Feldy

You already know the answer you just don't want to hear it. With the quality of lenses that you already own, the only lens for you is the Nikkor 200-400mm
Yes it is expensive but it will hold its value over the years if you ever want to part with it.
A word or warning. It took me testing 5 different lenses before I found one that was sharp all the way through. Several of them were soft around the 310-320 area

Feldy

You already know the answer you just dont want to hear it.
With the quality of the bodies and lenses you own the only answer is the 200-400mm zoom
Yes it is expensive but it will hold its value if you ever decide to part with it.
A word of warning. Make sure you test the lens you are going to buy. It took me 4 lenses before I found one that was
sharp all the way through. Several of them were soft around the 310-320mm range.
When you get the money buy a 70-200mm and then you'll have all the lenses you will ever need.

via the lens Loc: Northern California, near Yosemite NP

HI Homefree21,

I shoot Nikon and photo animals with long lenses. I bought the Tamron 150-600 (this is one version back) and had fairly good photos from it, although many people said it was soft at the end range. I found it to be acceptably sharp when my skills were working correctly. However, on one shoot last September the lens fogged up (it may have gotten slightly wet at the lens end as I almost fell into a river) and I could not use it on the shoot. I also had with me the Nikon 80-400 so I used that, with and without the TC. I liked the results with that lens and it was easy to hand-hold; the Tamron 150-600, while it can be hand-held, required more stablization for me. I then purchased the Nikon 200-500 and took that and the Tamron on a birding trip to New Mexico a couple of weeks ago. The Tamron, on the first day, lost its auto-focus and it could not be used at all. A couple of other people I talked to along the way at the birding refuge were also having problems with the Tamron autofocus system, even the current version. So, on that trip I used the Nikon 200-500 and I loved the results. Wonderful lens. Small drawback is that if the animal comes too close, you cannot shoot so I simply take a second camera ( I always do this anyway) and use that as needed, it had the 80-400 on it. Tamron did fix my lens, free (it said one fix was free) and it is laying on a counter in my office area not yet unwrapped: I do not feel that I can trust the lens. However, I always try to carry two long lenses when I go on an animal photo shoot so I got my photos. Have attached a photo of a flying crane taken with the Nikon 200-500.

speters Loc: Grangeville/Idaho

In the latest Popular Photography issue, the new Tamron actually came out on top, compared to the Sigma, not only optically, but it really shined with the implementation of the new image stabilization!

ggab Loc: ?

Coming to the party late, however.....
You mention you want to shoot wildlife including small animals, insects and landscape. I presume you are looking for the 150-600 lens for wildlife only.
I have the Tamron G1 series and have been very happy with it using it for the same purpose. Reading some reviews of the G2 vs Sigma vs G1 I conclude that the G2 and Sigma Contemporary do not bring enough to the table to justify the cost differential. Unless you are shooting exclusively on a tripod, Good Optical Stabilization is critical. The G2 has a few more switches, as does the Sigma, however in the 500mm range at roughly 1/125, the OS is better on the G1 than the G2.
I guess the primary question is, how much do you have to spend and are you getting paid for your pictures?
For me, the G1 was priced right and is serving very well. I really try not to get caught up on the esoteric part of this as I am not an esoteric photographer. Perhaps if I got paid and shot with a 50mp camera, things would be different.
Some Reading:
http://www.cameralabs.com/reviews/Tamron_SP_150-600mm_f5-6-3_Di_VC_USD_G2/verdict.shtml
http://www.cameralabs.com/reviews/Tamron_SP_150-600mm_f5-6-3_Di_VC_USD_G2/index.shtml
http://www.cameralabs.com/reviews/Tamron_SP_150-600mm_f5-6-3_Di_VC_USD_G2/sharpness.shtml
My $0.02 worth.

jeep_daddy Loc: Prescott AZ

I've got a friend that says his Tamron SP 150-600mm f/5-6.3 Di VC USD G2 is much sharper than the previous version. I think it's about $1500 from what he said. He got his for Christmas and loves it.

amfoto1 Loc: San Jose, Calif. USA

You're lucky it isn't 2012, when there weren't many truly long focal lengths that were both affordable and worth a damn (Sigma made a few that reached 500mm). Now there are a lot of choices.

