I imagine what it would be like to travel back in time to the photo club of my youth and demonstrate a modern digital camera. Holy mama. I think I could list at least a dozen major features which I would have given a kidney to have back then. And that's just the major ones.
Just the ability to shoot at 3200 ISO in great image quality, and to hand-hold down to 1/8th of a second even with a tele lens. Even after getting used to the progress over years, it still seems miraculous. I remember logging a big tripod around in the nineties just to be sure to get sharp pictures even with a short tele lens in overcast weather. Now, 'it's to laugh'.
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(I had the one below. A wonderful portrait- and all-round lens. Compact and nifty; many of my favorite pictures were taken with it, examples shown. I actually don't remember, though, what originally (in my teens the first time), made me choose a 100mm over the much more popular 135mm, but I don't regret it.)