This is the first 600mm lens you can actually hold in your hands, which is a plus for hobbyists. It only weighs 2 pounds and is a good balance for my Canon RP camera. The OS system works well. I can understand why this is not a pro lens as STM and mirrorless focusing are not fast enough and F11 is too weak for pros. The lens is also not suitable for all weather conditions. But these applications are not mission-critical for most bird lovers. If you're looking for a lens that's easy to take off your neck on a sunny day and leave your tripod behind, this is the lens for you. Works well on cloudy days. However, ISOs above 10,000 introduce visible noise and reduce sharpness. On a sunny day, when ISO is below 1000, Canon's Digic 8 processor delivers completely silent, full-frame shots that are amazingly sharp. That's why I'm keeping it. In low light, amateurs like me won't be trying to shoot birds and will take other fast, weatherproof lenses. I like the large focus ring and focal length indicator in the viewfinder, which really helps with manual focusing and complements the slow autofocus. It works and there are no tight muscles anywhere, making the hobby more enjoyable than work. To give you another AF tip after a few days of use, set your camera to Servo AF instead of Single AF, which is much faster with such a long STM lens. This will drain the battery faster, so buy a few more batteries.
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