I am making this post of my first trip with the Tamron 150-600 G2 to the Riverwalk Parkway in Riverside CA. A place I used to visit weekly for the water birds. It is a man made "river" with rapids, dams, bridges and a series of connected ponds about 1 mile long. There are foot and bicycle paths along it, sometimes on both sides and foot bridges to connect a light industry/business office/tech schools zone on the East side of it to the West side where the bus stops and shopping center with a Starbucks is located. The main pond has an island with a roofed observation platform reached by a wooden foot bridge. The water comes from a combination of storm drains and water purification ponds that are part of the city sewer system. It is built in a large flood control channel running beside a main street from La Sierra University on the North to the main flood control channel beside the CA 91 Freeway at the South end. The park was the idea of a local industrialist and a combination of his company, some others in the area, the university and the city park de

I went to Magnolia Bird Farm (a very large bird and other pet food company with bird breeding facilities in Riverside CA. They also have a few rescues living in the facility beside the breeding for the pet stores in a large area of So CA. They buy in bulk and mix and pack the various foods in their own brand and for others. I picked up some Nyger seed (only $1.39lb), then stopped at the Riverwalk Parkway on my way to Costco and home. Among the ducks was a pair of Hooded Mergansers. There were lots of ducks and Black Necked Stilts and one small uncooperative Snowy Egret. I put most of my time on the Mergansers. I did 302 shots and after the first cull I am down to 145 and will probably get down to only 50 or so keepers.
The male was my first frame and the female was near the end of my shots.
#1 the male out in the middle of the main pond in weak watery afternoon sunlight.
5DIV, Tamron 150-600 G2 @ 600, 1/400 @ f/7.1, ISO 640 hand held
#2 the female was cruising in the north west part of the pond in shade. I used LR to warm the colors to look more like the image of the male.
5DIV, Tamron 150-600 G2 @ 600, 1/500 @ f/8.0, ISO 4000 hand held

Note the ISO 4000, the 5DIV handles higher ISO very well.
I would say that the Tamron 150-600 G2 did a very good job.

Thanks, Robert and I was on the B & H waiting list for the GI version and never made any adjustments to tune it but did aim it at a buoy about a quarter of a mile away at 600mm and its numbers were very clear and sharp and have used it with the D7100 since then with no complaints, and just wondered if you had made such a comparison. I have a feeling that I would not see enough difference to justify the cost and may wait to make a change until the G1 starts giving me problems! I think that given my choice I would rather first invest in a new body and was thinking of the D500, but have read that its iso performance under low light conditions is no better than the D7100 and that would be my main reason for making a change, so maybe will just stay with what I have now. I use the 18-140mm kit lens for close-ups like butterflies or landscapes and a have the 70-300 which also came with the camera, but not as satisfied with it as it seems to be a little slow focusing but may be that I really don't use it enough to become used to it! Thanks again and take care!

I was using the G1 with a 6D (they seemed made for each other) and a 7DII - the 7DII and G1 did not play well together. I called Tamron and they had me mail it to them and they did two firmware upgrades and tuned it. The day after I got it back Canon released a firmware update for the 7DII that solved the same problem - after that the combo worked great. My 100-400 mk 1 and later mk 2 were a bit sharper and faster on AF but of course for small birds didn't have as much reach.
The G2, just like the G1 seems to play better with a FF. The results with my 80D are very good, the results with my 5DIV are great.

I was on the list for a G1 and just dropped into the local camera shop on the chance I could look at one. They had just opened a box with their first 4 they received, 3 were pre-sold, #4 walked out the door with me so I actually got mine first. They displayed some moon shots I did with it as examples of what it could do for about 6 months.