The 90D is a beast of a crop sensor, and you definitely need more than that tiny pop-up flash to do it justice. Ive spent plenty of time testing these on the 90D body specifically, and the tech specs really tell the story here. First, let look at the Canon Speedlite 430EX III-RT Flash. It is the safest bet for E-TTL accuracy. Since it uses Canons proprietary protocol, the communication is flawless. However, it runs on 4 AA batteries. At full power, you are looking at a recycle time of about 3.5 seconds, which is honestly way too slow for fast events. Youll find yourself waiting on the flash way too often. Regarding your third-party concerns, the 90D has the standard 5-pin hot shoe, so it doesnt have the sync issues found on the cheaper Rebel bodies. I highly recommend the Godox V860III-C TTL Li-ion Flash for Canon. The big selling point is the 7.2V/2600mAh lithium-ion battery. It provides a recycle time of 1.5 seconds at full power and lasts for about 450 full-power pops. Compared to the 430EX III-RT, the V860III gives you way more endurance for a long wedding or community event. If you want a softer fall-off for portraits, the Godox V1-C Round Head Flash is even better. It has the same battery tech as the V860III but the round head creates a more natural, circular light pattern. In my experience, the E-TTL on these newer Godox units is about 98% as consistent as native Canon gear. For the price and the battery speed, Godox is definitely the way to go tho.

Just catching up on this thread after work and honestly, I have a bit of a different take than the others. While I totally get why people love the lithium-ion batteries in the higher-end Godox stuff, I’ve always been a bit more cautious about them for casual event work. If you arent shooting every single weekend, those proprietary batteries can actually be a bit of a headache. If they sit empty too long, they can brick, and then you’re stuck buying a pricey replacement you can only get online. I really think the Godox TT685II-C TTL Flash for Canon is the smarter move for most 90D users. It gives you the exact same E-TTL accuracy and HSS support as the expensive models, but it runs on standard AA batteries. I personally use Panasonic Eneloop Pro AA High Capacity Ni-MH Pre-Charged Rechargeable Batteries and they are bulletproof. The recycle time is still very fast—barely a second or two—and if you ever run out of juice mid-event, you can literally buy replacements at a gas station or grocery store if you have to. Its also way cheaper, usually sitting around $130. That leaves you extra cash for a good modifier or even a second unit later on. Dealing with third-party gear can be scary, but the TT685II plays really nice with the 90D hot shoe metering. Just make sure the firmware is updated and you will be golden. Its a much safer bet for your wallet in the long run imo.

For technical reliability, the Godox V860III-C TTL Li-ion Flash for Canon wins on specs. The 7.2V 2600mAh battery provides 480 full-power flashes and supports HSS up to 1/8000s perfectly with the 90D.