Hello,
I'm deeply interested in learning photography, which is why I decided to join this forum. While I've taken many pictures, I have a lot to learn and there is still plenty that I don't understand. I've procured some books to broaden my understanding, but I'm finding the learning curve to be somewhat steep. Concepts like exposure and a camera's many components continue to puzzle me, but I'm hoping that by becoming a member of this forum, I will be rewarded with a heightened knowledge of the ins and the outs of photography.
I am currently using a Canon Rebel T3I.
- Walrus
Ok, well exposure isn't really bad once you get the hang of it. Exposure is all about light. You want to let enough light in so that the sensor can create a proper image. The three components of exposure are Aperture, Shutter Speed and ISO.
So we'll start with Aperture. This is a measure of how wide an your lens can open. The wider the lens opens, the more light it lets in. The lower the F number, the wider the lens will open. I know that seems backwards at first, but F numbers are actually fractions, so the lower the number, the wider the lens will open to let in more light. The upside to a wide aperture is it lets in more light, which allows you to reduce ISO or increase shutter speed using the same available light as a more narrow aperture would allow you to use. The downside is that when you increase the aperture (lower the F number) you get a narrower depth of field and it's something you need to be aware of when increasing the aperture. There are times when a narrower DOF can come in handy, I'll cover that a bit later.
The second component to exposure is shutter speed. The slower your shutter speed the longer the shutter stays open, so the more light that reaches the sensor. So by using lower shutter speeds you can take pictures with less light than what a higher shutter speed can capture and still get a proper exposure. The downside to slower shutter speeds is blur - both motion blur and camera shake. If your subject is moving and the shutter speed isn't high enough the end result will be motion blur. Also when you hand hold a camera your not a stable platform. If the shutter speed is low enough this movement of the camera as you hold it can result in "camera shake" which will also give you blur. You can compensate for camera shake using a tripod or monopod, and a lot of newer cameras have some form of image stabilization available, some are built into the camera body and some are built into the lens, but both attempt to do the same thing and that is compensate for camera shake.
The last component of exposure is ISO - the higher you set the ISO the more senstive the cameras sensor becomes to the incoming light. This allows you to shoot with narrower apertures or faster shutter speeds when the lighting isn't that great. The downside is when you increase your ISO you also start introducing noise into the image, and the dynamic range starts to be affected so the colors don't "pop" quite as much.
So the trick is to balance these three in such a way that you get the best results for the kind of image you want. Increase the aperture and you can decrease the ISO or increase the shutter speed or maybe a little of both. Decrease the aperture and you might need to decrease your shutter speed or increase your ISO to compensate.
If your shooting a cityscape at night for example, your target isn't really moving so you don't need to worry about motion blur. So you mount your camera on a tripod and use a very long shutter speed so you can keep your aperture low and your ISO low and get the best shot.
If your shooting sports or a moving target like wildlife you want to keep your shutter speed high to avoid motion blur, so as a result you'll need a wider aperture or a higher ISO or a combination of both to keep your shutter speed high.
That's pretty much the very basics of exposure, I'm sure others can add a lot more detail but I think that pretty much covers the basic concept at least. If you want my recommendation, try shooting in Aperture Priority mode (AV on your dial). Experiment by adjusting your aperture and see how the camera starts changing the ISO and shutter speed to compensate.
Ok, now real quick on depth of field. When your camera focuses on the target whether your letting the camera choose a point to focus on or your choosing it yourself that becomes your point of focus. Everything on the same horizontal plane of that point will be in focus. As you start moving away from that horizontal plane, things will start to become more and more out of focus.
Aperture affects this depth of field. The wider your aperture the faster objects not on the same horizontal plane will become out of focus. As you increase the F number you increase the distance an object can be from that focus point and still be in sharp focus. There are other factors that affect this depth of field, such as your distance from the focal point, the focal length of the lens, and of course the aperture it's set too. There are a lot of depth of field calculators out there you can use to get a good grasp on how these things affect your depth of field, and of course this is something else I recommend you practice for yourself so you can see the real world results of how these things all fit together.
Ok, that's the quick and dirty version at any rate, hopefully that helps.
