Sigma 18-300mm F3.5-F6.3 Contemporary

Conclusion

The Sigma 18-300mm F3.5-6.3 DC Macro HSM F3.5-6.3 "Contemporary" is an interesting lens, to say the least. While it does not deliver the stellar optical performances of, say, a Limited-series prime lens, it offers something not many lenses can boast: unmatched versatility.

The 18-300mm has a lot going on for it: a 16.7x zoom range, a compact and light form factor, modern, silent AF and good manufacturing tolerances. The elephant in the room is the zoom range: near class-leading (the Tamron 16-300mm has that claim but is only available in non-Pentax mounts), this range means that in many circumstances the 18-300mm is all you need when leaving home.

Of course, focal length is not everything, and the Sigma 18-300mm comes with many compromises. One is the maximum aperture. While reasonably fast wide open, at F3.5, it quickly drops and ends up at a slow F6.3 at 300mm. This slow aperture is unavoidable given the lens' size, and decreases the usefulness of the lens in low light.

Another compromise is the resolution, or sharpness. In general, the lens performs well in the center of the frame. Sadly, the same cannot be said of the edges and corners, where the lens often is quite soft. Again, this is not a surprise, but something to bear in mind when using the 18-300mm.

Vignetting is one of the lens's strong suits. More visible wide open at 18mm, it quickly drops to levels that will not be bothersome. The slow apertures of the mid and tele ends are actually helpful here. Bokeh is also generally pleasing, especially at longer focal lengths. Distortion meets our expectations, being more visible at 18mm, but nothing unexpected.

Flare is a weak point of the lens. It shows in all our tested scenarios, and users should be aware of this. Chromatic aberration is not bothersome, but still present. Luckily it is easy to remove via post-processing.

Autofocus is good, but not great. The lens is hindered by its slow maximum aperture and can struggle in low light. When things become brighter, it reaches acceptable levels but is never a speed demon.

Ultimately, the question is: does the lens' versatility take precedence over the unavoidable compromises? One can get an optically superior lens for about the same price by looking at a Sigma 17-70mm, a Pentax DA 16-85mm, DA 18-135mm or D FA 28-105mm. None of these cover as broad a focal range as the Sigma 18-300mm, and for some this is reason enough to choose the latter.

The best answer might be given by the Sigma 18-300mm's many users, who seem to love the lens, and are able to create beautiful pictures with it.

Pros

• The ultimate versatile lens, extreme focal range in a small format
• 3-7 year warranty in key markets
• Good center sharpness
• Vignetting and distortion kept under control
• Good out-of-focus rendering
• Nice rendering, particularly in good light
• Silent AF

Cons

• CA and flare always present
• Soft corners in all conditions except 50mm
• AF can struggle in low light, especially at longer focal lengths
• Some cheap-looking materials (the lens is still well-assembled)

Pricing

The Sigma 18-300mm sells for $399 as of November 2018, which is well below the original launch price of $579.  Given that versatility that this lens offers, we believe that it is an excellent value.

In comparison, the Pentax 18-270mm costs $80 more, doesn't fare any better optically, and has a shorter warranty.

Rating

Who is it For

The Sigma 18-300mm is the ideal choice for anyone who hates switching lenses or carrying a lot of gear. Users willing to sacrifice some optical quality for convenience will be well served with this all-in-one lens. 

Please note that this lens is for APS-C cameras only and will not cover the full-frame image circle on cameras like the Pentax K-1.

The Bottom Line

A lens of compromise, balancing its qualities and flaws as well as can be expected, the Sigma 18-300mm will be a rewarding lens for those who understand, and work with, its limitations.  On the other hand, users interested in maximizing image quality while maintaining a moderately versatile zoom range would be better served by the Sigma 17-70mm or Pentax-DA 16-85mm

Be sure to check the user reviews or post your own if you already own this lens.