Distance to subject is important in photography. See at what distances you can shoot given a choice of lens parameters. Or modify distances to see how other lens numbers accommodate to it.
Distance from photo subject to camera along with focal length determines magnification of the subject.
With increasing distance subject will appear smaller on pictures given all other parameters equal the same way we see with our eyes. LensTutorial takes subject distance into account allowing you to see the actual size of your photographic model relative to the angle of view provided by current selected focal length. You can see how your model fits into the view cone of the lens depicted in green.
You can also see how increasing focal length magnifies the distant subject, by narrowing angle of view sufficient for a distant model to occupy full photographic frame.
Picture below demonstrates the effect. The rocks on the picture are roughly the same size, but distant ones appear smaller.
This feature helps answering very practical questions e.g.:
- What focal length do I need to make a head and shoulders portrait from 6 feet distance?
- Will I have a small enough DOF to blur the background?
- How far can I position my model given my standard out of the box camera zoom?
- My photographic mission includes photographing people in 10-ft room, which lens should I bring?