01-27-2016 12:39 PM - edited 01-27-2016 12:40 PM
If you look at your 40D menu under the 2nd (middle) yellow wrench you will find 'Flash control'.
Upon selecting that you will notice there is a menu choice for Built-in flash func. setting and one for External flas func. setting as well as External flash C.Fn setting.
Those External flash setting menu choices are what is needed by the 90EX and the 270EX, since they have no way of changing those settings on the flash itself.
Those menu choices are missing from your classic 5D and the 30D and are why they don't work with the 90EX and the 270EX.
And the difference between the 430EX and the 430EX II and the 580EX and the 580EX II is that the II versions of those flashes can be controlled by either with their on flash controls or the in camera menus. Where the original versions of those flashes can only be controlled with the on flash controls.
01-27-2016 01:13 PM
01-29-2016 07:23 AM
Thanks. I am aware of the flash settings on newer cameras (including 40D - I mean newer than 5D and 30D)
These 2 flashes work well on 5D and 30D except that they are not fully compatible - cannot perform the AF assist beam. Menu choices are not missing but just cameras/flashes compatibility problem. 5D does have the menu and the camera has no built-in flash so it is definitely for external flash. When 05 is enabled or set to emits, AF assist beam is not fired.
The 90EX doesn't have focus assist strobe on any camera, and the specifications listed on the Canon website for the 270EX shows it doesn't have focus assist strobe on those cameras. So everything is working normally.
01-29-2016 03:31 PM