After a few comments on a previous post, I figure I probably should give a better idea what the difference between hard and soft light. This is a VERY key concept as a photographer in creating images: knowing the difference between soft and hard light, how to create the light you need, and controlling the light once you do create it.
First, hard light is something that is created from a small point source of light. That isn’t helpful, is it? Think of it this way: when you look at the shadows cast by a small, point source of light, the shadows will be crisp and well defined and very black. Examples of small point sources of light include the Sun and any battery powered flash you purchase. Frequently people will call hard light “contrasty”. Soft light, on the other hand, is more grey types of shadows, if any, and the lines are really blurry. It is created from large sources of light – think umbrellas that are close up, softboxes, and parabolic umbrellas. The thing they have in common is that they either shoot a small source through a material that difuses the light, or they bounce a small light to defuses the light. In both cases, they make the light source bigger. The more difused or soft the light (or more diffusion layers), the more light you will lose with the modifier. You need to now go through the various light modifiers you have and determine which they create.
Ok, two things are taken care of. We have one last one to deal with: controlling the light once created. This is really the easy but also hard part. You do this by feathering your light source on you subject. You what? That is what I said, you feather. This is taking the light source and using its edge to create the light you want. If you shoot the light and point it from the center, usually the center will be hotter and then it fades away from that as you get further out. What gives you more flexibility is to use the edges of the light. If you are using grids of any kind, there is no ability to feather your light. Also, the softer the light source, the more feathering you have because of the broader through of light. You want to use only the side of the light modifier – not the full throw of the light. Now, play with the different modifiers and see what you can do to control the light.
There you have it. Soft and hard light, modifying the light, and how to use it. Play with your modifiers and try some things out, see how the work, and be ambitious. The more you play and learn about your light modifiers, the better you will be at photography.