Depth of Field (DOF for short), is usually associated with the aperture which is often used interchangeably with the word f-stop. The Aperture controls the amount of light that passes through the lens and onto the film; or in the digital world, onto the sensor inside the camera. This amount of light is determined by the size of the lens opening (the aperture) inside the lens. On the older traditional 35mm cameras, the settings on the outside of lens that controlled this function were called f-stops. That's why even though technically they are two different things; many writers use the words aperture and f-stop as if they were one and the same. It's like calling the door knob, a door. You do use one thing to affect the other, but they are NOT one and the same.
The greater amount of light the aperture allows in, the narrower the depth of field is, and visa versa; the less amount of light the aperture allows inside, the wider the depth of field is. Many beginning students get confused by this. Since the f-stop is what controls this light, the easiest way to remember it is:
Small number = small f-stop (f 1.8) = small amount of picture in focus.
Large number = large f-stop (f 32) = large amount of picture in focus.
The Shutter also affects this same light; where as the aperture controls "how much", the shutter controls "how long". If the shot is exposed for too long a time the photograph will appear washed out. If the shot is exposed for too short a time the photograph will appear too dark. This is commonly referred to as: over exposure and under exposure. The Shutter Speed (how long things are exposed); can be used to freeze things in midair (with a fast speed), or it can be used to intentionally blur something like water (with a slow speed).
As a general rule if you want to freeze something you want a shutter speed of 1/500th of a second 
or faster. As a general rule if you want to blur something (on purpose), you would use a slow shutter speed like 1/30th of a second or longer. Just remember, that generally you only want part of the picture as a blur so when you do use slower speeds, also use a tripod.
Wherever you focus your lens within a given image, there will be an area that is in focus and other areas that are out of focus. The area that is "in focus" is referred to as the "focal plane". The important thing to remember is that 1/3rd of this focal plane is in front of whatever you focused on, and 2/3rd's of the focal plane is behind whatever you focused on. By deliberately focusing 1/3rd of the way into your landscape shot and using a high number f-stop (like f-16 or f-22) you capture the greatest amount of the photograph in sharp focus.
Some people have the mistaken idea that if you just set your focus to infinity that it would do the same thing. The infinity setting that looks like an 8 turned on it's side, will give you an indication that says anything from 10 feet back will be in focus. So what happens if you want to include something that is less than 10 feet away? That's where the hyperfocal distance comes into play. When you use the hyperfocal distance you focus on something that is half of what the front infinity setting indicates, in this case that would be five feet. Since we know that 1/3rd of the area in front of your picture will be in focus, it gives the illusion that every part of your picture is in equal focus. Whether you use the 1/3rd in rule or set the hyperfocal distance, they both give you a greater sense of a large depth of field which is good for both landscapes and scenic shots.
If you always trust your camera meter and use what it tells you, you are using what we refer to as a standard exposure value. Exposure Values are those numbers that refer to the combinations of f-stops and shutter speeds that can give you an accurate exposure under a given light situation. Keep in mind, meters do not see in color, in order to make up for this it will average your scene, and give you a reading for 18% grey. All meters do this it's not their fault, that's how they were designed. But what happens if you actually want a white wedding dress to look white? Or what happens if you want that great black stallion to actually look black?
Just as many pictures look better after you take them into Photoshop and increase or decrease the brightness or contrast settings; many images actually look much better if they are exposed slightly more or less than what the meter suggests. This process of shooting above, directly at, and below what the meter indicates is referred to as bracketing. If you are in an especially difficult lighting situation or a location that is in and of itself very hard to get to . . . use bracketing. If your camera batteries are getting low, use bracketing. In short, if you have any doubts in your mind at all, use bracketing.
Most photo books strongly cover the subjects of f-stops and shutter speed. These are important, but there are other subjects, that many of them just skim over. Understanding the Focal Plane, Hyperfocal Distance, Exposure Values, and Bracketing will all greatly increase the tools you can use to make a better image.
This Article Written By: Tedric A. Garrison Cedar City, Utah
Tedric Garrison has done photography for over 30 years. In college; Tedric was an Art Major, and firmly believes that "Creativity can be taught." Today; as a writer and photographer he shares his wealth of knowledge with the world, at: http://www.betterphototips.com.
