jerryc41 Loc: Catskill Mts of NY

Look for comparisons of those lenses, and search for "speed." Of course, all other qualities will be important, but it's hard to imagine a Tamron getting a better overall rating than a Nikon lens.

Tamron - 100-400
https://digital-photography-school.com/review-tamron-18-400mm-zoom-lens/
https://www.dpreview.com/samples/9152094990/gallery-impressions-tamron-18-400-f3-5-6-3
https://www.pcmag.com/review/358561/tamron-18-400mm-f-3-5-6-3-di-ii-vc-hld
https://www.thephoblographer.com/2017/10/30/first-impressions-tamron-100-400mm-f4-5-6-3-di-vc-usd/
http://www.imaging-resource.com/lenses/tamron/100-400mm-f4.5-6.3-di-vc-usd/review/

Nikon/Tamron Various -
https://www.bhphotovideo.com/c/compare/Tamron_100-400mm_f_4.5-6.3_Di_VC_USD_Lens_for_Nikon_F_vs_Nikon_AF-S_NIKKOR_200-500mm_f_5.6E_ED_VR_Lens_vs_Nikon_AF-P_NIKKOR_70-300mm_f_4.5-5.6E_ED_VR_Lens_vs_Nikon_AF-P_DX_NIKKOR_70-300mm_f_4.5-6.3G_ED_VR_Lens/BHitems/1362803-REG_1175034-REG_1349415-REG_1275036-REG

Nikon/Tamron -
https://photographylife.com/nikon-200-500mm-vs-tamron-150-600mm-vs-sigma-150-600mm-c/1
http://www.davemclelland.com/nikon-200-500-vs-tamron-150-600-lens-comparison/
http://www.davemclelland.com/nikon-200-500-vs-tamron-150-600-lens-comparison/
http://www.photozone.de/Reviews/296-tamron-af-200-500mm-f5-63-di-ld-if-sp-lab-test-report--review
http://www.bobatkins.com/photography/reviews/tamron_200_500.html
http://www.imaging-resource.com/lenses/tamron/200-500mm-f5-6.3-di-ld-if-sp-af/review/

dgingerich Loc: Cape Coral, FL

I've never had a Tamron so I can't give you a comparison. But I love the sharpness of my Nikon 200-500 on my D750. Consistently tack sharp. I use it on a monopod a lot more than handheld. I've only had one third-party lens and that was the Sigma 50-500 and I could never get sharp photos with it. Might have been just a bad copy or a bad model. But never been disappointed with my Nikon.

imagemeister Loc: mid east Florida

To me, hiking and camping means that WEIGHT/size could be an issue - meaning the Tamron is a better choice. BUT, if your "main concern" is AF speed, then the Nikkor is a better choice and be ready, willing and able to manage it.
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Lagoonguy Loc: New Smyrna Beach, FL

I have the Tamron 100-400mm and recently added a D500 to my D750 & D7100 for the sole purpose of bird photography. It delivers consistently very sharp images in good light and it is a pleasure to manage while hand holding. The lens only weighs 39+ ounces. I am blessed to have osprey, owls, hawks, herons, ibis and all manner of other wading birds and smaller birds within 200 ft of my back veranda on a river in Florida and this lens can handle all of that very well in reasonable light. I am 75 and in good health but the weight issue is lurking so I got a 4/3 G9 outfit that takes me out to 560mm, in 35mm equivalents, and it is also amazingly effective except for BIF where it does not work as well as the D500/Tamron 100-400 combination. The G9, lens and TC only weighs 50 ounces. The Olympus system will handle the BIF situation better but apparently not as well as the Nikon solution or at least from what I’ve read. I can and do get good photos at dawn and dusk with the Tamron but I do get some focus hunting at times. If I go crazy and and buy another lens for further reach it will probably be the Nikon 500mm PF because it only weighs 51 ounces but it may be a terminal acquisition because at $3600 my wife will put an end to me. Good luck!

ClarkJohnson Loc: Fort Myers, FL and Cohasset, MA

I have both of these lenses, and I much prefer the Tamron for daily use because of the weight. For those times when a tripod is appropriate, the Nikon 200-500 would probably be on it, or even something longer, but for quick handheld shots, the Tamron 100-400 has yielded some superb images.

