Achieving a blurred background using manual

[hashcake]

I’m starting to use my 450D more often in manual as I find this helps me try to get a better understanding of the different settings.
However, unlike with AV mode, I can’t seem to be able to get a blurred background.
Is this because ideally I need to use spot metering and also AE lock?

If I am barking up the wrong tree can someone please point me in the right direction?

 

[StewartR]

A blurred background requires (1) wide aperture (i.e low number like f/2.8) and (2) subject to be reasonable distance in front of background. That's it. Nothing to do with metering or exposure. If you set f/2.8 in Av or in Manual, you'll get the same result.

If you post a couple of your pictures (a successful one with Av and a failed one with Manual) we'll be able to tell you why it didn't work.

 

[Nicos Rex]

Just set the aperture as wide open as you need for your blurred background and then adjust the shutter speed for correct exposure - no different to AV but you have to set the shutter speed as well. You certainly don't need to use spot metering for every shot - just for the ones that you would need to anyway such as heavily backlit subjects.

The amount of light required for correct exposure has not magically changed just because you are in manual mode!

 

[hashcake]

A blurred background requires (1) wide aperture (i.e low number like f/2.8) and (2) subject to be reasonable distance in front of background. That's it. Nothing to do with metering or exposure. If you set f/2.8 in Av or in Manual, you'll get the same result.

Based on this I've just taken a couple of test shots im manual mode with a wider apreture and it's produced the results I wanted.
Easy when you know how!
Thanks Stewart, this isn't the first time you've answered one of my newbie questions.
You help is highly appreciated

 

[photon]

Reduce ISO and/or increase shutter speed so that you need your maximum aperture for the exposure you desire.

Preferably use a long, "fast" lens. Fast means it's got a large maximum (wide open) aperture e.g. f/2.8 for a zoom and most "primes" (fixed focal length lenses), though you can find f/1.8 and f/1.4 without looking too hard.

The background will be more out of focus the closer the subject is to you; the further away the background is; the wider the aperture you select; and the longer the focal length of the lens. The format of your camera also plays a part, but we'll ignore that aspect.

If you're shooting outdoors, leaves and the light shining through them form the visible "bokeh" (out of focus quality). The number of aperture blades and their shape influence the bokeh. With the lens off the camera and looking through it from the back, you want to see as near a circular aperture as possible at all the settings you intend using. The reviews of the recently released Sigma 50mm f/1.4 mention it having nine aperture blades.