[lisaly]

All of this information is wonderful, and as you use your camera more, it will become more like second nature to you. You are posting some wonderful images of your beautiful babies. I am envjoying them a great deal.

Each lens that you us is a little dfferent, and the depth of field and amount that is able to be in focus when the lens is wide open varies. The 35mm lens is considered a mild wide angle lens, but on a DX camera, with the 1.5x crop, it is like a normal lens. A normal lens equals the focal length that our eyes view things at. It is a wonderful lens to have. With wider angle lenses, more parts of a photograph will be in focus at a given aperture than if you were using a telephoto lens. Still, you are moving in closer when you take the photos to compensate for the wider angle of view, and then you are losing a little depth of field. With more practice, you will see how focal length of a lens and aperture affect the depth of field in a photograph. With an ultrawide lens, there's almost no need to focus, because so much of a photo will be in focus, even with the lens fairly wide open.

Your picture of your two babies is wonderful! You used a wide aperture and a fast shutter speed, which completely stopped the action. Because the lens brought a lot of light into it due to it being wide open and the fact that it was bright and sunny, the camera was able to have a high shutter speed. That made it able to stop the action. I do adjust ISO to achieve the effects that I want also.

I highly recommend buying buying the book Understanding Exposure by Brian Petersen. He explains things so clearly, and his images are wonderful. I have a number of his books. They are fast to read, and you can pick them up for just a few minutes and get so much out of them. This is his most popular book. I think it is a must read for anyone interested in photography, and it is very popular.
Amazon.com: Understanding Exposure: How to Shoot... Another good book that he has that is like a combination of all of his books abridged is his Field Guide, the newest of his books:
Amazon.com: Bryan Peterson's Understanding...
Bryan also has online courses. I haven't taken any of them, but I've heard very good things about them. It is through his Perfect Picture School of Photography. There are many wonderful courses (one also on taking great Pet Photographs), and I am very interested in taking his Portraits Unplugged course. Here is the link for his most popular class:
Understanding Exposure
Understanding Exposure