A Teleconverter Quick Assessment

I'm not going to write this as a review or show you any photos, as I've not yet had enough experience in field shooting with the TC's and the 70-200mm f/2.8 lens. It seems we're headed into even more isolation with the pandemic surge going on, so that might not happen for awhile. I know a lot of you want my assessment on these two accessories this holiday season, so I'm going to provide a brief prose assessment based upon some short (closest focus to 10m) and long distance (50m) test shots only. I also haven't done much in the way of testing focus performance with the teleconverters, though at the moment I haven't seen anything that tells me that they impinge on the cameras' focus capabilities. I'll eventually get around to putting out a full review that discusses that as well as adding more information on optical performance. Until then...

TC-1.4X

Definitely the better of the two teleconverters on the 70-200mm f/2.8 S lens. Makes that lens basically a 98-280mm f/4 lens, which is close enough to a 100-300mm f/4 lens to fill in a key missing element in Nikon's Z lens lineup at the moment. 

Frankly, I've seen plenty of 100-300mm lenses that aren't as good as this combination. Wide open the results are very good in the center and maybe even very good in the corners. I do see a modest loss of sharpness as we move from the center out to the DX corner and then a gain back towards sharp as we move further to the corners. But that's minimal, and I don't think it changes my assessment any. 

The best this combo can do happens in the 70-135mm range one stop down (so about 100-200mm f/5.6). At those focal lengths and apertures, I'm not sure many could distinguish a difference from the native lens by itself, which is saying something pretty remarkable. 280mm f/5.6 is really quite good to the point where I have no issues at all with it, and f/4 is absolutely usable and most of you won't have any issues with that setting. 

The fact that a teleconverter doesn't increase the focus distance also makes this a darned good substitute for the missing telephoto macro lenses, though I'd generally recommend you stop down at least one stop if you're going to do that, as wide open at the very closest focus distance with the combo may be its weakest performance. 

Overall, a winner.

TC-2.0X

As far as 2x teleconverters go, this one is quite good, maybe even the best I've seen on a 70-200mm f/2.8. You get a 140-400mm f/5.6 out of the combination; once again a lens that doesn't exist in the Z system yet. 

The result is a bit like the F-mount 80-400mm: really good, maybe even exceptional, out to about 300mm, but with a clear softening from there to 400mm. So: wide open the results are very good in the center and out through to the corners at the short end, only good at the long end. Like the 1.4x, the best results are in the short half of the focal range one stop down, and also like the 1.4x the closest focus distance really requires stopping down to bring it fully into acuity. 

The combo is quite usable at 400mm f/5.6, but you're going to be bumping up your sharpening a bit to pull in a bit of well-controlled blur. 

Overall

I'd probably say "Recommended" for the 1.4x, and "Recommended (with limitations)" for the 2.0x, but again, this is an initial assessment on flat charts at short and very long distances. I need to see how the combinations perform with real subjects before making a commitment to that.

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