关于佳能EOS7D相机在使用慢门拍摄时出现“Err 30”的问题

Err 30 报错应该是快门相关问题，和闪存卡、电池无关。
这是canon的错误代码对照表:
10 Malfunctions related to files have been detected.(*1)
20 Malfunctions related to the mechanical have been detected.
30 Malfunctions related to the shutter have been detected.
40 Malfunctions related to the power source have been detected.
50 Malfunctions related to the electric control have been detected.
70 Malfunctions related to images have been detected.
80 Malfunctions related to the electric control or images have been detected.
99 Malfunctions related to the mechanical charge mechanism have been detected.
*1: Err 10 is only displayed on the EOS-1Ds Mark III and other error numbers are shared.