Shopping for a Digital Camera?
© 2002 by Stuart J. Whitmore
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation (FSF); with the Invariant Section being "Introduction", with no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is available on the FSF site.
This page is intended to give you an overview of some aspects you might want to consider when shopping for a digital camera. This was originally written by Stuart as a response to somebody asking him for a recommendation on a digital camera to purchase. He did not give a recommendation, since he was not current on what the market offered at the time, but chose to write this general guide instead.
Storage Medium and Image Transfer
This is something you will deal with constantly as you use the camera -- it must store the images and provide a mechanism to move them to the computer (or in some cases print them directly from the camera). It is very common to use a memory chip device for this, which will be called a variety of names. Other alternatives are direct writing to a CD or floppy disk -- so far I've only seen these alternatives in the Sony Mavica line. The storage medium in the camera will affect how you move the photos to your computer. Ideally the storage medium should be removable. Otherwise you can't use the camera when you're transferring images (it'll be wired to the computer), and you can't store more images than the camera can hold -- both of these limitations disappear when you have removable media. It would be OK if it was an option to wire the camera directly to unload the media (removable or otherwise), but ideally you should have an alternative device for unloading the images (which, for the Mavica writing to floppy or CD, just means a floppy disk drive or CD-ROM drive).
Images Per Unit of Media
Another aspect of the storage medium of use in any given camera is how many images it can store. The more it can store, the less often you will have to swap the storage media (or, for cameras without removable media, the less often you will need to move the images to the computer). Since the image size and compression (if any) will affect the number of images, it is more accurate to compare the actual size of the memory device (e.g., 1.4 megabytes (MB) for a floppy disk, a 5 MB flash card, etc.).
A key element of any camera is the quality of the images it creates. In a digital camera, one of the most important aspects of image quality is the resolution of the image. Literally, this means how many "dots" (picture elements, i.e., pixels) are used to build the image. All images are rectangular, and pixels are evenly distributed in a grid, so a 10x20 pixel image (smaller than a typical computer icon) contains 200 pixels. Digital cameras are listed according to their "megapixel" ratings; depending on who you talk to, one megapixel is either 1000 pixels or 1024 pixels. Marketers prefer the lower number!
Anyway, as with any dot-composed image, the more dots the better -- this is true for computer pixels just like it is for blobs from a paint brush or round pieces of paper. (Any image can be represented with one dot, but you won't understand what the image is!) If you want to view images on screen, common resolutions in digital cameras are oriented toward common screen resolutions on PCs -- e.g., 640x480, 1024x768, etc. Those are fine for on-screen viewing, but are insufficient for printed copies, especially for a print larger than a 5x7. Making a 8x10 from a 640x480 digital image will produce a terrible result because there's not enough image information to fill the space. (You also wouldn't want to make 8x10s from 110 film -- you need lots of image data to make a good enlargement, and 110 film has tiny negatives.)
Hardware vs Software Resolution
Digital cameras may promise a higher resolution (i.e., a larger pixel matrix) than their hardware can actually create. This is done by having the software "guess" what data should be used to fill in for the pixels not captured by the hardware. Generally speaking, you should only consider hardware resolution, which can be done by asking about the image capture component (typically a CCD, just like in a video camera).
Image Storage Format and Compression
In a nutshell, the camera should store images as JPEGs. You can read the rest of this paragraph to understand why, or you can skip ahead! For simplicity, you will want your camera to store its images in a common file format, so you don't have to convert images on a regular basis. A very typical format is JPEG. It's a good format for moving the image among a variety of computing platforms, and it can be readily sent via e-mail or posted on a Web page. If a camera stored its images in a proprietary format and required conversion to JPEG, the frequent image conversion would quickly prove annoying. Another facet of the file storage format is what kind of compression is used to make more images fit in a smaller storage area. JPEG uses "lossy" compression, meaning it throws away data (in an intelligent manner) to reduce file sizes. There are lossless compression formats, but I haven't seen any supported by digital cameras. There are uncompressed formats, but because of the cost of storage they also aren't generally supported by digital cameras. (Editing note on 8/20/2002: This is no longer true; with high-volume storage, uncompressed "RAW" images are supported in many modern cameras.)
