Do you know this effect on instagram where you make everything blurry except the subject. Well this is the real way to do it. You can do that by holding your lens in front of your DSLR, and tilt it a bit. its a little hard at the beginning but after some practice you can get awesome results. I learned this technique here. it's all explained there. But with a Sony alpha DSLR you have some troubles, at first the shutter is locked and at second the aperature of the lens will shut to its smallest when you detached the lens. And you don't want that. The shutter problem can be solved by setting the camera on manual mode, and the newer cameras have an option for it in the menu. For the lens problem I have two solutions. To see them click 'like to see more?' under the post. The second solution is also nice for non-Sony users
pull back that lever.
For a lot of lenses the aperture is set mechanical. If you detach your lens you can see a little leaver at the back, if you pull that back your aperture will open. If you put something for it it can't close anymore and your aperature will be open again. make shure the thing you use is removable. As far as I know Nikon, Sony and Pentax lenses have this system, but I'm sure there are more
an other lens
When using different types of lenses you'll notice that lenses with greater focal lengths (more mm) are better when you want to take photos of things a little further away. And wide angle lenses are better for closeups. It's the world upside down! It really takes some practice but the results are so fun.