Its best achieved with lens.
But you can also create an effect like that one with Adobe Photoshop.
The technique is called "Soft Focus" effect.
1. Open the image.
2. Duplicate the layer. (Ctrl + J) on Windows
3. Go to Filter -> Blur -> Gaussian Blur. Give the amount about 3 to 5. (This value depends on your image's focus, and resolution a lot, so please experiment with that values)
4. Then change the layer's blending mode to -> Soft Light.
(This is probably the most difficult to find, if you're new to Adobe Photoshop.)
i. You can go to Layer -> Layer Styles -> Blending Options...
ii. and change the Blending Mode from Normal to "Soft Light"(Also experiment with different blending modes, like "Multiply, Screen, Overlay, etc..." They have different effects.)