Checking in a bit late but you definitely need glass that can keep up with those tiny pixels. The R7 sensor density is basically like a 90MP full-frame sensor, so it really punishes anything mediocre. Honestly, the glass quality matters way more here than it did on older bodies. If youre okay with a fixed focal length, here are a couple of decent options:

• Canon EF 400mm f/5.6L USM (used)
• This is a pretty solid classic. Even without IS, the optics are much better than cheap kit zooms and it autofocuses fast enough for birds on the R7 adapter.
• Canon RF 600mm f/11 IS STM
• You can usually find a used copy around $500. Its super light and easy to carry while hiking in the Smokies. The 600mm gives you tons of reach, though that f/11 means you need decent light. Just dont expect miracles in deep woods shade... you gotta have some sun to make that sensor really sing.

> Need something sharp for backyard birds under $500 before my trip to the Smokies... I saw your post and totally get the struggle with that R7 sensor! Its super picky. You absolutely have to look at the Canon RF 100-400mm f/5.6-8 IS USM. I know it looks like a dark lens on paper, but its basically fantastic in real-world use. One thing that makes it perfect for a trip to the Smokies is the weight... its like carrying a water bottle compared to those old EF bricks. My old gear used to give me such a backache after an hour of hiking, but this thing is light as a feather. What really blows me away is the close-focusing ability. You can get surprisingly close to subjects, which is amazing for birds on a nearby branch or even big insects. Since youre on a budget, definitely check the Canon Refurbished site. You can often snag it for way under $500, which leaves you extra cash for more SD cards! The stabilization works in tandem with the R7 internal sensor shift too, so you can get sharp shots even when youre handheld and feeling a bit shaky. Youre gonna love it! If you have more questions about the settings I use for birds, feel free to ask.

You seriously need the Canon RF 100-400mm f/5.6-8 IS USM! It has incredible Nano USM speed and sharpness that handles the R7 high-res sensor like a total pro!