What settings do i use to take a photo with subject in focus & purposly blurr the background

[altopiet]

What camera and lens do you use?

[altopiet]

Have a look at this Online Depth of Field Calculator it indicates out of focus areas in different circumstances, play around a bit with the settings...

[DogLover]

In a nutshell, you shoot at a large (numerically small) aperture.

[carrrlangas]

the longer the focal length; the shorter the distance to subject; the smaller the aperture value of your lens; and the larger the print size; the bigger the difference between the in focus and out of focus zones of your photograph.

Those in bold are the four variables for "depth of field". I´d also add ISO value since at high ISO, luminance noise will blur the difference between out of focus and in focus but it depends of the camera (newer ones have more usable high iso)

so, assuming you are using a DSLR with kit lens, set it at 55mm, wide open (f/5.6), get as close to your subject as possible while keeping compositional elements in the frame and make sure all your subject or, the important parts of it ar in focus (nose for example...) and Print / display it big.

[Kartynas]

An aperture with a smaller number (ie f1.4 to f4.0) will give you background blur, also known as a shallow depth of field. You have to be careful that you don't close down the depth of field so much that parts of your subject are blurry too.

A longer lens will give you a background blur effect too. If you only have a point and shoot or a DSLR with kit lenses, zoom out as far as you can on the camera/lens, and then move back to compose your image. You might need a tripod to reduce the possibility of camera shake depending on the camera model and how long the lens is.

[Na Horuk]

So, set your camera to Av mode and choose the lowest f-number possible. If you want a lens with a really low f-number for a good price, look for the DA 50mm f1.8.
The other thing is, how near you focus. If your subject is close to you, then the blur will be more noticeable than it would be if you are focusing near infinity.
The third thing is, using a lens with a long focal length (high mm number). longer focal length lenses will give you a thinner Depth of Field and a more noticeable blur at low f-stops.

[Adam]

What settings do i use to take a photo with subject in focus & purposly blurr the background

You might find this video tutorial helpful:
Beginner Portrait Lens Guide - Gear Guides - PF Blog