[stoppingdown]

So, the Sony 16-70 f/4 has been repaired and it come back worse than it was. The lab refuses other repairs saying it's within the specifications. I'm now going to replace it with a new lens.

Rumours about a new 16-70 lens from Sony haven't been confirmed, so the game is: Tamron 17-70 mm F/2.8 Di III-A VC RXD or Sigma 18-50mm F2.8 DC DN?

In short: Tamron is a more complete replacement of the focal range, but it's large and slow. More in detail my current evaluation is:

Reasons for Tamron 17-70 mm F/2.8 Di III-A VC RXD:

• Almost full replacement of focal range; I lose 16mm, but they are covered by the Sony 10-18m; in any case it covers 17-18mm, which Sigma doesn't; and while the 10-18mm covers the missing range, it's handy to have one mm more without the need of changing lens; on the long side, it covers the 50-70mm range, even though can be emulated with cropping without an excessive loss of quality;
  
• Stabilisation (maybe useless for the wide end, but not bad for the long one). I only have a single camera body with IBIS and it's the one being more frequently matched with macro or long tele lenses. OTOH since I'm now routinely using auto ISO, a safe shutter time is always used at the expense of higher ISO; but this is not a problem unless in some critical light conditions.
  
• If I'm not wrong, some reviews say this lens is sharper at corners in the wide end. Looking at the numbers in the OL reviews, tough, I have the impression that Tamron performance is more uniform from the center to borders, while the Sigma has a slightly better centre. Probably not much difference.
  

Reasons for Sigma 18-50mm F2.8 DC DN Contemporary Sony E:

• Cheaper (489-505€ vs 597-619€), but 130€ don't make a big difference;
  
• Lighter (290g vs 525g) and smaller (75mm vs 119mm in length); the size difference is really tempting me.
  
• Substantially better flare, especially at long end. I value this feature because it's not unlikely that I have the sun in the frame.
  
• Better built, even though this is a less relevant point for me.
  
• Better quality of bokeh, considering that both lenses are obviously mediocre in this aspect. Not really important for a landscape lens, but I've occasionally used the 16-70mm for plants.
  
• It has a specific lens profile in C1 (no profile for the Tamron).
  

While many points are subjective, an objective one that I'd like to clarify is about sharpness: is it my last point about Tamron correct?

Thanks.

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Just to have an idea of sizes, here are the two lenses compared with the Sony 16-70mm ƒ/4 and the Sigma 105mm ƒ/2.8.

https://camerasize.com/compact/#831.938,...5.445,ha,t

[Klaus]

Yes, these are very different lenses indeed. PERSONALLY, I enjoyed the Sigma more than the Tamron ... but then you know me by now ;-)

[stoppingdown]

At the moment it's my feeling too. What do you think about their sharpness compared?

[Klaus]

I reckon the Tammy may be a bit better in the overlapping range.

[stoppingdown]

It's probably my toughest buy decision so far. Shouldn't had been a troubled year I'd probably order both (plus a new SEL1670Z out of curiosity, to check whether something has changed with recent copies) and try all of them for a few weeks; then return two of them.
I decided to proceed in the following way: ordered the Sigma and I'll use it for some time. Let's see in the field how I do without the 16-18 range. In case of problems I'll sell it, to try the other.

[stoppingdown]

Yesterday I ordered the Sigma and now it's here (superfast deliivery). I perfectly understand why Klaus like it: for the price, it's beautifully made. I ran a first quick test: no decentering detected (AMEN!). It seems to be a tad sharper than the SEL1670 at the center (obviously there's no reason in comparing the borders of the degrated repaired copy; I'll later try to understand if some kind of comparison can be done with the old tests done when the Sony lens was not broken, even though they were performed at 16MP). At 35mm it seems to be even as sharp (or just a tad less sharp) than my current 35mm prime. BTW, I ran the test at ƒ/8, which seems not to be the sweet spot of this lens.
Shooting at 50mm and cropping to a 70mm equivalent seems to be only a tad less sharp than the SEL1670 at 70mm, so the long range — as supposed — won't be a problem.
Now I'll try it for a few time to see whether the 16-18mm missing range is a problem for me. BTW, in my previous evaluation I missed the fact that since a few years it's very easy to stitch panoramas (it had been always possible, but ten years ago this capability wasn't embedded in Lightroom/Capture One, and I'm lazy) — so in the end I suppose this lens will do good.

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I forgot: given that this lens is as sharp or even sharper at ƒ/5.6 and ƒ/4, unless hyperfocal is required this means that you gain two stops of stability, partially compensating the lack of OSS.

[stoppingdown]

When you follow the 2/3 top lens reviewers on the web (OL at the first place) you seldom have surprises when you buy a lens. The Sigma lens is confirming the many good features and the few pitfalls. Very sharp for landscape; good flare management with the sun in the frame through the whole focal range (much better than the Sony SEL1670Z that was a sort of Russian roulette, often producing purple/green streaks that seemed to be due to sand scratching the glass); very poor performance in close up at tele focal length and full open because a drop of contrast, but above all a monster LoCA; good performance and bokeh when stopped down to ƒ/5.6 - 8 (the Sony lens has about one stop of advantage here); good performance in close up at wide focal length even full open. So, yes, in some circumstances it enables you to take a decent flower/critter photo when you don't have a true macro length at hand.

[Rover]

I would say Tamron on the face of it, but it depends on what other lenses (if any) you'll be using alongside the one you choose. If it's a part of the 3-zoom kit with an UWA and a telezoom, then I guess the shorter range of the Sigma might not mean very much in practice.

[Klaus]

The Tamron is very good, but it's a conceptual oddball. It's a huge (long) lens for what it is. On small mirrorless cameras, it feels misplaced.
The Zeiss 16-70mm f/4 or the Fuj 16-80mm f/4 have just the right mixture if they weren't such flawed performers.
I hope that Sigma will come out with something decent along these lines eventually.

[toni-a]

In APS-C world Canon EFS is absolutely underrated IMHO.
I am still using it and very happy with the results, I still love my 15-85 who never let me down, despite being released as early as 2009, Sony APS-C has very good camera bodies but when it comes to lenses, it's a totally different story, despite being an open system...