Originally posted by deiberson but what will i have to do when i want to keep the entire shot in focus
I suggest you read oup on the basics of exposure: aperture, shutter speed, and iso. Google those terms together, and you should find plenty of references that will give the answer to this and all other similar questions. Many people recommend the book "Understanding Exposure" by Bryan Peterson, but really, any basic bookon photography should explain this.
The short answer here is, to get more depth of field (the term for how much is in focus) you need a smaller aperture (which means a larger f-number). In Av mode, you'd turn the wheel until the aperture reads at least f/8. chances are you'll never get the *whole* room in focus.
Quote: i'm using that f1:1.4 lens, turned the aperture ring to "A", went to custom settings and did this (tell me if i'm correct):
If you're lens has an "A" position, leave it there and never move it. And in that case, the custom option you mention has no effect. It's not harmful, and you might as well set it now so you'll be ready it in the event you also use a manual lens "without* an "A" position. But that's the time time you need that option set to allow you to take pictures using lenses with aperture rings that are *not* set in the "A" position.