July 2004

The megapixel race. Where did it start? Where will it end? The race is on In 1996, I bought my first digital camera, a Kodak DC40. At the time, it was one of the only consumer cameras available and at 768 x 504 resolution, it offered only a little more than one third of a megapixel. It didn't even offer a way to view your pictures on the camera, but it sure was cool. A year and a half later, I shelled out even more cash for one of the next generation: an Olympus D600L with a whopping megapixel of resolution. With that purchase, I became aware that the megapixel race had begun and that I'd be spending a lot of money on this new technology. The good, the bad, and the ugly A lot has happened since 1996. Manufacturers have added roughly a megapixel per year to keep us drooling and upgrading as the balance of power begins to show a strong shift from film to digital. As with many advances in technology, it is good to step back from time to time to take a look at where we've been and where we are going. How many megapixels do you really need? Is anything lost along the way or are the latest 8 MP cameras really 8 times better than the 1 MP versions from years ago? To answer these questions, we first need a little background. Since digital cameras became widely available in the late 1990's, the "consumer" camera, the small point-and-shoot style cameras marketed at the masses, have all had image sensors ranging in size from about 6 to 9 millimeters across, roughly 1/4 the size of a postage stamp. While the size of the sensor has not changed, manufacturers keep finding ways to cram more pixels into the same 1/4 postage stamp space. This may sound great at first, but as with most good things, there is a price to be paid, and that price is image noise (grain). An image sensor contains millions of photo sites, each of which is capable of collecting a charge as light hits the cell. Unfortunately, there is "overhead" involved since you must have some circuitry to store, amplify, and shift the charge over to digital data (the final image). As you decrease the ratio between the size of the light detecting part of the cell and the size or complexity of the electronics, noise increases. This noise can often be seen as grain in images and will look a bit like multi-colored "snow" from an old TV or even larger blotches of color depending on the filtering used. Megapixels, taming the herd An image sensor is a bit like a radio antenna. The bigger the sensor, the more light it can collect and therefore the less noise it will have. In contrast to consumer cameras, most digital SLR's have sensors 8 times larger (or more), allowing them to capture more accurate detail and also allowing them to operate effectively at higher speeds (ISO equivalents). Digital SLR's are also designed with much larger sensors in mind and they use larger, higher quality lenses so it is fair to say that the SLR camera in general is more "ready to accept" digital technology. On the other hand, consumer cameras can be more of a challenge when trying to increase resolution while holding the size of the sensor constant. Most consumer cameras were designed around the 6-9 millimeter sensor so increasing the size of the sensor is not cost effective because it will require that the camera bodies (and possibly the lenses) be redesigned. By increasing pixel count and keeping the sensor size constant, manufacturers can use last year's camera body, maybe add a feature or two, round off a few edges, change a few buttons, add a pin stripe, and sell the same thing they sold last year, but with more pixels. Most consumer cameras in the last few years have used what manufacturers like to call a "1/1.8 inch" sensor which amounts to a sensor about 7.2 x 5.3 millimeters. Obviously the advertised "1/1.8" nomenclature is no indication of the actual sensor size. The 1/1.8 architecture was generally used for consumer cameras in the 2-4 megapixel range. Once manufacturers hit 4 MP, noise was on the increase and compromises were being made. At 5 MP, some manufacturers began switching to what they call a "2/3 inch" sensor (8.8 x 6.6 millimeters), while the rest made the jump to the larger sensor when they went from the 5 to 8 MP mark. Looking at the sensor size alone, the increase may not look like a lot, but the slightly larger sensor amounts to a 1.5 times increase in overall size, giving manufacturers some breathing room to keep moving forward in the megapixel race and alleviating many complaints about noise. Putting it all into perspective So what does all this mean to people who are shopping for a digital camera? It simply means that you need to consider more than the pixel count when shopping for a camera that meets your needs. Don't buy into the "8 is better than 5" marketing strategy without considering other aspects of image quality: Your needs: What you need to do with the camera is usually more important than the latest jump in resolution. Do you need a point and shoot camera that is simple and will fit into your pocket? Do you need an SLR with manual controls? How much telephoto work do you plan to do and might you need interchangeable lenses? Does the camera offer features that you would find beneficial such as a direct print option or a camera dock to print quick shots on site? How fast is the camera from shot to shot? Most of these questions can be answered with a little reflection on your part and by reading through Steve's camera reviews. When you've narrowed the search to a few cameras that meet your needs, review some of Steve's samples at the end of the reviews from your various potential camera selections and compare similar shots to see which you like best. Print size: How big do you need to print? If you plan to print 4x6 or smaller prints most of the