Since you're shooting with Nikon gear, the very first lens I'd look at would probably be the $1400 Nikkor AF-S 200-500mm f5.6 VR (FX). You might want a 1.4X teleconverter to use with it, too. I don't know much about the various Nikon TCs... you'll have to research those yourself. The Kenko Pro 300 1.4X DGX may be a pretty good alternative and currently costs about $130. (I shoot with Canon gear and wasn't aware of the minimum focus distance limitations with this lens, that someone mentions in an earlier response. But I always carry a set of macro extension tubes and have often used them to improve close-focusing abilities of long telephotos that normally couldn't be used so close. Just a thought... and a relatively simple, inexpensive solution. The last time I looked, a set of Kenko Macro Extension Tubes cost about $120. While the longest in the set.. 36mm... won't make possible actual macro work with 300, 400, 500mm lenses... it will make them much more close-focusing.)

Of the third party lenses, the Sigma 120-300mm f2.8 DG HSM OS ($3400) is the fastest option under $10,000. It is rather big and heavy, so be fore-warned. It also appears to work pretty darned well with high quality 1.4X and 2X teleconverters.

The Sigma 150-600mm OS HSM "Sport" ($2000) is the next option, better built and overall higher performance than other similar lenses. The "Sport" is also bigger and heavier than other similar lenses.

The Tamron 150-600mm "G2" VC USD ($1400) seems pretty close to the Sigma "Sport" in image quality, maybe even a little better, but may not quite match it for focus speed and build.

The original Tamron 150-600mm and Sigma 150-600mm "Contemporary" (both roughly $1000 or maybe a little less) are the lightest and cheapest, with a little bit of compromise in build quality/materials, image quality and overall performance... but are still a lot better than much of what was available for less than $10,000 prior to their introduction in 2013/2014.

You can find all sorts of reviews, test results and comparisons of any of these online.

homefree21

Hey Bill,
Have you used it with the teleconverter? I'm needing more reach and the 400 was not long enough or sharp at the long end. Never been happy with it or the bokah. I'm not quite ready for the $5000 lens but possibly soon. Right now just looking for the best lens with the most reach that is sharp. My camera skills and holding are good, just confused on which one. I was going to get the sigma sport before the tamron G2 came out but since I haven't been happy with the Sigma 120-400 I was skeptical. Was going to rent but really its a no brainer when you have a 30 return policy. Not expensive enough to throw a couple hundred down the drain. If I splurge for the Nikon it will be in the next 2 years and hopefully they will make something to compete with the Tam and Sig with a little better optics and works. I would def spend $5000 if it was a 200-600mm.

homefree21

Thanks CO,

I was aware of the problems with the older Tam so didn't purchase it. The new one has many good reviews, of course there are always negative to all, which one works best for each person is the issue. Obviously I'm not sure.

homefree21

Thanks, yes I read these, very good reviews, pushed me towards the Tamron but you know, still throwing it back and forth. Thats why I wanted some feedback which is very much appreciated!

homefree21

Thanks Bill

homefree21

Thanks Jim,

Have this lens and do love it for walking around in towns and such or a casual hike. Just want more reach that it can give.

Architect1776 Loc: In my mind

My thought exactly. You throw a crap load of money on bragging rights for a camera then want to go on the cheap for a lens. Get a D5300 and Nikon glass and do a whole lot better in you images.

whitewolfowner

Many on here do not like the Tamron first edition 150-600. My son owns one and it is a great lens so I do not understand it being rated here as it is unless there are good and not so good copies out there. We happen to have gotten a good one and so has another hogg I've been conversing with. The new Tamron is supposed to be much better and has matching teleconverters for it too. If you already own any nikon auto teleconverters I would suggest the Nikon 200-500. If not the new Tamron does reach out 100mm more. The older Tamron is going for I believe either $700 or $800.

homefree21

So Thank you all for your comments and suggestions! I have read and took into consideration each and every one. I think I am going to start with the Tamron as most reviews say it has sharper focus through out the frame where Nikon has razor sharp center but with soft edges and corners at most focal lengths. The Nikon 200-500 F5.6 also has a large VR shift, wonder if anyone has noticed? The sigma sport would be my other choice but it seems the Tamron may be better for my purposes as of now. I will put up some samples when I get it. Comparing the sig 120-400 with this Tamron will be interesting. I have found also as I go through my images that I tend to use close to the 400 on every shot. I really don't want to crop much.