40D - Focus assist flash fires away and sometimes no shot

Hi, I am not a fan of the flash unit on the 40D and steer away from using it. The problem is that when I do need it for a quick snap, for some reason I find that it fires away profusely as the camera wants to focus. Now and then the 40D just refuses to take the shot, because the AF is not happy. You release the trigger and try again and hope for the best. In so doing you miss the moment and it is not captured.

Has anybody else noticed this behaviour?

In your custom settings (III-5) you can turn off Focus assist and set it to Off Camera Flash or Off. If it's refusing to take the shot, you are probably not in focus, and in the view finder is the little green dot (focus confirmation) blinking or solid?

It is definitely not in focus and the green dot blinks to indiacte that as well. I just find it irritating that all this technology is supposed to help and then it lets you down. The point is that it may highlight a general AF issue with the body.

Another example of just how Utopia and photography doesn't always fit in the same sentence I'm afraid. Just because your flash is emitting the focus assist beam doesn't mean the camera will be necessarily be able to achieve focus. What focus point are you using? How far away from your subject are you? How contrasty is your subject? ..............the list goes on

gofer wrote in post #6604709
Another example of just how Utopia and photography doesn't always fit in the same sentence I'm afraid. Just because your flash is emitting the focus assist beam doesn't mean the camera will be necessarily be able to achieve focus. What focus point are you using? How far away from your subject are you? How contrasty is your subject? ..............the list goes on

Yes, the list is long and I must add in defense of the 40D, that this normally happens with lower contrast and off-center focus points. Just learned about the more accurate center point and will re-test the camera's ability Distance not far, 3 to 4 meters.

David Ransley wrote in post #6604731
Yes, the list is long and I must add in defense of the 40D, that this normally happens with lower contrast and off-center focus points. Just learned about the more accurate center point and will re-test the camera's ability Distance not far, 3 to 4 meters.

Your quoted distance of 3 to 4 metres may not seem far but at 4 metres when using the pop up flash you'll certainly be just about at the limit of the focus assist beam range - even in ideal conditions.

gofer wrote in post #6604806
Your quoted distance of 3 to 4 metres may not seem far but at 4 metres when using the pop up flash you'll certainly be just about at the limit of the focus assist beam range - even in ideal conditions.

Agreed, I checked the flash guide number the other day and it is about the max you can go.