Alright let's talk about aperture priority mode on the Canon 40D. This is one of the creative zone modes that is available on your dial, on your mode dial over here. On the top of the camera on the left side if you turn the dial, right now we're in shutter priority mode or T.V. mode and what we're going to do is turn the dial clockwise and now we're set to aperture priority mode which is indicated by upper case A lower case v, right next to a white marking on the top of the body there. This mode basically allows the user control of the aperture in order to maintain a depth of field that is appropriate for the subject and what, what it does is gives you, it gives you the ability to manually set the aperture on your camera and the way to do that is by focusing your camera on the subject, press the shutter button half way down and your camera will give you a aperture setting and a shutter speed setting and to change the aperture setting in aperture priority mode what you need to do is hold down the shutter half way and then scroll to the right or to the left with the main control dial. By scrolling to the left I'm increasing the aperture. The maximum aperture that I have on this camera with a 35 millimeter lens is a 1.4 F stop. That's the widest or the most light I can let into the camera and at this setting the depth of field will be very, very small. I mean really razor thin millimeter. Somebody's the tip of somebody's nose at 1.4 F stop and you can see right now on my LCD screen that I will actually achieve a, I'm, I'm able to achieve a appropriate exposure because the shutter speed automatically compensates to only five hundred, one five hundredths of a second and that should give me the appropriate exposure. If I scroll the other direction to decrease the aperture it, it's kind of tricky because when you increase your aperture or when your decrease your aperture, making it a smaller hole, making less light come into the camera. The number that indicates that aperture actually increases so it's, they're a, they're kind of opposite. So I'm scrolling up here through larger numbers for aperture. I'm at 1.6, 1.8, and I can scroll all the way to 22 on this camera. That's the smallest aperture indicated by a 22 that I can achieve on this Canon lens. But you can see that once I've brought the camera down to a very small aperture the amount of time that the shutter needs to be open has increased quite a bit. All the way to 1/4 of a second which 1/4 of a second is actually going to be too long to hand hold the camera you're going to need a tripod to keep the camera steady. The a, probably the slowest shutter speed that you can use with a, with a hand held shot would be 1/60th of a second or 1/30th of a second if you're really, really steady with your hands. So yeah, once you set the aperture that your, that is desired, obviously at this one, this 22 aperture the, the aperture is very small creating a very wide depth of field which might be appropriate for landscapes or scenic shots. So I'm going to go ahead and leave my aperture there. Press the shutter half way down and go ahead and take the shot and that will give me a appropriate exposure. There was not any blinking on my shutter setting. So yeah check it out.
vanate
Feb 26, 2009
The depth of field will be narrow at 1.4, but will vary depending on your focal length.