Quote Originally Posted by falcon91 View Post
Hi,

Thanks for the responses.
I'm looking at these lenses for a couple of reasons.
Going to an f2.8 lens, if I understand correctly, should allow much faster autofocus which will help when shooting sports, particularly at nighttime under lights (Something that I've been doing for the last 6 months).
Also when taking portraits, it will help blur out the background significantly better than the 18-105.

Presently I've been shooting sports and pets/animals the best, so I thought having more control over depth of field and also improved autofocus speeds would be beneficial.

Thanks
Going to the Tamron 17-50 for sports loses you 55mm of focal length to make up for a stop of light or so. If you're fine shooting sports at 50mm (I'd suggest that it's too wide for sport, unless you're the referee on the field) then grab your 50mm 1.8 and shoot with that - it's already at the longest focal length of the Tamron and is 1 1/3 stops faster. When you need more focal length jump to your 70-300 and crank the ISO. The upgrades you can make for your sports shooting are a 70-200 f/2.8 or 70-200 f/4, however they seem a bit far off for the time being based on what you've said about your ability to shoot sport.

Moreover, not all f/2.8 lenses automatically focus faster - it's largely dependent on the lens. When people refer to a 'fast' lens, they're talking about the aperture and how much light is let in. Eg. f/2.8 is fast and your 50mm f/1.8 is faster.

If you're going to Tassie think about what you'll shoot - when I went last year I found myself shooting a lot of landscapes. Unfortunately at that stage it was on my iPhone (long story) but a wide-angle on my camera would have been great for what i was shooting. The Sigma 10-20 f/4-5.6 or Tokina 11-16 f/2.8 are good options and the Nikon 10-24 is of course excellent if you want to stay on brand. That range seems to be the only real gap in your collection.

You could maybe add the 85mm 1.8 later if you're into shooting portraits with nice bokeh (blurred background).

The 16-85 Nikon isn't really a huge upgrade from your current lens - it's very similar but only slightly better than the 18-105. The Tamron 17-50 will be a good walk-around lens for a long time to come, but it doesn't add any new capability to your kit.

As Ameerat said, think about what you can't do now that you'd like to do and go from there. Hopefully this is a bit of food for thought for you - I know how agonising lens choices can be!