Depth of field

The primary function of the aperture is to control the amount of light passing through the lens. The more light passes through the lens, the less time is required for the proper exposure. A faster exposure can freeze motion and alleviate camera motion, while a longer exposure can allow the subject to blur, conveying a sense of motion.

The aperture also affects the depth of field. A wider aperture narrows the depth of field, causing the foreground and background to blur, while a smaller aperture widens the depth of field, putting more of the scene into focus.

It's up to the photographer to decide which effects to show. Usually for a portrait you'd want the subject's face to be sharp and the background to be blurry. For a landscape, you'd generally want everything from the foreground to the background to be sharp.

What you want is a limited depth of field. There are three factors that control the depth of field: subject distance, lens focal length, and lens aperture. The greater the distance, the wider the DoF. The shorter the lens, the greater the DoF. The smaller the aperture, the greater the DoF.

One problem with compact cameras is that they have very small sensors. This means that they have short lenses. And short lenses mean they have wide depth of field. This is often an advantage, in that more of the scene is in focus. Unfortunately, this works against you when you don't want a wide DoF.

At the short end, the S2's lens focal length is 6mm. This will put just about everything in focus. Even at the other end, the focal length is 72mm. With a 35mm film camera, most portrait photographers use lenses at least 85mm in focal length in an attempt to minimize DoF to draw attention to the face and blur the background.

Unfortunately, the best you'll be able to do is to set the camera to the portrait mode, get as close to the subject as possible, and zoom in as much as possible. I realize the last two conflict with each other, you'll just have to find the proper balance for whatever you're photographing.

Get another camera :-(

You want to reduce the depth-of-field so that the subject is in focus while the foreground and background are out of focus and blurred. Depth of field (DoF) is dependent on three factors: distance, lens aperture, and lens focal length.

The farther the subject, the deeper the DoF. If you take a picture of a distant mountain peak, the mountain behind that and sunlit the clouds on the horizon will also be in focus. If you get close enough to a flower, you might get the front petals in focus while the petals in the back might blur.

The smaller the lens aperture, the deeper the DoF. Landscape mode, for example, will try to use a smaller aperture in order to get everything in focus while portrait mode will try to use a larger aperture in order to blur the background.

The shorter the lens focal length, the deeper the DoF. This is the killer. Due to the small size of the image sensor, the EX-Z750 has a very short lens: 7.9mm to 23.7mm. Even at the telephoto end of the range, 23.7mm would be considered very wide by film photograpers. A 24mm lens would give film photographers a sharp shot from foreground to horizon and, unfortunately, you're seeing that as well.

Note that the DoF is dependent on the actual focal length, not the 35mm equivalent you may have read about. This is a law of physics, not something that lens designers can easily alter.

Depth of field is one of the most useful creative controls on any camera.

It enables you to see how any given aperture setting will affect how much of your photographic scene will be in sharp focus. Aperture settings don't just affect how much light enters the lens, they determine how much of the scene in front of and behind the subject which you've focussed on will also be in focus. The distance between the nearest object in sharp focus and the most distant is called the depth of field.
Wide open apertures (i.e. lowest numbers) give you the shallowest depth of field and vice-versa.

Modern cameras always show the image in the viewfinder or LCD using the lens aperture wide open, regardless of what you've actually set: this allows maximum light into the lens to allow you to clearly see the scene and the lens only close down to the correct aperture at the moment that you press the shutter. The depth of field button (more correctly called the depth of field preview button) enables you to close down the aperture to what it's actually been set to so that you can see exactly what is in sharp focus; when you press it the scene will darken as there will be less light entering the camera, but if you look at a foreground or background subject which is out of focus before you press the button you'll notice that it becomes sharper when you activate the preview. The button will not have any effect at all if you have the lens set to it's maximum (lowest number) aperture, as the aperture that you're viewing the scene at is identical to the one you're taking the photo at.

Understanding depth of field and how you can manipulate it is vital to taking stunning photos:-

Say you want to take a photo of a bee on a flower: if you leave the camera set to auto, or select a medium to small aperture then the photo will show the bee, the flower, and everything in front and behind making a confusing and busy shot. If you select a wide open aperture then the bee will be in sharp focus (if you're really close, maybe only it's head), the flower, or parts of it will be in sharp focus, and the foreground and background will blur out making the bee and the flower the most important compositional elements in your shot.

Alternatively, you may be in a situation where you need to lift your camera quickly and take a shot without disturbing the subject. You don't know exactly how far away your subject will be, but you know it will be between, say, five feet and twenty feet. If you use your camera as normal, you'll see the shot, lift the camera to your eye, wait for focus (if using an autofocus camera, it might not even focus on what you intend). By the time the shutter has activated the moment has passed or the subject has seen or heard you and gone. Using depth of field you can manually prefocus to a point about a third of the way into your d.o.f. (in this case, ten feet) and select the correct aperture to give you a fifteen foot d.o.f. The setting varies with the lens, but you'll almost always get away with f8). When you see the right shot you just lift the camera and fire without worrying about focus and if you've done so correctly your subject will be sharply focussed. Of course, you could set the lens to minimum aperture, but this can result in the shutter speed being too low for the light conditions and causing unsharpness due to movement of the subject or your camera.

The technique is known as hyperfocal focussing and it explains why some lenses have various markings on them in various colours with aperture numbers next to them, they're a simple depth of field calculator for any given aperture setting. I'd provide a link but it's better if you search yourself as some sites go into what may be far too much detail about the subject.

Hope this has helped you, all that I ask in return is that you take a moment to rate my answer. If there's anything which you want me to clarify further then add a comment to my answer and I'll return as soon as I can to assist you some more.