This is a quick review of the Canon 90EX flashgun. I will not go into too much detail but just what it can do and why I bought it. I was a long time user of Canon EOS 650D which has built in wireless controller via the inbuilt flash. I do use it to control 1 x Yongnuo YN568EXII and 2 x Yongnuo YN565EX flash guns off camera. Recently I bought a Canon EOS 6D which lack a built in flash. That meant I had to use the Yongnuo YN568EXII as the wireless controller. This combination becomes much heavier than I like.
|90EX on Canon EOS 6D|
The 90EX flash gun was intended for the Canon EOS-M camera and it is the smallest Speedlite available. They are now appearing in the second hand market at very reasonable price. Mine was purchased used, but was in as new condition. The reason the 90EX was chosen over 270EX is because of the wireless flash control ability. The 270EX is much more powerful and it also has a tilting head, but lack wireless flash control.
|Speedlite menu in ETTL mode wireless enabled|
The power of the 90EX is about the same as the built in flash so it is not very powerful. High speed sync is also available on the 90EX. Do bare in mind it is not very powerful and HSS will reduce the power even more. It uses 2 x AAA batteries as power source. Physically, it only has an on/off button and a lock switch to lock the flash on the hot shoe.
|Speedlite menu in manual mode wireless enabled|
Overall, it is highly recommended for owners of Canon full frame cameras that do not have a built in flash. It is useful as a small fill flash and wireless flash controller but has limitation due to its small size and low power output. Other than that, there is no reason why any Canon crop sensor cameras would want to use the 90EX.