Honestly, it's a bit disappointing that the monitor market under 500 bucks is such a minefield right now. I've had issues with almost every budget screen failing at the worst possible moment. The Ninja is such a power hog and carrying extra batteries for it is a literal pain in the neck... it just feels like we're always compromising something. Before I give you a final recommendation tho, are you planning to use a full cage or just mounting it straight to the hot shoe? If you're going handheld all day in San Diego, the weight balance is gonna be way more important than you think. If you want something that actually handles the sun without being a total brick, look at these:

• Desview R6 UHB 5.5 Inch 2800nits Touchscreen Monitor
• Shimbol M5 5.5 Inch 2000nits Camera Monitor The Desview is bright enough to melt your eyeballs but the build quality is kinda meh so you gotta be careful with it. The Shimbol is a bit more robust and doesn't mess with the Sony colors as much as those cheap panels do. Just a heads up, these ultra-bright screens get hot. Like, really hot. I've had screens dim themselves to protect the hardware when shooting outdoors, which is just... not great. Budget for some high-quality Sony NP-F970 Rechargeable Battery Pack units too, because high nits will drain a small battery in like 40 minutes. It's an extra expense but way better than a dead screen during the first kiss.

For a wedding, you definitely need reliability over flashy features. I have used both and the Atomos Ninja V 5 inch 4K HDMI Monitor is a decent option for an A7SIII. It is built better than the Portkeys and the OS is stable, though the Portkeys is brighter for outdoor work. Couple of quick tips for your shoot:

• Skip the cheap cables and get a Zilr 4K HDMI 2.0 Cable 45cm because a bad connection will kill your focus peaking right when you need it.
• The Ninja gets hot so dont block the vents, but the fan noise is basically a non-issue unless you have a mic sitting right on top of it. Stick with the Ninja if you want peace of mind... nothing worse than a screen glitching out during the vows.

To add to the point above about the budget minefield, the core issue is usually the HDMI controller quality and thermal throttling. When you're running an A7SIII at high bitrates, some of those cheaper monitors drop frames or exhibit significant input lag because their internal processors cant keep up with the metadata overhead. Since you're worried about reliability and brightness for that San Diego sun, I'd suggest looking at the SmallHD Action 5 Monitor. It hits 2000 nits and uses a hardware platform designed for low-latency monitoring. It lacks the power-hungry recording features of the Ninja, which is actually a benefit here because it stays cooler and wont kill your batteries halfway through the ceremony. If you can handle a slightly larger screen for your rig, the Osee G7 7 inch 3000nits Ultra Bright Monitor is a total workhorse for the price. It is incredibly bright for outdoor use and the OS handles Sony's log profiles much better than the entry-level brands. Focus peaking on these units is just more surgical and precise, which is vital when you're shooting wide open at a wedding and need to be 100% sure the eyes are in focus.

Re: "For a wedding, you definitely need reliability over..."

• Honestly, reliability is exactly where I have been let down so many times. I used to be all about the flashy features but after years of doing weddings, I have learned the hard way. I actually tried using that Portkeys LH5P II 5.5 Inch 2200nit Touchscreen Monitor for a summer beach ceremony last year and the wireless control was such a headache. It kept disconnecting right when I needed to toggle settings, which is super stressful when you only get one shot at the processional. Tbh, the build quality felt like a plastic toy and it got so hot I thought it was gonna melt. Even the Atomos Ninja V 5 4K HDMI Recording Monitor has been a bit of a letdown lately. The fan noise is 100% a real issue. I had one on a cage right next to my mic and you could definitely hear that whirring in the quiet moments during the vows. Not as good as I expected for something everyone calls the gold standard. Plus, the colors on most of these mid-range screens never quite match what the Sony sensor is actually seeing, which makes pulling manual focus really tricky if your peaking is off. It is just frustrating when you spend that much and it still feels like a compromise. I gotta ask though, what is your plan for power? Are you rigging this onto a gimbal or just going handheld? Those high brightness screens are absolute battery hogs and they add a ton of weight you might not be ready for during a 10-hour day.

Just found this thread. Tbh if you're worried about that San Diego sun and need to stay under 500 bucks, you should look at the Osee T5+ 5.5 Inch 1000nits Camera Monitor. If you can handle a slightly bigger footprint, the Osee T7 7-Inch 3000nits High Bright Monitor is a beast for outdoor visibility and usually sits around 250 to 300 dollars. The technical reason I like Osee for Sony setups is the UI. It basically clones the SmallHD PageOS workflow. You can swipe between different toolsets, like having a dedicated focus peaking page and an exposure page with your waveform. It makes life way easier when you're rushing during a wedding ceremony and dont have time to menu dive. Check out sites like Newsshooter or CineD for their technical lab tests on these screens. Most budget panels lean green or magenta but Osee supports custom 3D LUTs so you can calibrate the preview better. Ngl its a solid middle ground between the cheap Feelworld stuff and a pricey Ninja. Just make sure you have plenty of Sony NP-F970 Rechargeable Lithium-Ion Battery because pushing 3000 nits will chew through power fast... it sucks to have a monitor die during the vows.