For beauty & photography, Cinque Terre Day-Trip delivers.
Keep the brutal-honesty knock: it's 2.5–3 hours each way with a change at La Spezia, so on a day trip you spend more time on trains than in the villages, and in summer both are mobbed and sweltering. What the day actually feels like for that effort: a tight, hot loop of arriving, queuing for the regional train, half an hour in Vernazza's crush, a packed swim or a sweaty stretch of the coast path, then the long haul back at dusk — exhilarating in glimpses, exhausting in aggregate. It's genuinely spectacular, and it's the wrong shape for a day trip from Florence; if you can't give it an overnight, Lucca or Chianti repay the same hours far better.