Thursday, October 2, 2008

Digital Photography Tip #002 - Aperture Priority.

Tip #2 already! I had a thought and needed to express it. I may post lots of these in a relatively short period of time until I catch up to myself. So here we go with #2.

Aperture Priority Mode.

Who is in charge of how your photo is being recorded? You or your camera? If you are running in any of the "creative" modes or Full Auto, then it is your camera. Running on P mode is better but not really. I'm using Canon's modes here so on a different camera they may be called something else but they do the same thing, take control away from you.

Now don't get me wrong, my Rebel XTI takes some great pictures on full automatic but they do not stand out. The camera will decide how to expose the scene for you. If you have lots of bright white or lots of darks look out. The camera wants to make the whole scene an 18% grey. And that is what your pictures will look like, grey, washed out, blah looking.

Switch over to one of the manual modes. Av (aperture priority), Tv (shutter priority) or M (full manual). They will give you the control you need over your photos.

Av or Aperture Priority will allow you to set the aperture of the lens. Why would you do that you ask. Well with control over your aperture, you have control over your Depth of Field (DOF) and your exposure. Sure your camera will pick a shutter speed that it thinks will give you the best exposure and that may not be what you think is the best but we will get to compensating for that later. Mostly, you get control over your DOF. Have a look at these examples.


IMG_8307
This is a photo I took this past summer where I used a closed down aperture of f/22. The larger the number, the smaller the aperture the more depth of field you have. Note how everything from the bale in the front to the treeline at the back are in focus. Now this was taken at 37mm and wide angle lenses do give a greater depth of field to begin with but you get my point, smaller aperture = greater DOF.

Unit 2 Photo 1
This one on the other hand was taken with a wide aperture of f/5. Note how the cat tail in the foreground is in focus but the background is blured effectively separating the subject from the background. This was taken at 135mm. Telephoto lenses and long zoom lenses have less DOF to start with but you see my point here. Large aperture = less DOF.

I live in this mode most of the time. I want the control over the DOF most of the time. Sometimes, I want control over the shutter speed. Why? Well that will have to wait for next time.

Chris.

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