There's really only one critical difference between a digital camera and a film camera, and that's the fact that a digital camera has a silicon image sensor sitting on its focal plane instead of a piece of film. Sure, digital cameras can also be really weird shapes, and they have LCD screens and so on and so forth, but it's that image sensor that makes digital a dramatically different technology than analog photography. Becuase the physics of light stay the same whether you're shooting digital or film (thank god), the science of digital photography is mostly identical to the science of analog photography.
When you buy a film camera, you don't have to worry about the quality of the images it will produce because you'll select your imaging technology later when you select a film. So, when you buy a film camera you spend your time looking for features, feel, and lens availability, and only later worry about the imaging properties of a particular film. With digital, you've got to consider all of these at the same time.
In this column, we're going to begin a very detailed discussion of all of the issues and considerations you need to make when hunting for a digital camera. The good news is that nowadays, digital camera shopping is not as complicated as it used to be simply because the technology has matured to the point where there are lots of really good cameras out there. With just a little diligence, you should have no trouble finding a camera that yields very good images, delivers the features you want, and is reasonably affordable.
Before you begin shopping, though, there's one important fact that you simply have to accept: The camera you buy will be replaced by an "improved" model within a year. Of course, this is true with most things digital, and it can cause a lot of people to feel that they should wait because something better is going to come along. Years ago, when the next generation meant a step up from 1 megapixel to 2 megapixels, then next-generation envy was a reasonable concern. But these days, the next generation is not necessarily going to be dramatically improved. For the most part, new models pack changes in feature sets and body designs, and occasionally improvements in image quality. However, in something of a positive sign about the state of digital camera technology, it's important to recognize that new models sometimes yield inferior results to their predecessors.
Because of the general high quality of the current technology, it's now possible to hedge your bets against obsolescence by picking a camera that has the features you need for the type of shooting and output that you require. That way, although spiffy new features may be a nice tease, they won't necessarily be a requirement.
How Much Can You Pay?
Obviously, as with making any kind of choice, choosing a camera is a process of winnowing down the available models until you arrive at a -- hopefully -- obvious conclusion. The digital camera market is huge, with new models arriving all the time, so any step you can take to eliminate candidate cameras is a step in the right direction.
Whether you're looking for a cheapo point-and-shoot or a pro-level SLR, the first step to take, then is to come up with some idea of what you're willing to pay. Once you've come up with an amount of money that you're comfortable with, your goal is to find the best camera that you can for that price.
"Best," of course, should be defined by the particular needs of the type of shooting you do. Obviously, if you need the ability to output large, high-resolution prints then you're going to want a high-resolution camera. If you want maximum image quality and flexibility, then you're going to want a digital SLR. If maximum portability is the most important concern, then obviously a small point-and-shoot is going to be the best solution.
Delineating some broad camera parameters -- SLR, small size, high resolution, etc. -- will further slash the field of contenders.
Taking this first step not only pares down the field of cameras, it also possibly shields you from the concern about whether or not you've bought the right camera. Once you realize that "best" is not an absolute term, then you'll be less concerned about where you stand when a new camera comes out with super-resolution, or extra-tiny size. Your concern is to get the camera that will afford the type of shooting you need to do.
What Resolution Do You Need?
After zeroing in on a price range and overall idea about what type of camera you need, you've probably already eliminated a good number of candidates. The next big cut is going to be to make a resolution choice.
Digital camera vendors will try to sell you on a very simple resolution guideline: More is better. Fortunately, for reasons discussed in the last column, this isn't entirely true. Higher resolution does not necessarily yield better images, and paying for pixels you don't need is a waste of money.
Obviously, more pixels means more resolution, which should mean more detail, which should yield a better picture, but this isn't always the case because the quality of the pixels is often as important as the number of pixels. A high-resolution camera with a lousy lens is going to yield a whole bunch of really bad pixels. Consequently, it's important not to get caught up in the resolution wars that many vendors choose to fight.
Instead of simply deciding to buy the most pixels you can afford, it's much better to consider how you might be outputting your images, and select a resolution that supports that type of output. If you need to create 13-x-19-inch prints, then you'll want a high-resolution camera. But if the bulk of your work is smaller prints, or Web output, then you probably don't need to pay for extra pixels. The fact is, there's a lot you can do with just 3 or 4 megapixels.
Because larger prints are viewed from greater distances, resolution (measured in pixels per inch) goes down as you increase print size. In other words, for a 13-x-19-inch print, you can easily get away with 200 pixels per inch, because people will be viewing it from farther away than they will a 5-x-7-inch print, which will need around 300 pixels per inch.
Figure 1 shows relative print sizes, along with the camera and print resolutions that you'll need to achieve good prints at each size.
Figure 1: You can select a resolution class by trying to determine what size prints you'll most likely be making.
Higher resolutions buy you more than just bigger prints, of course. With more pixels at your disposal, you can enlarge parts of your image, and crop to create a full-size print of a smaller portion of your image. However, if your workflow is more snapshot-oriented -- take the picture and get it into production as quickly as possible -- then resizing and cropping may not be anything you'll ever do.
Of course, just because you choose a particular resolution doesn't mean you're stuck with a particular print size. With a capable image editor, you can up-sample your images a fair amount before the image visibly degrades. So you may be able to coax a larger print out of your chosen camera.
Be aware also that a difference of a single megapixel does not necessarily translate into much greater area. A 50-percent increase in the number of pixels in a camera adds only 22.5 percent more print area. That's the difference between an 8x-10-inch print and a 10-x-12-inch print -- not a tremendous increase in size. Of course, the higher resolution camera might give you better detail at the same size than the lower-resolution camera.
Perhaps the best way to decide is to figure out what print size you'll most often be outputting, and then go up one resolution class. This will give you good results at your most-used print size, with an option to print a little larger, and extra pixels for times when you want to crop and re-size.
What's next?
Making price and resolution decisions will do more to narrow the field of possible candidates than any other choice you'll make. From here, you're ready to start looking at some particular cameras and comparing their features and abilities, topics we'll be looking at in the next installment of "Framed and Exposed."
