My 580EX II only exposes correctly in bounce mode :-0

[W13]

I noticed that my speedlight underexposes (by at least 2 stops) in the normal flash head configuration.  Once I place any kind of an upward bounce on the strobe, I get a correct exposure.  It exposes correctly in the left/right bounce configuration.   It also underexposes in the 7 degree down position as well.  I noticed this when I had an external battery source attached to flash.  I disconnected it and the flash was still underexposed with fresh batteries.  I did a "reset settings"  on the camera and it still did not fix the problem.  😕

Any thoughts?

[Skirball]

Can you post an example?  That doesn't make sense at all.  Is there an obvious subject in front of the camera?

[TCampbell]

You may have a problem with your lens. Do you have an alternate lens that you can use to test this?

If (and only if) the speedlite is mounted on the camera and also pointed straight ahead (no bounce up or left/right) then the E-TTL II system will take the lens' reported focus distance and use that to set the flash power. If the flash is not straight-ahead OR not mounted on the camera, then the E-TTL II system knows that it can't use the lens' reported focus distance and will set flash power based only on the amount of light returned in the pre-flash check.

Not all lenses report a focus distance and of course 3rd party lenses have to reverse-engineer everything. But since you've pinned this problem down to the ONLY case in which the camera will use a lens' reported focus-distance to set the flash power, I'm guessing this has more to do with the lens than the flash or camera body.

If you have a different lens, I would test this and let us know what you find.

[W13]

Thank you for your reply.  Interesting observation that I will keep in mind.  

I called Canon and "solved" the problem.  I put solved in quotes because I still don't know what caused the problem.  Prior to posting and calling Canon I reset the camera settings and that did not help. When I called Canon and told the tech of the problem, he was scratching his head too.  Then he asked me if I reset the speedlight.  I told him no, because I didn't think there was anything to reset, but just to humor him, I  reset the flashhead.  I have no idea what that did (it did not reset any custom functions, nor change settings on the display that I could see), but after the "reset", my speedlight worked fine.  I would like to say that I had it on some whacky setting, but it's funny how no one could diagnose the problem.  The only other cause that I could think of was a faulty speedlight in which a reset fixed.  I'll be keeping an ey on it to see if the probelem replicates in the future.

If anyone out there needs to reset their speedlight, go into the menu and select: "external speedlight control" and then push the "set" button, bringing up the next menu.  Select: "flash function settings."  This will bring you into another menu with "flash mode" as a defaulted selection (however, any one of those selections in that menu will work) Push in the "info" button on the camera and you will get a "Clear all Speedlight settings" prompt.  click "ok."  

[JerseyTom]

Tim, what about the Canon OC-E3 Off Camera Shoe Cord. Specs say it maintains all on-camera flash functions including E-TTL / E-TTL II for one Canon Speedlite used off-camera at distances up to 2'.?

[TCampbell]

Part of the point of the E-TTL off-camera cord is to allow the flash to be mounted on a flash-bracket. The flash should behave as if it's still on-camera. I haven't tested this.