Neewer (Godox) TT520 and TT560 flashes
I really, really wanted to love these flashes. Given the specs, and the price points, they were posed to become my new favorite flashes... as it stands, they're solidly in the 'good' department, because their specs aren't what is stated.
Specs: (TT560 in parentheses)
Zoom range: 35mm fixed
GN: 33 @ ISO 100 @ 105mm zoom (38) ----- this is not true in my tests 17 (20)
Full power to 1/128 in full steps
Trigger modes: Manual, S1, S2
Manual syncs via hotshoe for on camera, no ttl, or RF trigger (or PC for TT560)
S1 is standard optical trigger
S2 is optical trigger with pre-flash suppression
(External battery pack port for tt560)
4 second recharge (this is what they say, tho with NiMH / NiZN, much faster 2-2.5)
Supports 8fps shooting at 1/8 power or lower.
Power saving mode
Overheating shutdown (I will not be testing this. Though from what I've read, 10 full power shots, @ 2 sec recharge will trigger this mode, easily manageable, IMO)
Settings saved even after power shutdown.
Feels alright. These are not built for rough conditions, but still okay for everyday use. Controls are VERY nice and easy. Power is simply a toggle switch, no buttons to push, just left for on, right for off. On an ease-to-use basis, they're simple and easy.
This is where I fell out of love with these flashes. For $33 ($38) for GN33 (GN38 full manual controls, I wanted to love these flashes, and wanted to tell the world... but now no longer. I got 6 flashes to test, four TT520s and two TT560s.
The TT520s are rated at GN33... all four metered (with a Sekonic L358) to GN17 (f/5.6 @ 10') That's two full sops less than what they should be.
The TT560s are rated at GN38... both metered (with a Sekonic L358) to GN20 (f/5.6 5/10 @ 10') That's also two full sops less than what they should be. That's effing unacceptable.
I have attempted to contact Neewer / Godox many many many times over the past several weeks in regards to this discrepancy... no responses. This drops my opinion on them more than the discrepancy itself.
Slave and Sync
I've tested the PC, Optical, Optical with flash suppression and hotshoe syncs. Hotshoe works as you'd expect... I used them mainly with wireless receivers, no misfires over the past 5 shoots since getting them.
Optical slave mode works as intended, with good range. Indoors, no problems due to bounce, the flash triggered when hit with another flash anwhere in the room. Outdoors, with good aiming, 20-30 yards at full power triggered optically.
I tested S2 mode, optical with pre-flash suppression. The only flash I could test this with was my onboard flash from my Canon XSi. The onboard triggered the slave at 40 feet (across kitchen into living room) It also triggered at 45 degrees at the same distance, as well as 20 feet, fired in the opposite direction. Both optical modes are robust, and sensitive enough to be very useful.
Again... I wanted to love these flashes.... I still like them well enough, and at the prices they currently run ($34 and $40) it's not a bad start. I still like the YongNuo YN460II a bit better, but at $33 vs $50+ they do have their appeal, even when about 2 - 2.5 stops less powerful.
"Less powerful" though, is still good enough for many applications. For indoor shoots, boudoir, outdoor in late afternoon open shade... I'm more than happy with this power, just bump up ISO a bit to 400 if I want to shoot at f/8 or so.
My final test with these was to use them all in a beauty-ish shoot. One 560 in a 40" umbrellabox, another in a 20" softbox for clamshell, and three 520s, two in 20" softboxes for fill, rim, and one bare for hair light. It's an inexpensive way to get a ton of lights when tons of lights are wanted.
These flashes are solidly in my "decent" category. They're even more inexpensive than my recommended favorite budget speedlites, though less powerful as a tradeoff. They're still good enough for quite a few situations, though... Just need to know what your needs are, and how to determine if these will fulfil those needs.
I'll be using them regularly, for situations where I don't need much power, rim lighting, hair lighting, set lighting, and whatnot. For $34 they do make getting started in off camera lighting even easier. They're not fantastic, but in the tests I've done, they work reliably within their limitations.