Clash of the APS-C Third-Party f/2.8 Standard Zooms: Sigma Versus Tamron

With modern zoom lenses for mirrorless cameras getting better and better each year, more people lean towards their utility, and this is especially common in all-purpose APS-C lenses like Sigma’s 18-50 f/2.8 and Tamron’s 17-70 f/2.8—but which of the two is better?

The Sigma 18-50mm f/2.8 DC DN Contemporary and Tamron 17-70mm f/2.8 Di III VXD are two popular lenses for APS-C mirrorless cameras, offering similar focal length ranges and constant f/2.8 apertures. However, they differ significantly in several key areas.

After spending a lot of time shooting with both on the Fujifilm X-System, I can say I know which of the two I prefer for most purposes, but I want to explain the differences before sharing my personal preference.

First off, price is a major factor. The Sigma 18-50mm is notably more affordable, often costing hundreds of dollars less than the Tamron 17-70mm. This price difference is primarily due to the Tamron's additional features, including a wider focal range and built-in image stabilization.

Image quality is another crucial consideration. Both lenses deliver impressive sharpness and detail, but the Tamron 17-70mm often edges out the Sigma 18-50mm, especially at the wide end of the zoom range. The Tamron's wider focal range offers more overall utility and even a shallower depth of field and higher optical compression due to that longer 70 mm reach.

Build quality is comparable between the two lenses. Both are well-constructed and feel robust, though the Tamron 17-70mm is significantly larger and heavier due to its additional features and longer zoom range.

Autofocus performance is excellent on both lenses, with the Tamron 17-70mm generally being slightly faster and more responsive. This can be particularly beneficial for capturing fast-moving subjects or in low-light conditions.

The Tamron 17-70mm incorporates built-in image stabilization (VC), which can be helpful for handheld shooting, especially in low-light conditions. The Sigma 18-50mm lacks this feature, relying on the camera's in-body image stabilization (IBIS) if available. On my Fuji X-T5 or X-S10, this is obviously not an issue, but it is something you should consider if your camera body has no in-built stabilization.

Both lenses produce very decent minimum focus distance numbers, with Sigma leading the way at 4.8 inches and Tamron at 7.5 inches, both of which are at the wide end of their range. Similarly, both lenses produce lovely, crisp sunstars, something I am a sucker for.

After all this Tamron glazing I have done, I am certain you will guess the 17-70 stays stuck to my camera most of the time, but you would be wrong. One significant advantage of the Sigma 18-50mm is its compact size and lightweight design. This makes it a more portable and convenient option for travel or everyday shooting. The Tamron 17-70mm, while still manageable, is noticeably larger and heavier.

It is my long-held opinion that the more convenient your camera system can be for you, the more you will keep it with you when out and about, and thus the more you will use it. This is certainly the case for me, and despite the many advantages the Tamron holds, it is the Sigma 18-50 f/2.8 that is a year-round attachment to my Fujifilm X-T5. When the two are married, the overall system becomes so compact that it is very easy to wear it around your neck, tuck it in a backpack, or stuff it in a glovebox (although I am more likely to let it roll around the floor of my car).

That being said, personal preference is such an important component of feeling good about your camera system, so it can be an extension of you.

Pros and Cons

While both lenses offer impressive performance, the choice between the Sigma 18-50mm and Tamron 17-70mm ultimately depends on your specific needs and priorities. If you prioritize affordability and a compact, lightweight lens, the Sigma 18-50mm is an excellent choice, though it suffers from a lack of optical stabilization and a more limited zoom range.

If you require a wider focal range, faster autofocus, image stabilization, and superior image quality, the Tamron 17-70mm is the better option, despite its higher price and larger size. The larger size is, to me, a buzzkill, leading to me carrying the camera less.