The new SIGMA 100-400mm F5-6.3 DG DN OS telephoto zoom, together with two teleconverters, offers 400mm, 560mm or 800mm capabilities in a relatively compact and light housing. The lens weighs 1,135g and is 197.2mm long at its furthest extension. It is Sigma’s fifth DG DN lens designed exclusively for full-frame mirrorless cameras.
At £899 (excluding the teleconverters) this “Contemporary” lens is a welcome addition to the ever-growing stable of L-Mount optics which can be used on Leica, Panasonic and Sigma cameras. It is based on the similar E-Mount lens with 22 elements in 16 groups (1 FLD and 4 SLDs) and 9 rounded diaphragm blades. Minimum focusing distance is 112 mm at the widest view, increasing to 160 mm at 400 mm. Maximum magnification ratio is 1:4.1 at 400 mm and the filter size is 67 mm.
The 1.4x TC1411 teleconverter increases the reach to 560 mm while narrowing the aperture range to f/7-9. Alternatively, the TC-2011 2x converter results in an 800 mm reach at an aperture range of f/10-12.6.
The x1.4 converter will cost £369.99 and the x2 version will be £399.99. I am trying to find out if these teleconverters will work with any other L-Mount lenses, especially the Leica APO VARIO-ELMARIT-SL
90–280 f/2.8–4.
x1.4 teleconverter 
x2 teleconverter
The SIGMA 100-400mm F5-6.3 DG DN OS features four-stop image stabilisation which works in conjunction with in-body stabilisation on suitable cameras. A dual-action zoom allows the lens to be extended either by using the zoom ring in the normal manner or by moving the extension in any out by hand.
Sigma’s announcement release expands on the capabilities of the new lens:
“State-of-the-art optical technology ensures very high-resolution results right to the edges of the frame, as well as high-contrast images throughout the entire focal range. A rounded diaphragm gives circular out-of-focus highlights, and Super Multi-Layer and Nano Porous coatings reduce flare and ghosting. The image quality rivals that of standard zoom lenses such as the SIGMA 24-70mm F2.8 DG DN | Art, ensuring a perfect match when used alongside these optics.
“The bokeh effects and compressed perspective achieved when shooting at these longer focal lengths will open up a range of new shooting possibilities, allowing a fresh approach to everyday scenes. The lens is perfect for wildlife, action and portraits, and thanks to its short minimum focusing distance, which gives a magnification ratio of 1:4.1, it’s also ideal for capturing close-up subjects in stunning detail.”
The SIGMA 100-400mm F5-6.3 DG DN OS will be available in UK retailers from 10 July 2020. You can find full details of the lens on Sigma’s web site here.