Here is a quick tip about depth of field. This photo that I took in Colorado was at the F stop 5.6 Most people just say F5.6. You will probably notice how blurred everything else is except the head. This is because of the depth of field F5.6 creates. Especially at 300mm. The LOWER the f stop number is, the higher your shutter speed is and the shallower your depth of field is. The HIGHER your F stop number the lower your shutter speed is and more things will be in focus. When it is a higher number like F8 the depth of field will not be so shallow. More things will be in focus. Many landscape photographers use high F stops like F22 or higher because it gets the whole landscape in focus. But for wildlife photography, it is usually best to shoot with as low of an f stop as possible. Because it increases the quality of the photo and makes the subject stand out more. If this lizard photo had been taken at F 8 or higher, I probably wouldn't like it so much. Because usually when more is in focus, the more boring the photo is. This is a principle of bird photography, I do not speak for other forms of photography. Although this a is a pretty general rule.
Posted by John Mark Simmons