24 bit deferred lighting engine.
Killzone Shadow Fall:
1080p
1920 x 1080 = 2,073,600
2,073,600 x 8 bit colors x 24 bit = 398,131,200 bits
Divide by 8 to turn into bytes: 49,766,400 Bytes
Divide by 1024 = 48,600 KB
Divide by 1024 = 47.46 MB
~48 > 32
BF4 PS4 (uses same bit depth)
900p
1600 x 900
(((1,440,000 x 8 x 24) / 8 ) / 1024) / 1024 =
32.96 MB
32.96 > 32
BF4 XB1 (uses same bit depth)
720p
1280 x 720
(((921,600 x 8 x 24) / 8 ) / 1024) / 1024 =
21.1 MB
21.1 < 32
Moral of the story, eSRAM is a limit for game engines with dynamic lighting,
EDIT: All of this excludes MSAA which would increase this even more.