I agree with the recommendations to replace that EF 75-300mm III lens with something better... That's the cheapest telephoto zoom Canon makes. It has slow micro motor focus drive, no image stabilization and marginal image quality, especially toward the 300mm end of the zoom range.
The EF-S 55-250mm IS STM would be an excellent choice and sells for $299 new (plus $23 for the Canon ET-63 lens hood, highly recommended). Possibly less refurbished or used. This lens has faster/quieter/smoother STM (stepped motor) focus drive, helpful image stabilization and better image quality.
Alternatives are the EF 70-300mm lenses. There have been several, any of which would be a solid improvement over that 75-300mm.
EF 70-300mm IS USM "II" is the currently available model. It sells for $599 new (plus $45 for Canon lens hood ET-74B). With USM (ultrasonic) focus drive. In fact, this particular lens was one of the first to get "Nano USM", which is quiet and smooth like STM, while still being even faster. It also has IS and very good image quality.
The original version EF 70-300mm IS USM was superseded by the "II" around 2016, but might be found used and can still be a quality lens. I didn't find any used copies with a quick search, but am sure you can find them. I don't know what they tend to cost now. This lens uses Canon lens hood ET-65B.
EF 70-300mm IS USM "L" has been discontinued, but is the only 70-300mm that can optionally be fitted with a tripod mounting ring (sold separately). As an L-series, it's more robust and better sealed than the other lenses listed here. It is also larger and not quite double the weight of the other 70-300s. Of course, it has USM focus drive, image stabilization and very good image quality. Like most L-series telephotos it comes with a matched lens hood and is painted off-white. When it was available new, the 70-300mm L sold for around $1300. Now it's about $700 to $1000 used, depending upon condition. Separately sold Canon Tripod Ring "C" costs $169 new, but appears to be out of stock most places. Alternatives are used or 3rd party rings.
EF 70-300mm IS USM "DO" is a discontinued lens that uses "diffractive optics" to be more compact than any of the above. It is not any lighter weight, though. In fact, it's about the same as the first two 70-300s. A friend of mine used this lens quite successfully for sports photography. As you can see, it has both fast USM focus drive and helpful image stabilization. It uses the same, separately sold ET-65B as the 2nd 70-300mm above. When it was available new, this was the most expensive EF 70-300mm at about $1400. I've seen it selling used for between $400 and $600, depending upon condition.
If you don't need all the "reach" offered by the above lenses, there also have been a number of excellent Canon EF 70-200mm lenses. There are both smaller f/4 and brighter f/2.8 versions. All are L-series and all have USM focus drive. I recommend the versions with Image Stabilization (only the oldest versions don't have IS).
If you need even more reach, there have been two versions of Canon EF 100-400mm. Both are top quality. The "II" has superb image quality and the guys at Lensrentals (who enjoy taking things apart, just because they can) called it the most robust, well-built zoom they had ever seen.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
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