Why can't I get a shallow depth of field (DOF) effect?

I am trying to get a shot of the subject that is a foot or two away from the background that I would like to have show as blurry.

This is what I am going after. Notice how the face of the dog is in focus and his rump is already very blurry. dog

This is what I get at max aperture of f/1.8 with my 35mm prime lens.

Note: The items behind my daughter are about 2 feet from her. My guess is the dog's tail is about the same distance from his face and is way more blurry. What am i missing?

I thought with an aperture of f/1.8 I would get a razor thin depth of field.

EDIT: Here is an image I took inches from my daughter and the bokeh is nice at the distance the TV is. I am about 10 inches from the subject and seem to get nice bokeh at about ten feet behind her (distance from her to the tv). I would love to be able to get that same bokeh at 1 foot behind her. Is that possible and what hardware would be needed?

Answer

I think the key difference here is subject distance. Depth of field is a function of aperture, subject distance, and focal length. The closer you are to your subject, the thinner your depth of field will be. That said, longer focal length is also a way to get the effect you are looking for as well.

If you have the option, using a wider lens with a wide aperture very close to your subjects will produce that very nice, very thin DoF and produce that dreamy, creamy background blur. However, if you do not have the option of getting in real close, a longer focal length will also produce that dreamy bokeh.

You mentioned you were using a 35mm f/1.8 prime lens for the shot of your daughter. Try using a 50mm f/1.8, or even an 85mm f/1.8. Each one will successively narrow your field of view, but in doing so, they will also "compress" the background. That is, make it appear as though it is closer to the primary subject, and increase the amount of visible blur in it as well. You will want to shoot at the same distance as with the 35mm, however doing so will shrink the scope of the scene. With a 50mm, you might only capture the blue part of the ladder, and exclude that fantastically giant "rubber ducky". At 85mm, you would probably narrow the scene down to just your daughter, and maybe a little bit of the ladder.

You can, obviously, also reduce your DoF by getting closer with the 35mm, and keeping your aperture wide open. You might not get as much blur, however you would keep more of the background in the scene.