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Why do zoom lenses and compact cameras have varied maximum aperture across the zoom range?
Just starting out with lacrosse pictures on my new Canon EOS 60D and zoom lens EF 70-300mm f/4.0-5.6 IS USM. Why can't I set aperture at 4.0 and it stay there? Why does the aperture get smaller as I zoom in? I just discovered that this happens. I just thought I couldn't dial to 4.0 and couldn't figure out why wouldn't go any larger. Doing all in Manual mode. I hope this isn't as stupid as it sounds, but I think when I learn the answer I will have a lightbulb moment and really grasp this. Thank you for anyone's input.