Do you need a teleconverter in 2025?

By Doug Gimesy | 5 March 2025

When a photographer wants to fill more of the frame with a subject, they normally have four choices; move themselves closer, reach for a telephoto lens, add a teleconverter, or crop in – either in post-production or using the camera’s crop mode.

However, moving closer isn’t always an option, and bigger telephotos lenses can be both expensive and heavy to carry. So, should you consider just adding a teleconverter to what you have, or just crop in later?

Teleconverters are just not for big prime lenses. They can be great to give just a little more reach for your zoom lenses as well. I’ll often use a 1.4x on a 70mm-200mm or 100-400mm to give me a 98-320mm or 140-560mm, like in this shot of a white-faced heron. Sony A1, FE 100-400mm F4.5-5.6 GM OSS + 1.4X Teleconverter @ 560mm. 1/1600s @ f10, ISO 500.

Talking teles

With today’s higher megapixel cameras, there are many times we can fill the frame by simply relying on the ability to crop in post.

At the same time, for those who don’t have a high megapixel camera (think 30MP+), thanks to programs like Topaz AI or Lightroom’s Super resolution, the potential for upscaling and then cropping offers pretty good results.

So, if cropping later can be such a good option, why even consider using a teleconverter at all? Let’s take a look.

As this black flying fox was still, I could slow down the shutter speed and get a low ISO. I knew the tight composition I wanted, so it made sense to get maximum pixels and detail of this magnificent animal. In this case, a tele was ideal to help realise the shot. Sony A1, FE 600mm F4 GM OSS + 1.4X Teleconverter. 1/800s @ f5.6, ISO 4000.

The positives

Using a teleconverter has a few benefits; both for how you plan to use the end image and for your creative choices.

The first is that a tele gives you a sharper image and more pixels straight out of the camera to print or crop from.

So, if you need the pixels, for say printing large for example, or the amount of cropping required is so great it impacts image quality, this is where teleconverters shine.

Whilst I could have easily cropped in to get the same composition of this pink-eared duck, given the good light conditions and still subject, I was able to still shoot at a low ISO. In turn, this gave me more pixels and hence greater detail for the final capture. Sony A1, FE 600mm F4 GM OSS + 1.4X Teleconverter. 1/640s @ f5.6, ISO 100. -1.7ev.

The other advantage to a teleconverter is a creative one in that it can give you a shallower depth of field at the same aperture. Let’s say you had a 400mm set at f/5.6. If you had a 200mm f/2.8 and added a 2x teleconverter, you’d get the same 400mm f/5.6 and with the compositional option of a shallower DOF/increase bokeh, versus cropping in on the 200mm.

The other advantage of course is that a teleconverter is typically small and can easily fit in a camera bag or pocket. They’re also much cheaper than upgrading to a new lens.

Wanting to ensure I didn't disturb this gannet feeding, keeping a good distance was paramount. So, with good light allowing a low ISO, and a relatively still subject making framing easy, I chose to use a teleconverter to 'get close'. Having decided this, the next key consideration was how to attach it without exposing my sensor to salty sea mist! Sony A1, FE 400mm F2.8 GM OSS + 1.4X Teleconverter. 1/2500s @ f4.5, ISO 400. +0.3ev.

So, what's a teleconverter?

A teleconverter (also sometimes called an ‘extender’), is a lens that fits between the camera body and a compatible primary lens increasing the primary lens’ focal length. Or to put it another way, it’s a magnifying glass that crops out the edge of a scene giving a narrower field of view and in doing so making the central area larger.

How much magnification they give depends upon the teleconverter, but most commonly you’ll find them as 1.4x or 2.0x.

So if you put a 1.4x on a 300mm f/4 lens for example, it will become a 420mm f/5.6 lens. If you put a 2x on a 70-200 f/2.8 it would become a 140mm-400mm f/5.6.

Also notice here how the f-stop has changed? A 1.4x teleconverter will add one stop to the lens, with a 2x adding two stops.

The negatives

With all of that, why wouldn’t you always choose to use a teleconverter than carry a potentially bigger and heavier lens?

Well, there are a few negatives, and these relate to the conditions you are shooting in and the subject you are photographing.