So, it's time for a digital camera huh? Well, buying one can be more than a little difficult. What types of features should you look for? Well, this guide will tell you that plus get you a little more familiar with what these cameras are capable of.MegapixelsWhen it comes to megapixels, the more the better. I recommend a minimum of 2, but 3 or 4 is great. We did a test to see if a camera with 2.3 megapixels (actually 1.92 - 1600 x 1200) could produce a good quality 8x10.Turns out it can, if you have the right paper and printer. We used HP Premium Plus photo paper with an HP 970 series printer and made a fantastic 8 x 10. Remember, I was a professional photographer before I got into computing, so I know a good print when I see it :-)The resolution at 8x10 (we had to crop in to make the picture proportional to 8x10) was only 150 DPI. Most printers would not make a real good 8x10 at that resolution, but this one did. So, if you want to be sure you can get good 8 x 10s, you may want to go with a 3 megapixel camera or better (that gives you around 200 DPI at 8x10 size, still not quite the optimum 300 DPI, but it looks good with the right printer).Optical vs Digital ZoomYou've probably noticed that most digital cameras have both a specification for digital and optical zoom. Pay the most attention to the optical zoom.The optical zoom magnifies (zooms in) using glass. The digital zoom basically crops out the edge of the picture to make the subject appear closer, causing you to lose resolution or to get an interpolated resolution (i.e. the camera adds pixels). Neither of which help image quality.Finally, make sure you get enough (optical) zoom. A 2x zoom isn't going to do much for you. A 3x is the average you'll find in most digital cameras will probably be good for most uses. More on lenses later.ConnectionHow does the camera connect to your computer? If you have a USB port in your computer, you'll want a camera that can connect via USB as opposed to a slow serial connection.On the other hand, if your computer doesn't have a USB port, is there a serial connector available for the camera you're looking at? If so, is it a special order and how long does it take to get it?StorageWhat does the camera use to store images with? If it uses a memory stick, make sure you consider buying additional sticks when you get your camera. A typical 8 meg memory stick that comes with a 2 megapixel camera only holds 5 or 6 images at the camera's best quality.Some cameras use a 3.5 inch disk for storage. Be careful of these!Although it may sound like a good idea, a 3 megapixel camera at high resolution produces a 1 meg file (compressed!). That's only 1 picture per disk.Here's a few more things to look out for when trying to make your digital camera purchase.Picture FormatsWhen you're trying to decide on which digital camera to get, check and see how many different picture formats it supports.You want something that can produce both uncompressed (usually TIFF) and compressed (usually JPEG) images. I personally use the high quality JPEG setting on my camera for most of my shooting. TIFFs are just too big and the difference in quality is not ascertainable by mere mortals.You also want to be able to shoot at a lower resolution than the camera's maximum. That way, If you're running short on memory, you can squeeze a few more shots on your memory stick.Auxiliary Lens / FlashThis was a biggie for me. While a 3x zoom may work for the "average" user, I needed something that allowed me to do some wide angle work as well as have a good telephoto lens.So, the camera I purchased a few months back was a Nikon Coolpix 990 (note that this isn't the only camera that can accept lenses). It has auxiliary lenses that screw into the filter ring on the front of the lens. I now have an ultra-wide fisheye lens plus a nice telephoto.In addition to lenses, I wanted a good flash. The flash that is built into most of these cameras gives you a top range of 15-20 feet - at best. I wanted a camera that could take a powerful auxiliary flash (again, the Nikon isn't the only camera that fits this requirement, but I liked it better than the rest). If you need more reach than the small built in flash can deliver, then make sure you can attach an external flash to any camera you consider.As an added bonus, if you get a camera that can take an external flash, you can place that flash on a bracket and eliminate red-eye.Flash DistanceSpeaking of flashes, make sure you check the distance the built in flash is good for. You don't want a camera with a wimpy flash that only travels a few feet (well, unless you can get an external flash for it as described above).Battery TypeThis may not sound important, but it is. Anyone who owns a digital camera can tell you they eat batteries the way a sumo wrestler eats at a buffet.Make sure the camera can run on regular (or rechargeable) "AA" type batteries. You don't want a camera that eats through expensive lithium batteries every 10 shots or so.One thing to remember about digital cameras, they do eat through batteries. I recommend getting some Nickel Metal Hydride rechargeable for it. I have some for mine and they have saved me a fortune.Final NotesChoosing a digital camera isn't easy. There's a huge selection out there and only you can determine which features you need.For instance, if you shoot wildlife photos, a small 3x zoom probably isn't going to cut it (unless you can attach auxiliary lenses to it). If you shoot lots of close-ups, make sure the camera has some sort of macro capability. If you shoot big group photos indoors, an external flash may be necessary.My advice is to make a list of things you want to be able to do with the camera then go to somewhere that can help you make a good purchase decision.Finally, buy the BEST camera you can possibly afford. Or wait until the price drops on one with the type of features you want.Buying Guide: Digital Cameras Side-by-SideTry this: Digital Photography Review - Here you will find all the latest digital photography and imaging news, reviews of the latest digital cameras and accessories, the most active discussion forums, a large selection of sample galleries, a digital camera database and buyers guide and the most comprehensive database of digital camera features and specifications.
Depth of Field (DOF for short), is usually associated with the aperture which is often used interchangeably with the word f-stop. The Aperture controls the amount of light that passes through the lens and onto the film; or in the digital world, onto the sensor inside the camera. This amount of light is determined by the size of the lens opening (the aperture) inside the lens. On the older traditional 35mm cameras, the settings on the outside of lens that controlled this function were called f-stops. That's why even though technically they are two different things; many writers use the words aperture and f-stop as if they were one and the same. It's like calling the door knob, a door. You do use one thing to affect the other, but they are NOT one and the same.
or faster. As a general rule if you want to blur something (on purpose), you would use a slow shutter speed like 1/30th of a second or longer. Just remember, that generally you only want part of the picture as a blur so when you do use slower speeds, also use a tripod.
Just as many pictures look better after you take them into Photoshop and increase or decrease the brightness or contrast settings; many images actually look much better if they are exposed slightly more or less than what the meter suggests. This process of shooting above, directly at, and below what the meter indicates is referred to as bracketing. If you are in an especially difficult lighting situation or a location that is in and of itself very hard to get to . . . use bracketing. If your camera batteries are getting low, use bracketing. In short, if you have any doubts in your mind at all, use bracketing.