CFn-05-1 is geared for EOS -series film cameras .Do not set it if you have a. EOS DIGITAL camera or the E0S REBEL T2 / 300 _ If CFn-5-1 is set for such cameras, the flash control will not work properly The flash might not fire of it might fire only at full output

With Type-A cameras, if C.Fn-05-1 is set, wireless autoflash shooting will not be possible,

If "AF-assist beam 0FF" is set with the Speedlite or camera, the AF assist beam will not be emitted .

With Type-B cameras, even if .Fn-05-0 is sat, E-TTL II / E-TTL autoflash will not work,