I had the Leica 135mm APO-Teleyt-M mounted on the Sony A7r via a Metabones adapter. The maximum aperture of the APO-Telyt-M is f/3.4, which I selected to give me the shallowest depth of field that would isolate the birds sharply against the out-of-focus tree branches. With the Leica lens this is a manual focus situation, of course, and I relied on the focus peaking feature of the A7r to outline the birds in red when they snapped into focus.
Here are a few samples, all shot manual focus with a wide open lens:
|A House Sparrow, one of the more common birds in the city.|
|A White-Throated Sparrow looking like a little fur ball.|
|I actually like the shots best when there are a lot of branches so the bird blends into them, as this puffed-up White-Throated Sparrow did, even with his color.|