Test backfocus, if you zoom all the way in and focus, and pull all the way out and it's not still in focus, you have a problem.
That lens is not parfocal, this test won't tell you anything useful .
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Test backfocus, if you zoom all the way in and focus, and pull all the way out and it's not still in focus, you have a problem.
Use a monitor, you can't rely on the camera lcd alone, unless maybe if you have a magnifying loupe.