You can also use a single point that exactly matches a small object you want to focus on, so there's no need to recompose after focusing.The individual AF point or points that you're using will normally illuminate in the viewfinder to give visual confirmation that it's locked on target, but this isn't always the case, as in the Pentax K-x.Some of the latest DSLRs, including the Canon EOS 600D, Nikon D5100 and Sony a390 feature articulating LCD screens.
DSLRs also often feature a high-sensitivity AF point at the centre, which focuses faster and can give greater accuracy when using a fast lens with a maximum aperture of f/2.8 or larger. 5: I've heard photographers talking about using a 'wide' aperture or a 'small' aperture, but what do they mean?
Those terms refer to the size of aperture being used.
This enables you to draw attention to key parts of the image, and conceal elements that might otherwise prove distracting.
Increasing the depth of field has the opposite effect, making more 'layers' in a scene appear sharp.
At any equivalent or effective focal length, larger sensors will give you a smaller depth of field - the depth of apparent sharpness in a picture.
As a result, the full-frame sensor size is ideal for portraiture, where you want to use a wide aperture to blur the background and make main subjects stand out (to learn more, see Full frame DSLR: do you really need one? The flip side is that APS-C cameras can be more useful than full-frame models when you want a large depth of field.
As well as affecting exposure, your choice of aperture also gives you control over the depth of field in an image, and this is one of the most potent weapons in the creative photographer's arsenal.
To learn more about how your aperture works, download our Free f-stop chart for understanding aperture, which is part of our ongoing photography cheat sheet series of infographics.
If you're shooting landscapes and want to keep the foreground as well as the horizon in focus, for instance, this can be difficult on a full-frame camera unless you use extremely small lens apertures, which can mean slow shutter speeds (click here for more quick, but great, landscape photography tips).