To me however, the greatest downside of a teleconverter is that you lose light to your sensor.

Depending on which type of teleconverter you are using, it will be one f-stop for a 1.4x and two f-stops for a 2.0x. It’s just the way f stops work. Basically, the f-stop number is the ratio of the focal length of the lens to the physical maximum diameter of that lens’ iris diaphragm (aperture), both in millimetres.

So, with a 200mm lens with a maximum aperture of 71mm, you would have a f/2.8 (i.e. 200/71) lens. Add a 2x teleconverter and the focal length increases to 400mm (which is what we want), but the physical diameter of the iris diaphragm doesn’t change. At 400mm, you now have a lens that’s 400mm/71mm, or an f-stop of /5.6. That’s just physics!

To this, as you are also adding another piece of glass, regardless of the f-stop, you will also lose some of the light transmission (which is called a T-stop, ‘T’ for transmission).

Cropping in-camera vs in post

For some reason, many people think that cropping in-camera is like adding a magical zoom capability to the system. I’ve even heard people say “I use a crop sensor to get closer”. The thing is, cropping in camera or using a cropped sensor just makes the image look like your lens has magical zoom capabilities because you are just seeing less of the scene. The end result is exactly the same as if you had cropped-in in post.

There is however a downside to this approach; you have thrown away parts of the scene and pixels that you might have been able to creatively include later. If there was one upside to cropping in camera, it’s only that you get smaller file sizes (and from this potentially faster shutter burst speeds and duration), but I think that’s a very small upside!

For teleconverters, this normally equates to about a quarter to half of a stop, so using one means that when you take an image (with the lens at its widest aperture), all else being equal, your ISO will need to be between 50% to 100% higher.

If you have lots of light and are already shooting at a low ISO, let’s say between 100-400, or your image is comprised of lots of midtones, whites and highlights, this likely won’t be an issue as you won’t notice the increased sensor noise.

But if you are already working in higher ISOs, say in the thousands, or you are taking images with lots of blacks and shadows (where noise really shows up), then doubling your ISO could become a problem.

One other image quality impact is that by adding an extra piece of glass, image quality can soften. With great teleconverters, especially 1.4x, I haven’t noticed a huge impact, but it is there.

Also, whilst not an image quality impact, something else to consider is that by adding a teleconverter, it may reduce a camera’s focus speed. This isn’t normally an issue when using expensive low f-stop prime lenses, but with other lenses (especially non-native glass) it’s worth considering.

Finally, as with any lens change, adding a teleconverter takes time, and depending on what you are trying to capture, the time you need to remove your lens, add the teleconverter, then add your lens back onto the teleconverter, steals time you could be shooting. Doing this in the field also means you are exposing the camera body to the risk of sensor dust.

This probably isn’t a dealbreaker of course, but it’s worth considering for locations where getting a sensor clean is not easy – i.e. day one of your three-week trip to Antarctica!

For action shots if using a fixed focal length lens, sometimes a teleconverter can be a disadvantage, as the subject can easily move out of frame, or suddenly get too close, and there is nothing you can do. This was the case in the first image using a 600mm with a 1.4 tele (i.e. 840mm); I just couldn’t centre it quickly enough. For the second image, the flying fox wasn’t moving as quickly, and I got lucky. But after that I decided to remove the tele and give more space to get it somewhere in the frame. Doing this also dropped my ISO and technically helped speed up my autofocus. The result was the third image, which I like, but also still had enough clean pixels to produce a large file crop.

So, what’s the best option?

Teleconverters are a great invention that allow photographers to shoot with a longer focal length and fill more of the frame, without having to buy or carry a longer lens.

They are also a relatively cheap investment, and they can usually be used on multiple lenses. But at the same time, the ease with which we can crop in post has never been better.

As a professional, if I need to fill more of the frame, can’t move, don’t have a bigger lens and ISO is not an issue, I will usually reach for one. It often gives me a slightly higher quality image with more pixels, and that’s important in my work.

But for the many photographers where lots of pixels aren’t important, and excluding the creative considerations a teleconverter may bring, I think the downsides of potential higher ISO noise, reduced focus speeds and other negatives mean you’re probably better to just focus on getting the shot at the time and cropping in later. ❂