SunBeach1962 Loc: Syrscuse, NY

I have a Nikon D5500 crop format, about 7,000 clicks in mint shape. Kit 18-55mm lens, upgrade kit 55-300mm. A used 35mm DX. I like to shoot wildlife, sports, grandchildren. Feel the need for longer focal length, I rented a Tamron 150-600, it was too heavy, I am 68 not in great shape. Also bought and returned Sigma 60-600, also too heavy. So I am now looking at the Tamron 100-400mm, review says light weight, but lousy focus at a lot of points, does anyone have any input on this lens?
Or should I go for a full format D850, is the glass any lighter for the same quality?

CHG_CANON Loc: the Windy City

Your wildlife needs are going to start at 400mm no matter what format camera you have. Full frame cameras are nearly always larger and heavier too. If you want to experiment with a few other lenses, try the:

Nikon 500mm f/5.6 PF
Nikon 300mm f/4 AF-S FX with a TC-14E teleconverter option
Nikon 180-400mm f/4E VR FL TC FX

Your camera is fine for your needs until you determine the lens(es). Any of the Nikon 70-300 models are useful general purpose lens for the grandkid's sports. They're relatively cheap and will focus faster than the 55-300 DX. Sign-up for the email list from LensRentals.com for regular discount codes and try some of these options for a week's investigation at a time.

RWR Loc: La Mesa, CA

The weight of any given lens is listed in the specifications. The choice is yours. The only thing I can tell you about the Tamron is that it is a variable aperture lens and covers a wide focal length range - I would not own it.

ELNikkor

The D5500 with a 70-300 plus a little crop should get you effectively out to what a 500 would get in FF. If weight is a factor, I would not go to FF at all. A Nikon 200 -500 would be an efficient way to get out around 750mm (FF effective) on your D5500, but even that lens would need a tripod or monopod. I would suggest you consider a bridge camera. Other Hoggers get great results from Nikon P900 or Canon SX60 or SX 70.

BebuLamar

I think CHG_CANON has listed the lightest lenses. Having full frame camera you will have to have heavier lenses to provide the same angle of view.

DaveyDitzer Loc: Western PA

Ditto. The 5500 is a good camera for wildlife and long reach. I don't think you will be happy with a FF and the D850 is heavy. I have 55-300 DX which is good for wildlife across a small pond. I also have a 200-500 and like it but it's 81oz and needs a tripod. I had and sold a 300 f4 - it's not enough. The d5xxx series are nice light bodies but that makes the heavier lens seem even more so. I think the super zoom bridge camera is a good answer to your question. Now if you can rent a 200-500 and put it on a monopod ball head so you get support of the weight with freedom of movement for active wildlife.

Contemplate Loc: Conroe, TX

I’ve got my asbestos underwear on so here goes. Olympus OM-D E-M1 mk3 with Olympus 40-150 f/2.8 and Olympus TC2.0. Gives you FF eq 160-600 f/5.6 in a lighter, better handling package. All IMHO of course. Rent one for a week or two from lensrentals.com you’ll buy it.

—jim

ClarkJohnson Loc: Fort Myers, FL and Cohasset, MA

I agree with everyone who recommends staying with crop format bodies. If you really want the best body for wildlife, you could check out the D500, but even that is heavier than your D5500.

I have both the Nikon 300 PF/TC 14 combo and the Tamron 100-400, and I love them both on my D500. The Tamron would both the more versatile and more economical upgrade. IMHO it is a vastly overlooked gem of a lens. Very easy to handhold. I have larger lenses as well, but the Tamron is what I would take on a birdwalk.

Good shooting!

Architect1776 Loc: In my mind

You camera is just fine.
Go with lenses like you are doing, try renting from places like Lens Rentals.
If you go D850 you will want FF lenses and really start adding weight including a much larger and heavier camera body. You are sensitive to weight and D850 is not the way to go.
go to various lens sites see what they have including Nikon.
Look at weights compared to what you already have tried.
Then rent. Only YOU can determine if the weight is right for you.
But the heavy D850 and heavier and large FF lenses is counter productive in your search.

jerryc41 Loc: Catskill Mts of NY

The D850 would be a big step up from the D5500, and I bet you'd love it. As for lenses, you would want good glass for a good body. Get the D850, a "normal" zoom, and a longer one. Go for it!

Lenses -
https://www.dpreview.com/news/5585760175/nikon-releases-official-d850-lens-recommendation-list
http://www.dslrbodies.com/cameras/the-d850-blog/the-best-lenses-for-the.html
http://cameratimes.org/best-lenses-nikon-d850/

wildweasel

like me I believe you are a good candidate for the Olympus EM 1 Mark ll and the Panasonic/Leica 100-400 lens. This combo is about as small and light as you can get, and the 2X crop factor of micro 4/3 will get you a field of view of 200 to 800 mm. But for even lighter weight, the Olympus 75-300 lens . I am 66 and got tired of the back ache and shoulder ache of my D750 and Tamron 150-600 G2. For the past 3 years now photography is fun again.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

If your needs are wildlife, then stick with the 5500, a cropped sensor camera can reach out more than a FF. And, since you said weight is a problem, the D850 is a monster, you should not consider it if weight is an issue.
I do not shoot Tamron or Sigma lenses so I cannot help you.
For general photography like grandchildren my favorite lens has always been the Nikon 18-200 II. The Tamron 100-400 would give you and field of view of 150-600. I believe 150mm is sort of long for grandchildren, you'll be constantly moving back from them, and that lens is also slow.
I keep hearing weight is an issue,
The Tamron 100-400 is 2.45 lbs.
The Nikon 18-300 DX is 1.21 lbs.
Just sayin. You keep sayin weight is an issue.
And for wildlife, unless you want to carry a tripod, their is no such thing as a light weight lens that reaches out to 600 mm, which is what you need for true wildlife photography.
The Sigma 150-600 is only 4.03 lbs. And you said already that it was too heavy.
So, my suggestion, for what it's worth, get the Nikon 18-300, it would work great for the grandchildren, and then learn how to get really close to wildlife.

uhaas2009

On my 810 with 70-200. 2.8 I put the tripod foot back on the lens and set the foot on my hand when I shoot handheld. This way it feels more balanced and comfortable.
try the 200-500mm.....

out4life2016 Loc: Bellingham, Washington

I have shot with the Tamron 100-400G2 series lens and actually really like it. The focus is fast and image quality is great. It is a nice light lens that I think you should rent and see. A girl friend of mine who is in her upper 50s shoots it all the time on her canon 80D with no problems even hand held on long days out.

Kaykeeko

I shoot the Tamron 100-400 on a DX Nikon. Great lens. Lightweight and responsive.