HiI’m on the fence of buying a lens with a little more reach. At first I was doubting to change systems (Sony 6xxx + 70-350 mainly due to the fast autofocus) and use it only for motorsport. But I’m not sure about it anymore since I’ve read some stuff about the Sigma 100-400mm. And besides that I really like my Z50.Can some people who own both lenses compare them? How is IQ between the two and won’t the Sigma lens be slower to autofocus?

I'm a huge fan of the 50-250DXVR and use it on Z50 and Z7II. I just don't consider it a great lens for sports. While my controlled tests with the 70-300E pushed me more towards the 50-250DXVR, overall I still get better sports results with the 70-300E. Maybe the size and larger VR mechanism are needed for stability and panning.In general, Nikon mirrorless AF-C depends heavily on more light and contrast. I notice much slower focusing when I stop down to f8/f11 with any lens.I don't think it would be fair to compare a 100-400 to the 50-250DXVR. The native mount, closer focusing, half the size, half the weight, half the cost; leads me to recommend getting both.Even if you prefer the 100-400, 70-300E, or another lens you'll want to keep the 50-250DXVR.It is now my primary lens on my Z50. (see my last note)I just spent some time with the R7 and RF100-400 and it was a lot of fun, but high ISO performance is lacking compared to Nikon. Maybe not after cleanup, but I'm after less workflow. So I stopped messing around, and got the 100-400S Z. I sold my 24-S, 85-S, and the 24-70F4S to fund it. I'll get more use out of the 100-400S. The two other lenses fill every other need I have; along with the two kit lenses.If they ever make the 40F2 in the SE build I'd get that too, but I'm sort of hoping for a 20F2 SE even if it was DX.My current bag: 14-30F4S, 24-120F4S, 100-400S, 16-50DXVR, 50-250DXVR, 24-50.NOTE: I'm also trying out the 15f1.4 Sony G (APS-C) with the megadap v2 this week. So far so good! It is about the same size as the 16-50DXVR extended. I can live with that for the f1.4, but it isn't cheap.

Thanks SkyrunrI'm not planning on selling the Z DX 50-250. Would keep that one to take with me when I'm going on a holiday. I've used the DX 50-250 extensively at some motorsport events and I can't complain of the results I'm getting. But sometimes I want a bit, a lot, more reach.So if the Sigma is at least as good as the DX (indeed more expensive, heavier, ....) I think I might order one and hope to use it on my next motorsport trip early September.

ANAYV is getting some nice bird photos with the Sigma 100-400.  I think the 300PF F4 is a viable option with a TC1.4 for motorsports too.  The speed could make up for the reach, with some cropping, and a good noise app.  I'm selling this lens too, and it will be the one I will miss the most.  I'm just done with the FTZ, and minimizing my bag.

I have the z50 kit with 16-50 and 50-250.Its a great combo but found I didn't have enough reach. started using the 70-300 p DX VR for birds for just that extra reach.Preordered a 100-400Z then won a sigma 100-400 for $450 on ebay.I was shocked that with moving subjects it acquires focus much better.Now it sits on my Z50, bought a bag with a side zip to store it with the ftz amazing.hummingbirds, dragonflies and eaglesAll heavily cropped.This is a 50-250 one Sigma 100-40 with TC1401 heavily cropped from this week.

Thanks Philblair for showing some pictures. Since AF is on par or even better, I think I will order one from the Sigma store on Amazon. In the EU they go for 750 new and about 700 second hand.

I really like the Sigma 100-400mm lens on my Z 50.AF seems almost as fast as on my Z 50-250mm lens.Few shots..BIF:Looking to try the 1.4x TC Sigma makes for this.Also tempted by Nikons  300mm PF lens..Not sure if the better optics allow for a bit more cropping.ANAYV

Thanks Anayv.