Understanding and Using Teleconverters

We've all been there before. You're trying to frame a subject, a bird soaring or a distant athlete, and your lens just doesn't have enough reach. It's time to invest in a more expensive, ultra-telephoto zoom lens. Or is it? There's another option, a hidden gem in the photographer's toolkit: the teleconverter. 

A teleconverter is used to extend the reach of the lenses you already own, but how exactly do they work, and is there anything else you need to know before clearing space in your kit for a teleconverter? Let's see what we can find out.

Right about now, you're probably wondering exactly how teleconverters work. After all, telephoto lenses achieve their extra reach through specialised optical designs, with extra optical elements being put to work.

No, a teleconverter doesn't magically make these additional elements appear, but it instead uses its own to magnify the central portion of your image, thus providing a tighter crop around your subject.

You still need to use a lens when working with a teleconverter, as it sits between your lens and camera body, and magnifies the image that your existing lens is sending to the sensor of your camera.

If you've done any prior research into teleconverters, you may be aware that they include figures such as 1.4x and 2x in their name. This is probably the easiest part to understand; this number refers to the amount of increased magnification the teleconverter supplies.

Putting this information to use in a hypothetical situation; attaching a 1.4x teleconverter to a 300mm telephoto prime lens increases its focal length to 420mm, while using the same lens with a 2x teleconverter increases the focal length to a huge 600mm.

You can't expect to be gifted all of this additional magnification for free; there's always a trade-off! With teleconverters, the main catch is that it makes your lens a little slower, in terms of its maximum aperture rating, usually by 1 or 2 stops depending on the magnification of the teleconverter. 

Understanding how teleconverters affect aperture is made easier by putting this into a real-life example. If your lens's maximum aperture is f2.8, this would be lowered to f4 or f5.6 depending on the teleconverter used.

Teleconverters also often have other drawbacks, such as slowing down autofocus speeds of the lens, and reducing image quality due to magnifying any aberrations captured, although it must be said that thanks to many advancements in technology, manufacturers do an excellent job at reducing these issues in modern models.

It’s also worth mentioning that teleconverters are unfortunately quite limited in terms of lens compatibility. There are specific camera lenses that a teleconverter will work with in harmony, which are generally lenses with a fast aperture rating; this is due to these lenses being able to handle the inevitable loss of light and still function satisfactorily. Before making the plunge on a teleconverter, make sure you confirm compatibility with your camera gear.

It seems obvious that a teleconverter is used by anyone wanting to increase their magnification, to bring distant objects closer, which makes them particularly popular with anyone who is developing an interest in wildlife or sports photography, but there are also other benefits that you may not have considered. A teleconverter is way lighter than a lens with the same magnification, making it perfect for photographers who are on the move and carrying their gear on foot.

Also when compared to a lens with similar magnification, a teleconverter works out to be much more affordable. When you have finished using it, it can quickly be removed from your camera, leaving you to work with your original focal length, which adds undeniable versatility to your kit.

Now's a good time to summarise everything that we have learnt with a quick list of pros and cons.

Pros of using a teleconverter:

• Increased magnification
• Smaller and lighter than telephoto lens gear
• More affordable
• Easy to use
• Quick & easy to install and remove

Cons of using a teleconverter:

• Results in light loss, which directly affects aperture
• Can reduce image quality
• Slower AF performance
• Only compatible with select lenses

If you are still unsure if a teleconverter is right for you, the expert staff at your local Ted’s store will be happy to discuss your options with you. Whether you ultimately decide on a teleconverter or a longer lens, our photography blog is here with hints and tips, so you can get the most out of your camera gear.