A 150-600mm Tamron G2 mounted on a crop sensor Nikon D500 giving me an "effective focal length of 900mm. Used 50/50 on a monopod with an arca type clamp for the lens, or the whole rig mounted on a Gimbal headed tripod. I find I'm using the monopod more for hummingbirds and butterflies, and the gimballed tripod for larger targets, such as stationary birds, or birds in flight. And this lens, to answer your original question, gives me ALL the reach I need at that 900mmFL, and this lens is also PLENTY sharp at a bargain price!
I would go for a Yongnuo 568EX, or better still, a Yongnuo YN 685, which has radio slave capabilities as well!.. I do own a Nikon SB800 about 10 years old, and if you can get a used one with a warranty for less than $200..Go for it..Otherwise the 2 Yongnuos go for around $100 ea.. Buy from a reputable dealer such as B&H, or Amazon.
AMEN on Photoshop CC..I have never used Lightroom to any great extent..My work starts in the camera as a RAW file opened in Photoshop CC2017, and edited from there..Today's Adobe Photoshop is BETTER than ever..Virtually all images I capture are with the intent of making a print, and Photoshop has been helping me towards that end since 1999. I do however use some 3rd party plugins in addition for certain features. Topaz Denoise, for example, is the BEST noise removal tool I've found, and it's usually my 1st step following the opening any image from RAW..
I ALWAYS shot in RAW mode..Color temperature fix is just ONE slider away in Adobe Photoshop CC 2017..No worries..
I've owned an frequently used the Tamron 70-300 VC, and have had some stellar results..It has bee favorably compared the most previous iteration of the Nikon 70-300..Some actually think it's sharper!..The vibration control is fantastic on this lens, and it does come with a 6 year manufacturer's warranty as long as it's purchased from an authorized USA supplier.. I purchased mine in 2012 when I also bought my Nikon D7000 (which has since been converted for infrared only capture). Tamron often has rebates on this lens as well. This past year I purchased a Tamron 150-600mm G2 to go with my new Nikon D500!..I have lots of confidence in the Tamron brand!!
Virtually ANY modern day 90-105mm 2.8 will do the job for you..I personally own a non-D Micro AF Nikkor 105mm f2.8 that I bought used about 15 years ago with very few miles on it..It's the sharpest lens I own, and use it in manual mode currently on my Nikon D500, but also used it with a Nikon N90s film camera back in the film era.. I've also owned several Sigma's and Tokinas..They ALL gave me excellent results!!
I have a microtek 4000DPI "SCSI" interface scanner!..Anyone got a "cure" for this one??
I own the Tamron 150-600mm G2 and have it coupled to a Nikon D500..The BEST birding combination I've owned!!..Check out images from in FB on the "Tamron 150-600mm Owners Group"..I think you'll be amazed..I'm getting incredibly sharp images WIDE open at F6.3! Be sure to look at images from Steve Shaluta, Larry Venus and Lewis Kemper!!
Eddie (pahtspix)
I personally think that you will see a beautiful images coming out of a D7200, which for your description of how you shoot , will give you much larger images and better low-light capability and image quality..Incredible bang-for-the-buck..You should be able to get one of these at way less than $1000.. BTW, my own D7000 has been converted to an infrared only camera, ad it fits the bill quite nicely for that purpose.
I've been using BBF exclusively since Steve Perry came out with his first video on the subject..My capture ratio has improved exponentially! (THX Steve!!)
Take about $100 USD, and purchase a Yongnuo YN685 for Nikon (available from Amazon, B&H, and Adorama to name a few) It will do most everything that a Nikon brand flash will do, and much more than ANY Vivitar ever made..Do NOT even THINK of taking a chance with that old Vivitatr..If in fact it's 50 years old, it problably and most likely fry your sync contacts..
Amazon has a GREAT reputation for taking care of their customers..I'd contact them, and tell them what's going on..I wouldn't be surprised if they replaced your tripod.
I've been using Back Button Focus for almost 5 years, and it has improved my image captures exponentially! Steve Perry's advice has been worth its weight in "Pictures!" His explanations are very easy to follow..
Amazon.com : RFN-4s Wireless Remote Shutter Release for Nikon ...
https://www.amazon.com/RFN-4s-Wireless-Shutter-Release.../dp/B005PCDSBQ
Rating: 4.6 - 443 reviews Around $60 USD at Amazon, with GREAT reviews on this sender/receiver shutter remote set..I'll be ordering one for my D500. My hotshoe is taken up with yongnuo radio remotes for my flash set up..This unit here, goes into you 10 pin connector as the receive to trip your shutter with the remote contoller that can be up to 300+ feet away..AMAZING!
Amazon.com : RFN-4s Wireless Remote Shutter Release for Nikon ... Inexpensive radio remote that plugs into the 10 pin remote on your D500, along with a remote trigger that will work around 300 ft away!! I'm gonna get one! around $60 usd
https://www.amazon.com/RFN-4s-Wireless-Shutter-Release.../dp/B005PCDSBQ
Eddie..AKA "PAHTSPIX"
Rating: 4.6 - 443 reviews