Maximum pixel size for photos added to Iphone 4/4S?

Hi.
I want to add photos to my Iphone 4S that can also be zoomed in on.
I'm guessing it's about twice the screen resolution?

Does anyone know what is the exact maximum pixel size supported?

I did several searches but can't find a definitive answer.
I know how to re-size images etc so that not an issue.

Thanks

Thanks, I'll test that.Just got first Iphone yesterday (4S)
I thought maybe Itunes "optimised" images during being sent to the iphone during sync, so that might be a process the files created on the phone get put through?

Just tested it....

I tested a image , one sized to 2000pixel width , then a bigger version of it sized to 3264 pixel width.

At the maximum zoom by pinching the screen both images zoom up to exactly the same size... so it appears there is some sort of viewing limit

It's possible the that even though the camera takes images of a certain the viewing limit is restricted...

Any thoughts?