In preparation for a trip north to the Arctic that will include some wildlife photography of polar bears and other locals, I've been testing out some options for a relatively compact super-telephoto package that is also cost-effective (relatively speaking). I've reviewed the Sigma 150-600m Sports lens before and found it to be a good combination of portability and price while producing good image quality. Sure, there are definitely better super-telephotos, but the Sigma doesn't cost $16,000.
Over the years I've often been underwhelmed with teleconverters. But I was curious to see how Sigma's newest teleconverters worked with this lens. In their current range they offer two teleconverters, a TC-1401 that magnifies by 1.4x and a TC-2001 that magnifies by 2x. So I put them to the test. Here's what I found.
Size & Shape
As you can see, the TC-2001 is quite a bit deeper than the TC-1401. But the controls and exterior finish are otherwise identical.
I've been using these teleconverters on a Sigma 150-600mm Sports on a Nikon D810 full-frame camera. With the TC-1401, that brings the maximum focal length to about 850mm. With the TC-2001, it takes it up to a massive 1200mm.
Here are some practical examples of what that looks like.
Adding a teleconverter cuts down on the amount of light reaching the sensor and therefore reduces the working aperture range by about one to two stops. So they're not ideal when lighting conditions are challenging.
With the 150-600mm lenses zoomed to 600mm, the standard maximum aperture is f/6.3 (it's f/5 zoomed out to 150mm).
Adding the TC-1401 teleconverter makes the maximum aperture zoomed in fully now f/9.
Adding the TC-2001 teleconverter makes it f/13.
So with both you'll lose quite a bit of light.
When used with compatible lens and camera combinations, the TC-1401 mostly works with autofocus (so long as the camera is compatible with autofocus at f/8. On a Nikon D810 and 150-600mm Sports, I found it to be slower than the lens usually is, but still usable.
The TC-2001, though, is far more limited in its autofocus compatibility. The autofocus only works on the 120-300mm, and then only when the lens's firmware is up to date. If you're using it on the 150-600mm lenses, you'll have to use manual focus, regardless of whether your camera is Sigma, Nikon, or Canon. That's a major drawback. If you're shooting anything that's remotely moving, like sports or wildlife, it's going to make it close to unusable because the focus plain is so narrow at focal lengths of 1200mm. I found it hard enough even with still subjects.
You can find further details on the autofocus compatibility on Sigma's website.
Adding extra layers of glass will almost inevitably impact sharpness. But even factoring that in, I found the results to be very disappointing even with the TC-1401. Others haven't reported such a dropoff in sharpness; it's possible I had bad copies.
But I was underwhelmed by the sharpness. The resulting image is still very usable, but it's more than I'd like to see and enough to convince me not to use them.
It wasn't a shutter speed issue--these were at 1/2000 or faster when using the teleconverters. And they were on a tripod. I tried with and without OS (technically, OS should be off when using a tripod, but I wanted to rule out that potential issue).
Trying to correct it by using the USB dock to adjust the lens's backfocusing/forwardfocusing isn't an option, because that would then throw off the focus when using the lens without a teleconverter.
Rather than belaboring the point, here are some practical examples, using the same shot without the teleconverter as a reference. Roll over the images to get a full-size loupe view.
These teleconverters are only compatible with four lenses in Sigma's line: the 150-600mm F5-6.3 DG OS HSM | Sports, 150-600mm F5-6.3 DG OS HSM | Contemporary, and the 120-300mm F2.8 DG OS HSM | Sports, and the new 500mm F4 DG OS HSM | Sports.
I know others have reported using these successfully on other non-Sigma lenses, but I haven't tried that.
You can find more specifics on Sigma's website.
As you can tell, I've been generally underwhelmed by these teleconverters and have decided not to use either of them. My main complaint is on the issue of sharpness. But based on online customer reviews, not everyone has the same complaints, and some reviewers have praised their sharpness. Whether I got bad copies or I'm being especially pedantic, I don't know.
Find Them At
You can find them for the Sigma, Nikon, and Canon mounts at B&H Photo.