At 28mm focal length all four lenses look very similar in the APS-C image-circle with a slight edge for the Sigma and Tamron in center sharpness. The Nikon has the best FF-corner. Above: Nikon Z 24-70mm f2.8 S on a Nikon Z7 at 50mm, f2.8; 100% crop from center, APS-C-corner, FF-corner; large original available at f2.8, f4.0, f5.6, f8.0, f11

So why would you buy the Leica 24-70mm f2.8 SL? You’re getting the best of many worlds. The autofocus is very reliable and useable for photojournalistic situations. The optics are great. And then there is the build quality. This is an incredibly well-balanced lens that isn’t front-heavy. Plus, it’s exceptionally weather-sealed. Build quality has become more and more of an issue for Gen Z and Millennials. Hopefully, the older generations who make the lenses and run the companies start to realize that. Three SLD (Special Low Dispersion) glass lens elements and four aspherical lens elements help minimize optical aberrations. To ensure outstanding image quality from the center to the edges of the photograph, the optical system minimizes coma, which causes points of light to streak, and transverse chromatic aberration, which cannot be corrected via aperture control, The optical system also minimizes distortion, which can be particularly evident in wide-angle shots, resulting in excellent optical performance throughout the zoom range. Lenses – The lens has dust inside that may affect images. The rubber zoom/focus ring is coming away from the barrel of the lens. Sigma has announced the newly developed 24-70mm F2.8 DG DN 'Art' for Sony E and Panasonic/Leica/Sigma L-mounts. The new lens joins the previously announced 14-24mm 2.8 DG DN Art as the second full-frame zoom in Sigma's DN (Digital Native) designed-for-mirrorless range.The four lenses look pretty similar in the center but at the APS-C-corner and the FF-corner the Sigma seems to have a slight advantage. Image quality is simply sumptuous. Sharpness and contrast are excellent throughout the entire zoom range, even at the widest aperture of f/2.8. The only noticeable dip in sharpness is at the extreme edges of the image frame, when shooting wide-open at 24mm. Ultimately, the Sigma is every bit as sharp as the Canon and Nikon own-brand lenses, and draws ahead of the Tamron at the long end of the zoom range. Catching a strong light-source shining directly into the lens is always a risky business: it could produce strange colorful ghost-images or reduce contrast considerably through flare and glare. The appearance of flare and ghosting depends on factors like the aperture and the angle of the light hitting the lens. To judge the proclivity of the new Sigma 24-70mm f2.8 DG DN Art for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting.

A 24-70mm lens is expected to have distortion – barrel at the wide end that transitions to pincushion at the long end. Size (diameter x length): 88 x 125mm (3.5 x 4.9in.) plus 36mm for the lens hood which is 106mm in diameter. Zooming in to 70mm extends the front-end of the lens (which is a single-barrel design) by another 34mm bringing the total length to 195mm (7.7in.). The Nikon is of similar size while the Sony is 11mm and the Panasonic 15mm longer (at 24mm focal length). The Tamron is the smallest lens at 73 x 118mm (2.9 x 4.6in.) plus 27mm for the lens hood. [+] The Tamron Lens hereby, is a mid-class Zoom, good, but no SP(Super Performance) Series. Tamron should make their SP 24-70/2.8 G2 (Canikon DSLR Lens) as SP recreation also for the current DSLM Generation as optical new calculation, just what Sigma did. At 50mm f2.8 the Sigma has a slightly fuzzy FF-corner and the Sony the softest APS-C-corner of the four lenses. Aspherical lenses necessitate refined expertise in the design and manufacturing of advanced, high-performance lenses.The new Sigma 24-70mm f2.8 DG DN Art produces a Bokeh that is less nervous than from the Tamron but not quite as soft as from the Sony or Nikon.

Aperture ring: No, just like the other lenses in this comparison, except for the Nikon which offers a multi-function control ring which can be assigned to operate the aperture or exposure compensation. [0] Had this lens four years now and got it to upgrade the superb DA SMC 18-55 3.5-4.5 that came with my now dead K100D. This was my first non kit walk around lens and it's attatched to the camera unless I need longer reach. It's what you expect from EX Glass, it's an absolute tank. HSM is snappy enough for my needs (Portrait and kids photography and some landscape. I've used it for astro and it's done the job nicely too) The only real downside is that it can be a touch soft at 2.8 to 3.5 but I've used it at 3.5 with good enough results on print up to 10x8s. It's bokeh could be better but I have realistically nothing to complain about. I was considering a 16-50 2.8 Pentax * but I decided against it because this came up used from a reputable dealer at a few hundred pounds sterling cheaper. If I didn't have this tomorrow I'd replace it in kind. I’m unsure how I feel about Leica using Sigma’s lens optics. I feel it creates too much clutter in the camera system and not enough innovation. Leica, however, has improved on what Sigma did in some ways.

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There are currently no full frame compatible zoom lenses available with apertures wider than f/2.8. The MF ring has about a 90 deg rotation; significantly more than the Tamron, and feels accurate and comfortable in manual mode. The focus ring also has no hard stop like the Tamron does. Sigma lenses are popular due to their ease of use, portability and the sharp results which they capture, with a variety of focal widths to choose from. These enable photographers to choose between wide aperture prime lenses for portraits, street and documentary, or versatile zooms which cover ultra wide, standard and telephoto focal widths. Slight improvement is seen in the periphery at f/5.6, but across the frame image quality is very good at f/4.