Speed of Image Capture and Storage
This may be very difficult to compare, but the time that it takes the camera to store the image may have a significant impact on your enjoyment of the camera. One of my design complaints with my Mavica is the very slow speed of cycling through images, which hampers my ability to use it for things like company functions where photo opportunities don't wait for my camera.
Zoom (Digital Vs Optical)
Most digital cameras offer at least some zoom capability. 3x zoom is on the very low end, 10x is reasonable, and anything higher is icing on the cake. As with image resolution, the zoom can be either hardware (optical) or digital. With digital zooming, the software in the camera makes an intelligent guess at what data should fill in for the data that the hardware isn't capturing. Again, it's best to look at hardware (optical) zoom capabilities only. Digital zooming can become very grainy very quickly, especially without abundant light.
Roles (Tethered Stills, Untethered Stills, Tethered Video, Untethered Video)
Some cameras can be used to capture still images while connected to the computer, some can be used to capture stills while disconnected from the computer, some can be used to capture video while connected to the computer (e.g., for video conferencing), and some can be used to capture video while disconnected from the computer. Some offer multiple roles. If a mix of roles matters to you, keep it in mind; otherwise just look at the cameras for the particular role you have in mind. (This "shopping guide" is mostly oriented toward untethered stills.)
Full-Motion Video Capture
Some digital cameras offer the ability to capture full-motion video; for example, my Mavica can capture about 15 seconds of MPEG video at a resolution of 320x240. If this is something you might like to take advantage of, you should compare the resolutions, file sizes, and maximum recording time for a given resolution, and the file format (MPEG, QuickTime, etc.).
Sound Options (Input and Output)
I'm not sure about other digital camera lines, but my Mavica offers the ability to record sound (I think 5 seconds) with a still frame. In my opinion, this is poorly implemented and I never use it, but I suppose it might be useful in cases such as photographing evidence. "This is the right rear fender where the other car hit me..." Digital cameras can also make sounds, such as a "camera shutter" sound effect when taking a picture. It's very nice to be able to turn such noises off!
As is true with a film camera, you will want the controls to be easy to use. Part of a digital camera's controls may include settings for file resolutions, digital effects, etc. The usability of such features can be important since it is how you will interact with the camera. Comparison of this aspect is difficult via mail order or Web site listings, so you may want to visit a good camera store to get hands-on experience with the controls.
Depending on the hardware involved, the image capture in low light may be downright terrible. Flash support may not be very good, either. Consider the cases in which you might want to take photos in dim situations (indoor parties, outdoor night events, whatever), and consider how important this may be to you. If it's important, you can ask or look for details on low light performance.
At the low end, you'll have an on-camera flash only with no way to control it. More features would include being able to make the flash dimmer or brighter, being able to turn it off, being able to force it on, having it automatically turn itself on or off based on lighting conditions, and having support for a separate flash unit.
There are three basic viewfinder types, and some cameras will offer more than one. A basic one is essentially a hole through the camera that provides a hint of what your image frame will include, but it's not exact. This is the type of viewfinder on cheap 110 cameras, the Instamatic line, cheap 35mm point-and-shoots, etc. For an exact (or at least close to exact) view, there are LCD panels and conventional through-the-lens viewfinders like you'll find on good quality 35mm SLR cameras (either with direct optics or by using a miniature video display). The LCD panels can be useful, especially if they pivot and can be viewed from multiple angles; however, they also consume battery power. If you can find a combination of a pivoting LCD display that can be turned off to save battery life and a conventional through-the-lens viewfinder, that would allow a lot of flexibility.
Battery Charge Life
Changing batteries is like changing storage media -- you want to do it as rarely as possible. This may be difficult to compare between manufacturers, but within one manufacturer it might be possible to compare between models. The higher capacity the better, and, also like with the storage media, having a removable battery is much better than a battery that cannot be removed and requires the camera to be out of service for charging.
If it's of interest to you, you might compare what in-camera digital effects are available, and, if you get a camera with video capture, whether and which effects apply to the video. It is worth noting that most or all in-camera still image effects can also be done on the computer with software that is either supplied with the camera or readily accessible at no or low cost on the Internet.