Of course there’s a big difference- two generations of signal processing (ignoring the fact for a moment that different lenses look very different) and chip development. I’d be pretty disappointed if the T4i didn’t look different from the T2i- otherwise just but a used T2i for way cheaper. So if you need these two cameras to closely match- you need to sit both of them down connected to broadcast monitors and waveform/vectorscope with test charts and adjust them carefully to match.
Noah
Call Box Training.
Featuring the Panasonic GH2 and Panasonic AC160/130.