Camera Settings when using 580EX

By no means am I an expert with cameras and I do miss alot of details when it comes to assessing what settings I will be best using but when using my 580EX II on my 1D classic on automatic I notice the settings will give me alot of the same results. I put my flash on and put the camera into 'P' mode. It gave me a 60 shutter speed and a 4.0 apperture. I took my photo and everything looked fine. I then set the camera to 'Av' and put my ISO to 4.0 and it told me I needed like 1.3 as my shutter speed which gave me the same kinda result. I then set the camera to 'M' I put the apperture to 11 and shutter speed to 120 and my result again was pretty much the same. My question is why when using Av does my shutter speed think it needs to be so long. Ideally I want to use a quick shutter speed and use whatever apperture I want to. I figured that is possible as I am using a fairly decent flash as you know.

Anyway, just a bit of knowledge would be great. I love to learn so I would love to find out what the camera is doing etc.

towersinthesky wrote in post #6139273
By no means am I an expert with cameras and I do miss alot of details when it comes to assessing what settings I will be best using but when using my 580EX II on my 1D classic on automatic I notice the settings will give me alot of the same results. I put my flash on and put the camera into 'P' mode. It gave me a 60 shutter speed and a 4.0 apperture. I took my photo and everything looked fine. I then set the camera to 'Av' and put my ISO to 4.0 and it told me I needed like 1.3 as my shutter speed which gave me the same kinda result. I then set the camera to 'M' I put the apperture to 11 and shutter speed to 120 and my result again was pretty much the same. My question is why when using Av does my shutter speed think it needs to be so long. Ideally I want to use a quick shutter speed and use whatever apperture I want to. I figured that is possible as I am using a fairly decent flash as you know.

Anyway, just a bit of knowledge would be great. I love to learn so I would love to find out what the camera is doing etc.

Because in Av mode your camera is still metering for a correct exposure using ambient light and just using the flash as fill in.

In Av, your camera is metering for the ambient light -- your flash being on your camera has no bearing.

Set your camera to Manual -- set shutter speed to 1/250 or slower, set the aperture to what you prefer and let the flash do all the work. If shooting in bright sunlight, you'll need ISO 100 and around f/10 or higher.

With flash, shutter speed is not important for stopping the action -- it's the flash firing at 1/2500 of a second or faster to do the "freezing".

Do a search, there are gobs of posts concerning flash photography on here.

thanks very much for the quick reply. I didn't know if it was something like this but this makes it alot clearer! thanks!