from what iv seen so far, in sp i can change shutter / aperture /zoom/focus.
from manual i can change shutter/aperture/zoom/focus
its sorta hard to tell a difference.
took more pics in class today.. will post em later..
When you take a photograph there are 3 main aspects that control it. ISO is one corner, Shutter Speed another, and last but not least Aperture. Think of these as a triangle. All of the angles must equal 180 degrees. If you change the values of any angle, you must equally change the values of 1 or both of the other angles to compensate.
Aperture is a measure of the
lens' diameter compared to the focal length. The pupils of your eye dilate to change their aperture. In the dark, your pupils will become larger to let in more light. When you step into the bright sun, they will close because there is more light than they need. Your own depth of field changes as this happens whether you are aware of it or not. Being a primary influence on depth of field, the value your lens' aperture is set to should be very importiant to you.
Shutter Speed is a measure of
time in seconds or fractions of a second, representing how long a photo is taken.
ISO speed determines how
sensitive your camera sensor is to the light which hits it. If the light entering the camera isn't enough to properly light the given scene, a high ISO speed will amplify the signal to make it brighter. Some information is lost in transition which shows up as noise, or speckles all over the image. Many “night vision” goggles work using equivalent methods.
In shutter priority, the camera will change the shutter speed as you click your selector wheel to the left or right. Because the shutter is open for a different amount of time, one of three things must happen:
A) change the aperture
B) change the ISO speed
C) do nothing and the brightness of the photo will change accordingly
Lets take a look at your baseball pictures which obviously change brightness as they go. The sun was relatively constant in the amount of light it provided so your camera must have done this on its own:
#1
Aperture:f/10
Shutter:1/30
ISO:100
#2
Aperture:f/20
Shutter:1/15
ISO:100
#3
Aperture:f/25
Shutter:1/15
ISO:100
One of the major focuses of this exercise is creatively controlling your aperture, and I bet you didn't even realize it was bouncing around from f/20 to f/25.
*Shutter priority uses the shutter speed you select and pics whatever value it wants for aperture.
*Aperture priority uses the aperture you select and pics whatever value it wants for the shutter speed.
*Full manual mode uses the shutter speed you select, the aperture you select, and the ISO you select. It doesn't make the big decisions for you. ISO is constant in the other two modes unless you have "auto ISO" selected. This grants you even less control. DSLRs are all about control. You should ween yourself out of the priority modes and into manual mode. Use the priority modes when the light is rapidly changing and it is hard to keep up with metering. Typically, the brightness in a scene is relatively constant and you can set the exposure and forget it. If you had used manual mode, your baseball pictures wouldn't have been different brightnesses.
So you can nudge the aperture in the general direction you want to go with shutter priority. You can also take off from a stop sign in 3rd gear because you don't want to accelerate too fast, but why *would* you? In fact, I recommend you stay away from shutter priority all together. Controlling DOF is an importiant subject and you should be conscious of it always. Aperture priority is, in my opinion, a much more practical medium. With static objects, such as your statue, the depth of field could play a huge role with the shutter speed really doesn't matter unless it is so low you are getting camera shake.
The only time shutter priority is better than aperture priority is if you want a
slow shutter speed. In your river scene you wanted very specific slow shutter speed to blend the water. This is the "video" effect where every drop that splashes over a rock is recorded like video and then blended together in one blurry frame. Shutter priority would be a good choice for that shot.
If you are taking a picture of a moving object and you want a
fast shutter speed, shutter priority is *not* the best choice. Think about it. If the widest possible aperture will produce the fastest possible shutter speed, select the widest possible aperture. You will get the fastest shutter speed every time.
Were you trying to focus on the dandelion? On those two sequences, my advice is to GET CLOSE! It strengthens the composition and emphasizes the subject. Keep trying- this is the best thing about digital! Just remember to always get close. 
