The Canon 540EZ is a high-powered flash unit from the EOS film SLR era, aimed at "professionals/advanced users." It's a legendary model boasting a powerful guide number of 54 (ISO100・m) and auto zoom. While it doesn't support TTL with modern digital EOS cameras, it's still perfectly usable as a manual flash. ◎ Detailed Explanation of the Canon 540EZ Flash 〇 Basic Specifications - Guide Number: 54 (ISO100・m) → Very powerful, befitting a high-end model of its time. - Compatibility: Exclusively for EOS film AF cameras → Not compatible with E-TTL / E-TTL II on digital EOS (TTL not supported). - Power Source: AA batteries x4 → Easy to use with readily available batteries. - Auto Zoom Function → Automatically adjusts the illumination angle according to the lens focal length. - Hot Shoe Connection → Can be mounted on a standard hot shoe. 〇 Main Functions ✔ TTL (for film EOS) - TTL automatic flash control is possible with film EOS cameras. - Since TTL does not work on digital EOS, it is used exclusively for manual flash. ✔ Manual Flash - Output can be adjusted in stages. - When used with digital cameras, operation is basically manual exposure + manual flash. ✔ Auto Zoom - Automatically adjusts to an illumination angle equivalent to 24-105mm. ✔ Multi-Flash Photography Function - Supports multi-flash photography using multiple 540EZ units. ◎ Usability and Evaluation 〇 Pros - High light output and excellent cost performance (low used price) - Easy to use with AA batteries - Perfectly practical as a manual flash - Durable and highly reliable △ Points to Note - TTL cannot be used with digital EOS (important) - Older model, so charging time is relatively long - Does not have modern features like wireless E-TTL ◎ Points to Consider When Using with Digital EOS - Manual flash only - Determine exposure on the camera side in M mode - Adjust the flash output from 1/1 to 1/128, etc. - Since the light output is strong, using a diffuser or bounce flash is effective ◎ Condition ・【Fully functional】All functions work perfectly with EOS film AF cameras. ・There is a "crack" in the diffuser, but it does not affect use.