This is my opinion. I've owned the Lumix 100-300, the Olympus 75-300, Lumix 45-175, Olympus 50-200, Olympus 300mm f4 Pro, Sigma APO 300mm f4 Tele Macro, Canon nFD 80-200 f4, Tokina 60-300, Canon EF 300mm f4, Nikon 300mm f4 AFS, Pentax-M 200mm f4, Nikon AIS 200mm f4. I used them all with the Olympus EM1 or EM1.2.You can get great photos with all of those lenses, depending on light conditions. Even the Pentax, which was never a sharp lens, from the early 1970's can be used to take great photos in the right conditions. Camera makers want us to buy more lenses, so they talk to reviewers about whether lenses are too sharp for sensors and that's all just marketing.
What matters in the field most is aperture and focus speed. With some practice you can make a 20-year lens old focus pretty fast for BIF and a lot of things. I find it more satisfying to work with that lens than with a $2000 modern equivalent, and I'm consistently pleased with the results.
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But when it comes to modern lenses, even the Lumix 45-175 can take great photos. If you think 175mm is too short, you can walk or drive closer, or reframe the shot.
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