Hello and thank you for this assignment submission. Let me begin by answering your question regarding f stops.
Some lenses have different speeds. For example, the numbers on your lens may read
1.8, 2.8, 4, 5.6, 8, 11, 16, 22
or it could read
4, 5.6, 8, 11, 16, 22
Notice the numbers are roughly the same, but the one lens starts at 1.8 and the other starts at 4. The lenses that start at smaller f numbers are called “fast lenses”. The lower the number the “faster” the lens (even though it has nothing to do with shutter speed). The smaller the number on the lens, the larger the possible opening and therefore the more light that comes through. Also, as you know, the smaller the possible number, the shallower the depth of field.
A lens that starts at 1.8 will give you a great depth of field. It will almost be able to focus on the nose, while blurring the eyes. It can go really shallow. However, lenses that start at 4 will not have the same capabilities. On a similar note, the faster the lens, generally the more expensive it is.
With regards to your photographs: The rubber ducky image is great. It’s exactly what the assignment asked of you. You show movement in the ducks by using a slower shutter speed. Not only that, but you’ve used great color control in this photograph. You’ll learn about color simplicity in an upcoming lecture, but for now, just know that you’ve used great complimentary colors (yellow and blue), and these colors work very well together in photography.
Your first photograph however, doesn’t quite capture the power of depth of field. If you moved closer (really close) to your foreground you could have either made your foreground in focus or your background in focus. Get closer to your foreground and then set your focus manually you’ll be able to achieve a good depth of field even with your f/3.6 camera.