There’s a variety of add-ons you can buy to modify your lens’ behaviour or specification
There are many accessories that have been developed to alter the characteristics of your lens, typically to increase focal length or enable macro shooting, and as they’re available from several manufacturers the choice usually caters for all budgets.
So rather than having to invest in additional lenses, you can adapt an existing optic to mimic the characteristics of another lens. Not only is it a more affordable solution, but they will usually also weigh far less and be less of a burden to carry around.
Then there are filters and lens hoods, which largely don’t enable any particular effect but simply allow the photographer to control the light entering the lens. And should you ever feel limited by the lenses within your own system you can always use an adaptor to mount optics developed for others. When looked at as a whole, therefore, the lens accessory market is an exciting world of photographic possibilities; and, since many accessories can be used in combination with one another, what’s achievable is only limited by the user’s creativity.
Teleconverters sit between a camera body and lens, and their purpose is to increase the latter’s effective focal length. With an optical arrangement within their construction, they allow light which would otherwise exit the lens and come to focus on the sensor to continue travelling through the system, thus increasing the effective focal length of the set-up.
They are most commonly found in 1.4x and 2x varieties, figures which relate to their multiplication factor against a lens’s focal length. So, a 300mm f/2.8 lens used with the former will yield an effective focal length of 420mm, and with the latter will double the figure to 600mm. Other varieties such as 1.7x and 3x teleconverters also exist, although these are less popular options.
A 1.4x converter cuts down light transmission by one EV stop while a 2x converter cuts down two EV stops, so with the above lens this will impose respective limits of f/4 and f/5.6. Considering the shallow depth of field associated with longer focal lengths this reduction may not prove restrictive from a creative standpoint, although any increase in effective focal length also requires that shutter speed be raised to help keep the image sharp (which obviously becomes more difficult if the maximum aperture is made smaller).
Manufacturers often recommend that their own brand teleconverters be used with their lenses, while not all lenses are compatible with them — more affordable optics with slower maximum apertures tend not to be suited to use with a teleconverter as the maximum aperture would decrease so much that it’s not really usable. Check on your manufacturer’s website to see if your lens is compatible, while third-party options are also available.
Teleconverters can affect the optical quality of the lens, while the reduction in light can make it harder for AF systems to acquire focus. That said, they’re a much more affordable (and lightweight) alternative to investing in large expensive telephoto lenses.
Lens converters are an inexpensive way to change the focal length of a lens. They screw into the filter thread of an existing optic, and offer a fisheye, wideangle or telephoto view. As they can be mounted onto a variety of lenses they are classified by magnification factor rather than a focal length; this must be multiplied by your lens focal length to give the combined effective focal length. So, a 0.70x wideangle converter turns a 50mm optic into one with an effective 35mm length. Cheaper converters are likely to have poor control over chromatic aberrations and will almost certainly degrade image quality, but superior options from reputable brands such as Tiffen are also available.
Extension tubes and reversing rings
True macro lenses can be expensive, but a number of cheaper alternatives are also available, such as extension tubes. Unlike teleconverters, tubes have no glass elements, but simply extend the distance between lens and camera body. This means you can go past the minimum focusing distance determined by the lens, effectively magnifying your subject.
Because they contain no additional optics, tubes don’t affect the optical quality of a lens. They’re usually supplied as a set of three which can be used either on their own or in combination with one another, and those that have contacts provide support for both metering and autofocus, though for static subjects it may be easier to switch to manual focus for greater precision.
With some extension tubes, such as those with no electronic contacts, you may also need to meter differently from the way in which you are used to, as the connection between the camera and lens which ordinarily facilitates aperture control will be broken.
An alternative to extension tubes is reversing rings. These simply allow a lens to be reverse-mounted onto a camera, and with the contacts facing outwards the camera loses communication with the lens. This set-up has a fixed working distance, while lenses without aperture rings will also need to be used wide open. This all may sound like too much trouble, but this can easily and cheaply create a high-magnification set up, and with modern live view systems it shouldn’t be too difficult to judge correct exposure and focus either.
Filters are one of the most obvious lens accessories, and have been used for decades for tonal and colour control. The most common are ultraviolet (UV) filters, which many photographers keep permanently on their lenses for protection, and polarisers which are useful for darkening skies and minimising reflections. Neutral density (ND) filters, both graduated and non-graduated, are also widely used to control exposure. Many other types of filters exist, but the rise of digital photography has caused their popularity to drop. Polarisers and ND filters remain the only two filters whose effects are required while shooting, which explains why they have remained the most popular choices.
Perhaps the lens you wish to use isn’t available in your system’s mount, or you may have at some point switched systems without trading in all of your glass. Whatever the reason, the likelihood is that an adaptor exists for the task.
Manufacturers such as SRB-Griturn, Novoflex and Voigtlander all specialize in producing adaptors that can mount older optics from a variety of systems onto newer bodies, and a quick search online reveals an endless assortment of unbranded adaptors which can be picked up for next to nothing.
With no connection between the camera and lens, similar limitations occur as with extension tubes without contacts — namely that more automated control over aperture isn’t possible. Metering, therefore, must occur at the aperture you plan to use for your exposure. You may also need to adjust your camera’s settings so that it will work with unrecognised lenses, and as many older lenses predate autofocus they will also need to be manually focused.