Safe jumps are key part of many fighting games, including Super Street Fighter IV: Arcade Edition ver. 2012. For conventional safe jumps, the tightest possible set-up in the SFIV series is 4 frames: 1 frame of a meaty jump attack, 2 frames of jump attack landing recovery, and a return to a neutral state on the 4th frame. A proper set-up will allow the attacker to guard against invincible reversals with 4 frames of start-up, such as Ken’s M or EX Shoryuken (but not his L or H Shoryu, both of which have a start-up of 3 frames).
Recently, Makoto expert VRyu uploaded two videos demonstrating how Makoto can use the upper body invincibility of her L Fukiage and kara-canceling to avoid the meaty frame of a 4-frame safe jump attack.
In the videos, VRyu uses L Fukiage, kara-canceled on its 1st start-up frame into L Karakusa (6234 LP~LK or 632146 LP~LK) to avoid 4-frame safe jumps from Ryu and Akuma.
This technique only works against 4-frame safe jumps. A 5-frame safe jump or a cross-up Air Tatsumaki from Ryu or Akuma would make the technique ineffective. Even in the case of 4-frame safe jumps, the attacker is of course recovered on frame 4, before the Karakusa completes start-up, so they aren’t entirely helpless.
This sort of technique can be applied to other characters as well. A few days ago Uryo mentioned his own test of the technique using Yun:
I heard from someone that in SSFIV if you kara cancel the first frame(?) of an invincible move into a different special move, you can perform that different special move while keeping the 1F invincibility. I tested it and it really is invincible. With Yun against Ryu’s safe jump from crouching HK, if you do L Nishokyaku kara-cancel → Zenpou Tenshin, Ryu gets caught in the command throw lol.