manually without first switching out of autofocus mode for more precise control. A useful technique is to let the auto-focus make the first selection and then to use the manual focus override to fine-tune the focus.
      

      This Canon EF 24-105mm f/4L IS USM Zoom Lens aspherical optical image stabilization function with ultrasonic focus motor manual override (AF/MF buttons).

There are a few other aspects of build and operation that you may wish to consider when buying a lens.

1. Intended use: Many a times, it may not be practical to buy a lens for all occasions. Often one-fit-all lens may be hard to come by which demand several different lenses to cover all you needs. For example, the intended use will define the shutter speed (and thus f-stop number). If you are taking photos where the target is moving, a lens with f-2.8 or lower will be desirable. However, aperture also controls depth of field so the smaller the f-stop number the less depth of field. So the onus is on you to balance between your competing requirements so that you get a compromise and intended result.
2. Lighting conditions: Light is the foundation of photography. Photography is all about light. The camera cannot record images unless there is some sort of light to illuminate a scene or target. That fact stands true whether you are taking pictures in natural light, candlelight, or artificial light.Light conditions govern critical settings of the lens such as f-stop. For example, at least f-2.8 lens would be suitable for well-lit indoor while at least f-1.8 lens would be more appropriate for darker interiors. Would a better lens alleviate the blur in low light? This is a common question with buyers of lens. While a straight answer of ‘Yes’ will suffice, the truth is that even a faster, more expensive lens, will give you undesired results with the wrong settings.A camera can automatically set the exposure in any conditions, even indoors or at night by adjusting the lens aperture and using slower shutter speeds so that the sensor is exposed for longer. However this will only apply up to a certain point upon which blurring will creep in. At this stage, a lens with the image stabilisation function will certainly help, but again only up to a point when you require the camera’s ISO setting.

3. Size & Weight – The size and weight of the lens should be secondary to other priority factors such as the intended use and conditions of use. Lens features such as focal length and aperture have a bearing on the size and the weight of a lens. This is mainly because they dictate the complexity and the quantity of glasses to be used and internal construction of the lens. The most important consideration is the usage of the lens and mobility. If for example you intent to shoot hand-held, then it is obvious that a lighter lens will be the obvious choice. Where heavier lenses are necessary, then a tripod should be engaged to support the lens.