I know that you will get many other suggestions, but let me throw in my other favorite for handholding: the Nikon 300PF paired with the TC 14III teleconverter. Also very light and excellent IQ. I had that on my D500 this morning for a walk at the local Audubon Preserve.

Good shooting, whichever you choose.

suntouched Loc: Sierra Vista AZ

Consider the Sigma 100-400 mm lens or the 150-600 mm contemporary lens or the Tamron 100-400 mm lens. All will perform well. Good-great image quality, good focus acquisition, nice bokeh. All are priced within reason. For a couple of years I used the Tamron 100-400 mm lens with the Nikon d7500 and it was a good fit. At the moment I am shooting Canon with the Sigma 150-600 mm c lens and have been very happy. I am loving the extra focal length over the 100-400 mm. No lens extender to buy or worry about. Weighs out at about 4 pounds which is significantly lighter than the Nikon 200-500 mm lens. The Sigma 150-600 mm c lens is currently on sale for 899.00 if that matters to you. I was on the waiting list for the Nikon PF 500 mm lens but my name never seemed to come to the top. Had it I would still be shooting Nikon and loving it. I never considered the Sigma 150- 600 mm lens for the Nikon d 7500- thought it was too heavy for me to handle but it's not and I do regret changing systems sometimes.

suntouched Loc: Sierra Vista AZ

PS- whatever you decide to get, pick up an OpTech harness strap for about 25.00. It gets the weight off your neck and re distributes to back, chest and shoulders. And the strap attaches to your camera lugs and not the tripod connection. It has made such a difference to me carrying a heavy lens. I routinely hike 2-3 miles (with the Sigma 150-600 mm) on fairly level ground without undue physical fatigue and the camera is always ready to shoot. And it provides a little counter resistance that helps your stance.

MiroFoto

OK, I suggest ...wait a few days. I do not have profi and expensive gear. But my Tamron lens 16-300 just left my house for the repair - second time the same issue - focusing went stuck and getting worse every day …. and I do not shoot many pictures. Yes they have 6 years warranty … but what you do after it?

Miro

tcthome Loc: NJ

Another vote for the Nikon 200-500 with the option to add the 1.4 tele later.

DaveO Loc: Northeast CT

The 1.4 doesn't quite provide the clarity I'm looking for on the 200-500 or 150-600 G2. When I bother to use them I typically use manual focus. I would not buy them again. Plus, no matter how long the focal length, it's never quite enough! LOL! I spent a month in Yellowstone last year with a 600 F4E, a 1.4, 1.7 and a 2X. The 1.7 was pretty darn good!

Lagoonguy Loc: New Smyrna Beach, FL

Hi Suntouched, I wondered where you ended up with your quest for the perfect camera/lens combo. Glad to hear you are happy with the new gear. Thank you for guiding me away from the Panasonic 100-400 and the various issues that it has experienced. I did get a nice G9 P/L kit but stopped with the 50-200 w/TC, which is a great kit for most of my travel photos, not that I’ve been doing much of that lately, but went with the D500/Tamron 100-400 for wildlife. I don’t have the need yet for the 500-600mm range due to my location but I may get one down the road. The D500 is great for BIF for me but I am truly a novice. Stay safe.

The Capt.

I shoot only Nikon cameras and lenses and always will. My equipment includes a Nikor 200-500, a D3300 and a D850. Be aware that the 200-500 is an FX lens. It will still give excellent pics on crop sensor. But no matter what you choose I recommend that you learn post processing.

suntouched Loc: Sierra Vista AZ

My quest tells me there is no perfect camera/lens combo but I keep trying. I am helping to keep the economy alive!

Jomisamson

Being relatively new, I’m not familiar With the DXO site you mentioned. Could you please send me a website address I could explore?

RickL Loc: Vail, Az

Consider using the Tamron 150-600 G2 lens. It is lighter then the Nikon and is exceptionally sharp at all focal lengths. My wife and I both have our own. Mine is mounted on a Nikon D850 and hers on a Nikon D7200.

Enjoy your photography whatever you choose.


Rick