Is buying a cheap alternative brand hot-shoe flash a great way to save hundreds of dollars or are you just wasting your money?

Let’s start with the key difference.

Cost

Nikon SB910 $538.81

Canon 580EX II $457.00

Pentax AF540FGZ $399.00

Yongnuo YN560 $67.40

So what are the similarities?

Power: The Yongnuo Flash has a guide number of 58. This means the camera has a similar maximum power to the other top end flashes listed above. (Guide Number indicates the power of the flash.  GN = max distance to subject x f-stop at ISO 100 – e.g. if GN is 58,  max distance to subject is 29 meters when aperture is  f/2 and ISO is 100.)

Manual Control: All four flashes allow you to manually control both the level of power and the zoom on the flash.

Slave Modes: All four flashes allow you to slave the flash so it fires when it detects the light from another flash.

Bounce: All four flashes allow you to both tilt and rotate the flash head to bounce the flash off the ceiling or walls

PC Sockets: Three flashes (not the Pentax) have a PC socket – particularly useful when using Pocket Wizards for manual off-camera flash.

Differences other than cost. The Yongnuo YN560 doesn’t have the following:

TTL Flash Metering (Auto Power Control): The cheap Yongnuo is all manual. You need to adjust the power rather than the camera sending out a pre-flash, measuring the amount of light that has returned and giving out a main flash that will give you what it assumes to be the correct amount of light.

Flash Compensation Control: The ability to increase and decrease the power of the flash when in TTL mode. (Similar to exposure compensation  when using in-camera metering)

Auto Zoom Control: The camera can tell the flash the focal length of the lens being used and therefore the angle of view. The flash automatically adjusts its zoom so that the spread of the light matches the angle of view.

High Speed Sync: High speed sync allows you to use flash at shutter speeds greater than the flash sync speed of the camera, useful when you want to shoot outdoors with a wide aperture.

Infrared Wireless Communication: The ability to communicate with off camera flashes using an on camera (or pop-up) flash. This allows you to use TTL flash metering when using off camera flash.

LED Display: A clear display on the back of the flash that shows mode, power settings, zoom settings.The Yongnuo displays all the information through a series of LED lights on the back of the camera. The row of orange lights is used to  indicate both zoom and power which can lead to confusion.

Build Quality and Reliability: The first time I used one of the YN560s it gave off a strange burning smell. I thought I’d fried it, but it has continued to work without any strange smells or problems since then. I doubt it has the same degree of weather sealing or ruggedness as the other flash units, but I’m not planning on a series of drop tests.

In summary, the more expensive flashes can do everything the cheap flashes can do plus various bells and whistles. The ability to use TTL metering is useful in some circumstances, but once you are using multiple flashes and radio triggers it is less useful or not even usable. The advanced infrared communication systems also have their place, but are less effective than radio triggers when using manual mode.

If you’re buying a single flash, have the money, and want the flexibility to shoot with TTL then get the matching flash from your camera’s manufacturer. If, however, you’re experimenting with off-camera flash and looking at getting a second or third flash then you could happily save yourself several hundred dollars by getting a couple of Yongnuo YN560s.