In recent years, the photography market has been changed dramatically by the emergence of compact system cameras. These picture-taking devices have interchangeable lenses but are made much smaller than SLR cameras by dispensing with the bulky mirror box and viewfinder.
Advances in sensor technology and a growing population of “prosumers” mean that many of these cameras have advanced controls and performance comparable to even a mid-range DSLR. But then we have a problem. What if you want to use an external flashgun on top of your mirrorless camera? According to this mirrorless camera guide, the flagship speedlights of Nikon and Canon, such as the SB-910 and 600EX, are far too big, heavy and bloated with features, most of which you can’t even use. Even with a TTL cord, it seems silly to carry around a system flash that’s bigger than your camera.
Perhaps you even already have one of these flashes for your DSLR, but just want something you can casually slip into your pocket for days out with your compact system camera. You don’t want to break the bank since you might only use it occasionally, but it needs to be better than the pop-up flash you have.
Enter the Changyin CY-20, made by Yin Yan. As the name suggests, it’s from China. It costs less than $15. Yes, $15. Including postage. You can get it in the UK for £15. 
So, what does this not-particularly-substantial sum of money get you? Gadget geeks might want to look away now. 
The CY-20 has just two modes: On and Off. I like the first one best. There is no TTL, no autofocus-assist lamp and no fine power adjustment. What looks like light sensor on the front is purely decorative. Yes, the new Fujifilm EF-X20 has much more control, but costs just a little bit more. Yinyan want to cater to people on a tighter budget. 
You do get a handy calculator on the back to guesstimate your exposures. And a test button. There’s also a 2.5mm sync port if your camera or triggers don’t have a hotshoe.
Fortunately the triggering voltage is very low so your radio remotes and camera are safe. 
The device takes just two AAs and has no facility for external battery packs. The recycle time is best described as “it’s ready when it’s ready”, but the manufacturer says it’s seven seconds. However, you can dump the power at any stage during charging, even when it’s switched off (definitely a feature) so if you were really clever you could take a picture partway through recycling to get 1/2 and 1/4 power. 
While you can’t swivel the CY-20, you can tilt it, all the way up to vertical, 90°. This is one of the best features, allowing you to bounce flash from the ceiling, or the wall if taking a portrait. Every little helps on the cameras with the smaller sensors, sometimes derided for their low light performance. Here is the CY-20 sitting happily on what is probably the smallest mirrorless camera of them all, the Pentax Q. The Q can fit on a keyring and is absolutely pocketable, even with the lens attached. There’s probably a fair bit of empty space inside the CY-20 because it feels very light in the hand and doesn’t make your system too top-heavy. In fact, it feels quite natural, and can happily disappear into a jacket pocket. 
You’ll recall that we don’t have TTL here. However, if you want it, you can still get it in the same shell from Metz with TTL for Nikon, Canon, Olympus, Panasonic, Pentax, Sony or Leica. It’s then called the Mecablitz 24 AF-1 and costs a little bit (well, a lot) more but you’re getting more for it. 
I’ve personally found that bouncing off the ceiling I can find the right exposure and keep my camera in one setting all evening without having to make adjustments. If you do need to, it’s easy to change any combination of your distance to subject, aperture, Iso sensitivity and flash tilt.
At full power all the time, the Yinyan CY-20 is pretty bright. The guide number (GN) for direct flash is 20 (metres). Turn your Iso and aperture down a bit if you don’t want to nuke your subjects. In a pinch, cover half the fresnel with your hand and you have 1/2 power! The light it emits has also got a bit of a magenta tinge to it, so customise your white balance to taste or put your camera into Auto-WB mode.
If you want much much less light (i.e. none at all in the visible spectrum) then look out for the CY-20S, which is the same unit but has an infrared filter over the lens so you can use it as a master for your optically-slaved remote flashes.
Where to buy
The Yin Yan Changyin CY-20 is available online for under US$15 shipped from China or Hong Kong, or from UK resellers for £15. In Germany you can find it for around €20-30.
What do you use with your mirrorless camera? Let us know in the comments below.