Exploring the basics of a DSLR

- SLR, single-lens reflex, that's what these two cameras are right here. This is the camera design that people think of when they think of a serious, or a professional camera. And until a few years ago, this was the only viable option for a serious or professional photographer. Nowadays though, the camera landscape is a little more robust but there are many, many advantages to an SLR. The name, single-lens reflex actually explains the main advantage of this design so all we have to do is take apart that acronym to understand how this type of camera works. Single lens, sure enough, there's only one lens on this camera and you may think why in the world would it need more than one? But there have been many camera designs down through the years that have employed multiple lenses such as this twin-lens reflex. The lower lens here is used to expose the film while the upper lens is used as a viewfinder. This is kind of a brute force way to get around the problem of the film preventing us from being able to look through the main lens here. The problem with having a second lens for a viewfinder is that you don't see precisely the same composition as the lens that's exposing the film because the lenses are in slightly different locations. Also, you can't see the effects of any filters that you might have placed over your main lens which can make it difficult to properly set filters and to visualize their effects. With a single-lens reflex, I look through the same lens that exposes the sensor or film, sensor in this case. This is achievable through a combination of prisms and mirrors. Less expensive cameras might do it all with mirrors. If I take the lens off, you can see that here inside the camera there is a mirror so what's happening is light is coming through the lens, it's bouncing off of this mirror and going up. When it gets up into here, there's a prism or a series of members that bounces the light back through the viewfinder. So I am able to look through this viewfinder out the same lens that's exposing the sensor. However, it can't really expose the sensor right now because this mirror's in the way. So when I press the shutter button, the mirror pops up, the shutter opens and what you're seeing right there is actually the sensor. You can see it's got this kind of weird iridescent thing that it does. Then when the exposure is over, the shutter closes and the mirror comes back down. With the mirror up like that, my viewfinder is now blind. That's why when you take a picture with an SLR, the viewfinder blacks out for a moment because its light path out the lens is getting cut off. Most SLRs allow you to change the lens, and this is a wonderful feature. Interchangeable lenses give you a fantastic level of control over the quality, focal length, and lens characteristics of your camera. The downside to an SLR is that it's large. The camera body has to be big enough to hold this mirror as well as the prism or mirror arrangement that's up here and it has to have space for the optical viewfinder that's behind all of this. All of that takes space and those components contribute weight to the camera. Because of the mirror in front of the sensor, the lens has to be pretty far from the focal plane and that means that the lens itself needs to be bigger to project a large enough circle of light to cover that distance and completely cover the sensor. That adds more weight. Remember, the weight of a camera system includes all of the lenses that you carry with you also. So an SLR and a bag of lenses can quickly get heavy. SLRs fall into two major categories, full frame and crop sensor. The terms refer to the size of the image sensor in the camera and there are advantages and different disadvantages to different size sensors. With a bigger image sensor, the individual pixels on the sensor can be made larger. This camera has a larger sensor, and if I pop the lens up here you can see it as compared to, whoops, compared to this one. The larger sensor makes it possible to capture an image with very little noise. Noise is that speckled grainy stuff that sometimes appears in an image. You'll usually see less noise in a camera with a bigger image sensor. Depth of field is a term that we'll look at later, but it's basically how deep the focus goes in your image. Sometimes you'll want a very shallow depth of field to blur out the background and bring more focus to your subject. A larger sensor allows for much shallower depth of field than a smaller sensor. Smaller sensors, though, let you create smaller cameras and because they have inherently deeper depth of field they're great for situations where you want everything from near to far to be in focus, landscape photography, for example. Finally, cameras with smaller sensors are usually cheaper. Full frame means a camera with a sensor that's the same size as a piece of 35 millimeter film. Cropped sensor means a camera with a sensor that's smaller than a piece of 35 millimeter film. It's a crop of that larger size. SLRs currently come in a range of sizes and weights with a variety of interfaces and features. Their flexibility, performance, and image quality make them great options for any type of shooter.