Even at 1/4 the cost of a mid-range Canon/Nikon speedlight, the KF590N still has many of the same features excluding high speed sync and master control. On-camera modes are TTL (any Nikon DSLR), manual, and multi (strobe). Off camera it has optical slave 1 & 2, and 2.4G RC Slave (with TTL, M, Multi). On camera it is compatible with Nikon. But off camera, it can be used as a wirelessly controlled slave by a Canon 580EXII, 600EX, and ST-E2. For Nikon, it can be controlled wirelessly by a SB-900/800/700, and SU-800 Master. Wireless modes include TTL, Manual, and Multi. There are 4 channels and 3 groups.The flash works well in all my tests. It's powerful, the light is evenly distributed with very little vignetting at wide angle, and its controls are easy to use. Included is a case, foot, omnidirectional diffuser, and manual. The case is good quality, and it has a velcro belt buck strap.▐ MODES- TTL: This setting is like the camera built in flash, it will try to get a proper exposure regardless of the cameras ISO and shutter speed. Has exposure compensation of 1/3, up to -/+3 stops.- MANUAL: Adjust the power from 1/128 - 1/1 in 1 stop increments using the horizontal buttons, and 1/3 increments using the vertical buttons.- S1: Flash fires when sensing another flash. This can be either triggered with on camera flash, or another off camera flash.- S2: Flash ignores a TTL pre flash, and fires on the second main flash.- SLAVE: Allows flash to be wirelessly controlled by a MASTER. This is done by first assigning the slave flashes to a channel (1-4) and group (A, B, C).▐ PROS:- TTL- Powerful.- Max 180mm zoom range.- LCD backlight (on/off).- Easy to adjust modes/settings.- 2.4G slave, Manual/TTL/zoom (canon or nikon).- Charge beep feedback to notify that it's ready to fire (on/off).- Thick batteries like Eneloop XX and Powerex IMEDION AAs fit fine.- Nice rubber clicky buttons.- Laser AF Assist beam (on/off).▐ CONS:- Slightly bulkier than most flashes.- Only 270' head rotation instead of 360', can't point it over my left shoulder.- LCD Viewing angle makes it hard to read when high on a stand.- Cannot be controlled by camera commander mode.- No battery level indicator.- No high speed sync.- No Master unit control.▐ CONTROLSThe controls are pretty easy to use, I figured them out myself.- Power button is hold/on off, takes about 1.5 seconds. Mode button cycles through modes.- Light/FN button: 1 press for backlit, hold press to enter the function menu where things like autopower-off, exposure bracketing, AF assist beam, and recycle beep can be adjusted.- Zoom button: 1 press selects zoom, adjusts using horizontal arrows. 2 press to select channel, 3 press to select group.- Arrow buttons - vertical arrows adjust EV comp, or 1/3 increments, horizontal arrows change power in 1stop increments.- Clear button - change slave modes ETTL, ITTL, S1, S2, multi. Press both clear buttons resets flash to factory default. Clear button 2 enables front curtain sync.Mode button: Changes between TTl, manual, multi.- Middle button: OK.Settings do not loupe, meaning you cannot go from 1/1 power to 1/128 without going all the way back down through the in between levels. Not a big deal, but I prefer loupe.▐ CONCLUSIONDespite its few cons such as being slightly bulky, the LCD not being very readable when on a light stand, and not having a full 360' swivel head, this is a good flash for under 100$.4.5 stars. Sample provided for testing and unbiased review.