time with an occasional 8x10, your camera choices will be much broader because it doesn't take as much resolution to print small sizes. Many people argue that 300 DPI (dots per inch) are needed for true photo quality and you may have seen a reference to 300 DPI, but there really is no overall magic number. Prints will generally still look like photos and won't suffer from noticeable pixelization (jaggies) down to about 150 DPI if you print with high quality printing software. Below about 150 DPI, prints start to show jaggies (stair steps in diagonal lines that should be smooth) or they will start to lose some sharpness. Use the following as a rough guideline to how many megapixels you really need: For a 300 DPI print (super sharp photo intended for viewing up close) Print Size Resolution needed for 300 DPI print 4x6 about 2 MP 5x7 about 3 MP 8x10 about 6 MP 11x14 about 14 MP 13x20 about 23 MP For a 150 DPI print (photo quality when viewed at "arms length") Print Size Resolution needed for 150 DPI print 4x6 about 0.5 MP 5x7 about 1 MP 8x10 about 2 MP 11x14 about 3.4 MP 13x20 about 6 MP When using the tables above, note that it is important to realize that most larger prints are not scrutinized up close or with a magnifying glass and are meant to be viewed from a distance. You can often "get away with" much lower resolution when printing larger sizes simply because people will not usually notice that a 150 DPI print is slightly softer than a 300 DPI print unless they study it very closely. Also note that the idea that you can get away with resolutions as low as 150 DPI depends on the printing tool that you use and assumes that the tool (or you) upsample (interpolate) the print to avoid noticeable jaggies. Cropping: How often do you find the need to crop a section of the photo for printing? Does your technique or workflow often require that you crop the photo to get rid of unwanted portions of the image? If so, you need to take that into consideration when using the tables above since cropping an image reduces the resolution of the final print. Framing your photos better when you take the shot can reduce the resolution needed for the job because it means you won't have to waste pixels on things you don't need in the photo. Artifacts: What are you (or your intended "audience") sensitive to? Do you like super sharp photos? Do you notice noise (grain) in backgrounds like blue skies or shadows? Some of the latest 8 MP cameras have issues with chromatic aberrations (purple fringing around sharp edges or edges of high contrast). Do you notice this or see it as a problem when reviewing online samples? Does the camera render color that looks good to you? A lot of the buzz on the web regarding "my camera is better than yours" is subjective and the arguments for/against certain cameras will never be settled because different people look for different things in photos. Some focus on detail or resolution while others focus on accurate color, other artifacts in the images, and (lest we forget) some people actually focus on the photograph itself, the content, the framing, etc. User opinions: Be sure to check Steve's forums and other online resources to see what people are saying about certain cameras. You may look through samples and decide you like photos from a certain camera better than others only to find out later that you are not able to achieve the same quality as the reviewer who shot the samples. A quick check in a few forums might show a lot of complaints from people really having to "tweak" photos to get good (usually color) quality, so make sure that the quality you see is attainable with your experience and time. Photography: This probably shouldn't be the last topic because it is so important. The quality of your pictures ultimately depends on your ability as a photographer and your ability to utilize your tools. I've seen amazing photos from 1.5 to 2 MP cameras that beat photos from 6 MP cameras just because the photographer took the time to learn the tools of his/her trade (the camera itself and any after-the-fact editing tools) and was simply able to take good photos. Let us not forget that the "8 MP" logo on your camera can't make you a better photographer, nor can it make the camera any easier for you to use. Learning techniques and tools from listening to others can be the best way to improve your photographs. A lot of people spend a lot of money each year just to have the latest technology. That can be a disappointing and not very rewarding process if you are lured into thinking that a newer camera will make you take better photographs. The latest technology can help, but often it is more a question of whether you know how to use it and/or whether or not the camera suits your needs. — Mike Chaney Mike Chaney is president and chief software programmer for Digital Domain Inc and is the author of Qimage and Profile Prism software. He has a bachelor's degree in computer science from the University of Maryland, College Park. Mike worked for the federal government for 14 years as a senior software engineer, designing and deploying large scale workload tracking systems. He began developing digital imaging software in 1996 as a part time venture and due to the success of his software was able to resign from the government in 2001 to pursue his passion for digital photography and development of related software. Mike continues to develop and update his software and is also an active member of many online communities related to digital imaging. He enjoys helping others by discussing the latest topics, doing independent research, and sharing with others in order to take some of the "mystery" out of some difficult but key concepts in the field of digital photography.

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