In this post, I’m going to compare performance in the image centre between these three telephoto lenses at 400mm:

• Nikkor Z 100-400 (e.g. from Amazon).
• AF-S Nikkor 80-400G (e.g. from Amazon).
• Sigma 150-600 Contemporary (e.g. from Amazon).

Unlike in the first post, where the focus was solely on the 100-400, I won’t provide exhaustive sample images of all apertures for all lenses – that would just be overwhelming. Instead, I’ll just provide the noteworthy cases.

30ft @ 400

The 150-600 is basically the same from wide open (f/6) through to f/8. It might be a tiny bit sharper at f/6 than narrower apertures.

The perceived sharpness of the 80-400 increases slightly when stopping down from wide open, and starts to soften again at f/7.1 and narrower. Its optimal aperture is f/6.3, vs f/5.6 for the 100-400.

Note that in practice I’ve tended to favour f/7.1 on the 80-400, including on 24 MP DX cameras which have higher pixel densities than the Z7 (and therefore should be more sensitive to diffraction, not less). That’s based on a large amount of real-world experience. There’s several possible explanations for the discrepancy, but my guess is that the increased depth of field, of f/7.1 over f/6.3, helps in practice because it:

• Increases the depth of field (sometimes important at close distances or with deep subjects).
• Provides a little more tolerance for focus errors.

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The 150-600 is clearly the sharpest, followed by the 80-400. The 100-400 is much softer than even the 80-400. The 80-400 is sharper at any aperture than the 100-400 is at any aperture (and the 150-600 exceeds both, similarly).

This was such a surprise that I went back and took many more photos with the 100-400, in a variety of modes (various autofocus modes, manual focus, VR on & off, silent shutter on & off), but the results were consistent – the 100-400 is much softer at 400 than its eight year old predecessor, let-alone the 150-600.

Note: the difference in sharpness is partially obscured by the JPEG compression used for the images in this post, even though I used the maximum possible JPEG quality. All my written statements throughout these tests are based on comparing the NEFs in Lightroom.

12ft @ 400

The 150-600 behaves the same as at 30ft – basically the same from f/6 (wide open) through f/8. Maybe a tiny bit sharper wide open.

The 80-400 gives its best performance at f/6.3 again. As at 30ft, the difference with f/5.6 (wide open) or f/7.1 is slight. f/8 is very slightly softer again, as diffraction more clearly kicks in.

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Unfortunately the comparison between the three is complicated by the fact that the 80-400 back-focused slightly while the 100-400 looks like it again front-focused a tad. After accounting for that it’s clear that the 80-400 is sharper than the 100-400. But the 150-600 is much sharper than either of them.

6ft @ 400

The 150-600 is out for this particular subject distance because it can’t focus this close.

The 80-400 is slightly sharper at f/7.1 than other apertures. Similar to the 100-400 (which still saw tiny improvement up to f/8, over f/7.1).

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At this point the comparison is getting tricky, because:

• The 80-400 back-focused again.
• The 100-400 is maintaining its nominal focal length much better than the 80-400. This change in focal length over different focus distances is typical behaviour for lenses – the stated focal length is usually only achieved at infinity; as you focus closer, their effective focal length drops.

It’s pretty close, between the two. There seems to be similar resolution on the image sensor, so the difference in subject detail is solely because of the difference in effective focal length. If you allow for that, then there’s a notable advantage to the 100-400.

MFD @ 400

Note here that the 100-400 can get down to about 3ft, while the 80-400 is not much shorter than the 6ft looked at above, and the 150-600 is way out at 10ft or so.

So unsurprisingly the 80-400 behaves the same as at 6ft – sharpest at f/7.1. Just like the 100-400. And the 150-600 is very similar from wide open (f/6) to f/8, with maybe a very slight improvement from stopping down just a tad, to f/6.3.

Note that I’ve also included the 150-600 at 600, in case you’re interested in comparing the maximum possible magnification across the three lenses.

Note: I don’t know why there’s such significant discrepancies in exposure, particularly with the 80-400. This was reproducible. The same exposure settings were used for all lenses. Possibly the differing fields of view impacted the camera’s metering?

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Here there’s no contest – the 100-400 is sharpest on the sensor (albeit by only a small margin over the 80-400), but also offers much higher magnification – almost twice what either of the other lenses are capable of. This matches the spec sheets – a maximum reproduction ratio of 0.38x for the 100-400 vs 0.2 for the 80-400 & 150-600.

The 150-600 is the worst by far, for sharpness on the sensor as well as magnification – not only do you have to zoom in to “600” to get similar magnification as the 80-400 does at “400”, but both are basically at something more like 200 if not less.

In fact to my eyes it appears that there’s nothing but empty magnification in going from 400 to 600 on the 150-600.

Conclusion

😧A surprise upset! I had assumed the 100-400 would be at least as sharp as the 80-400, and of course hoped it’d be even sharper. The 80-400 has always had good sharpness at 400 in my experience, so there wasn’t a lot of room for it to be surpassed. Still, that the 100-400 is much softer (at all but the very closest subject distances) is very disappointing.

The only thing the 100-400 has going for it (so far) is with very close subjects – there, the 100-400 is vastly superior, in large part because it can simply focus much closer while simultaneously retaining more of its nominal 400mm focal length. If you expect your subjects to always be less than ~10ft away, the 100-400 is clearly the better lens.

The 150-600 results surprised me, and may be tending unrepresentative, as they don’t match my real-world experience. I do think the 150-600 is a good lens – and excellent value at a quarter the price of either of the other two – but I’ve found it just doesn’t deliver results quite as good – nor as reliably – as the 80-400, except when you utilise its 50% extra reach. I strongly suspect this is mostly due to differences in image stabilisation – the 80-400 has the best image stabilisation of any lens I’ve ever used, while the 150-600’s image stabilisation is average at best.

Granted, this is only in the centre of the frame. Maybe the 100-400 has redeeming image qualities elsewhere in the frame? A subject for a subsequent post, perhaps.