I'm in the market for a full frame EF-mount standard zoom lens, so I've been doing a lot of research about different 24‑70mm f/2.8 and 24‑105mm f/4 options. I understand the tradeoffs in terms of focal length ranges and maximum apertures, and I already know that for my purposes, either type of lens would fit my needs pretty well.¹
What I'm having a hard time figuring out, and what is a high priority for me, is which option would give me the best image quality overall, given the same focal length and aperture. Specifically, the aspects of image quality that aren't as easy to address in post-processing. So sharpness, contrast, and color rendering straight from the lens are important. Things like peripheral shading and barrel/pincushion distortion can be fixed in post.
I've done a lot of searching to try to figure this out, but pretty much everything I've come across talks about one of two things:
- The focal length range and maximum aperture tradeoffs between a 24‑70mm f/2.8 lens and a 24‑105mm f/4 lens. I've already answered that for myself.
- Comparisons between different brands of lenses within the same class. These have helped, but haven't completely answered my question.
From everything I've learned, it seems that the Sigma 24‑70mm f/2.8 DG OS HSM Art and the Tamron 24‑70mm f/2.8 Di VC USD G2 are pretty much on par with each other, but the Canon EF 24‑70mm f/2.8L II USM is one of the best zoom lenses in the world, and is superior to both of the others. Unfortunately, the Canon is outside my budget, so it comes down to one of the third-party lenses if I go with a 24‑70.²
And it seems that the Sigma 24‑105mm f/4 DG OS HSM Art is a fantastic lens, highly recommended by pretty much everyone and seen as more or less equal to the Canon EF 24‑105mm f/4L IS II USM in every way except for zoom ring placement. The Sigma has the zoom ring out toward the front, which bothers a lot of reviewers. Zoom ring placement isn't such a big deal for me.
So the Sigma 24‑105 has great reviews, as does the Canon 24‑105, and they're comparable in price. Plus, the Sigma and Tamron 24‑70 lenses are seen as pretty okay, but not stellar. With all that in mind, it seems like one of the 24‑105 options would be best for me. But when I look at MTF charts and image quality comparisons at the same focal length and aperture, the Sigma 24‑70 seems to outperform either of the 24‑105s. That's got me a little confused.
Is this because people who've reviewed these lenses have higher expectations for a 24‑70mm f/2.8 lens than they do for a 24‑105mm f/4? Bottom line, I want to find the lens that, within my budget, will give me the best results overall, regardless of what family it's in.
¹My shooting consists of about 60% landscape, 25% still life, and the rest just general purpose usage. I shoot basically no sports, and not enough portraits to matter. So a wide aperture and dreamy, creamy bokeh are not high priorities for me, but sharpness and contrast are.
²Tokina also makes a 24‑70mm f/2.8, but I really don't like the Tokina focus clutch contraption.