Big problem with Canon 50mm 1.8 ! please help!

[Ofirfir26]

I have a Canon EOS 550D / T2i, and I just got a canon 50mm 1.8 lens yesterday ,
and I have a couple of huge problems .
What I see in the screen when I want to take a picture (on any mode except for video) is great! The background and bokeh look amazing , but when I take the picture everything changes , the background isn't as blurry and the bokeh isn't very good.
(And that's when I use manual focus and I don't change the aperture or shutter speed or iso, nothing , i'm on the 'no flash' mode ).
see pictures:
1. What I see before I click and shoot :


2. What the picture that comes out looks like :


Now , the outcome of the picture is bad , but when I take videos it's even worse ! It's as if the focus range is really small and I can't get blurry and bokeh-i videos :


Pleae tell me if I can fix this , or is this how it's supposed to be? because I got really disappointed

Thanks a lot !
Ofir

[Skirball]

I don't use Liveview, so someone can jump in if I'm wrong, but I'm assuming it'll function the same way as looking through the viewfinder (I know it does an exposure simualtion, but I don't think it actuates the aperture).

When looking at an SLR camera to compose a shot the camera keeps the lens wide open to allow in as much light as possible so you can see and autofocus..   This will also have the smallest depth of field, so backgrounds will be more blurry.  Only when you push the shutter does the aperture momentarily close to your select aperture, which in this case is f/7.1, which is stopped down quite a bit.  If you want to get what you see in the preview then select your aperture of 1.8.

Also, there is a little button on the camera body around where the lens connects (I think it’s lower left on a Rebel?).  It’s called Depth of Field preview, and it will actuate the aperture so you can see what it’ll look like (though the exposure will be off).

[PLee]

Just make sure you're focusing on something very close to you with an open aperture (small f-number) and the background should blur out for you. You're using f/7.1 in that first shot. Keep it simple and try f/1.8 with your lens to start.

[ebiggs1]

This is one of the failures of an automatic mode. Change the setting to Av. Set it to f1.8 or f2 and try again.

1/400 at f7 with ISO 100 is going to get you pretty sharp DOF.

Sometimes light situations do not permit the correct settings for what you want and that is where ND (neutral density) filters are used.