A few years ago, all digital cameras were "point and shoot" and they were very expensive compared to film cameras. Digital prices dropped rather quickly as digital sensor resolution continued to increase. Soon enough digital "point-and-shoot" cameras were available at every price point from a basic snapshot to the more serious models geared at the prosumer market.

At the dawn of the consumer digital SLR in 1999, a 2.7MP (megapixel) DSLR with an APS C sensor was considered an incredible buy at $5000. Tremendous growth in market share and the falling prices of DSLR cameras in the years since have created new buying options for those shopping for an upgrade to an existing camera or even a first camera. This has been particularly true in the last couple of years. All of the old reasons to own a point and shoot instead - with lower cost leading the way - have fallen by the wayside as the DSLR has continued to evolve and become both very price competitive with P&S and much easier to use.

However, many new DSLR buyers are walking into a brave new world with blinders on. The first question everyone should ask is why should you buy a DSLR instead of a point and shoot?  Are there real technical advantages to DSLRs?  After all the ads for point-and-shoots are hyping the same range of sensor resolutions that you will find in digital SLR cameras, so why buy a DSLR? The answer to that question is what really prompted this article.

Yes, you can buy 10MP and 12MP point-and-shoot cameras - the same megapixel range as current mainstream DLSR cameras - but they cannot possibly produce the same image quality over the same wide range of shooting conditions as a digital SLR. The reason why is simple physics, as the point-and-shoot sensors are much smaller than sensors in a DSLR. In fact, that is also the very reason why point-and-shoot digital cameras were the only choices in the market for a few years.

The early sensors were much lower megapixel resolutions, far too low to begin to compete with film photography. Photo hobbyists saw few advantages in moving to a low resolution system since the reason they used an SLR was high image quality. It wasn't until resolutions reached the 2-4MP range that there was any interest in a digital SLR.

The early sensors were also very small, developed primarily for video usage. The 1/2.7" compact sensor is 5.3x4.0mm and the larger 1/1.8" is 7.2x5.3mm - compared to 35mm at 24x36mm. These typical compact sensors are just a tiny fraction the size of 35mm sensors, and these sensors were among the largest available in P&S digital cameras. Some tried to develop proprietary systems based on a smaller sensor size with more compact lenses, but nothing caught on in the industry. The cost of early sensors was also astronomical, making the early digital SLR cameras only useful for production, high volume photography where the cost could be justified.

Finally, early digital development saw sensor resolution and size in constant evolution. With sensor size changing with each new generation, it was much easier to design a point-and-shoot camera around each new sensor generation using a dedicated and non-interchangeable lens. Until sensor size stabilized, a digital SLR that used either existing 35mm lens systems or a new "standard size" was not practical.

Sensors Today

In the above chart, the sensor sizes for today's DSLR cameras are in the range of 4/3" and APS C. A few top pro cameras now sport 35mm-size sensors and are referred to as full frame. Comparing this to Compact or Point and Shoot cameras today we generally find a 1/2.3" to 1/2.5" sensor. A few top-of-the-line compact cameras, like the Canon G9, feature a 1/1.8" to 1/1.7" sensor. To see the difference in the relative size of P&S sensors and DSLR sensors, look at the graphic below.

The very best compact cameras have sensors around the 1/3" to 1/2" range. The APS C to 4/3 sensors of the bulk of today's digital SLR cameras are huge by comparison. The developing push for full-frame at the top of the current DSLR market is a move to a sensor that is a bit more than double the size of today's APS C sensors. The approximate 24mm by 16mm APS C is the same size as the 1/2 frame 35mm championed by Olympus in the film era.

This size actually harkens back to 35mm motion picture film that became the standard on which most of the SLR lens systems are based. 35mm motion picture film contained images of around 24x16mm, and 35mm still film just turned the spool direction and used double the frame size. In fact, some early 35mm still cameras were referred to as "double-frame" cameras.

Why Does Sensor Size Matter?

In some of life's arenas bigger is better, but in computers and electronics we almost always see a trend toward smaller and smaller traces producing chips with higher and higher densities. So the question becomes why is a 10MP DSLR sensor any better than a 10MP Compact or Point and Shoot sensor?

The simple answer is that computer chips are digital devices, made up of transistors that register on and off (1 and 0) states, which are then combined to create the information we crunch in a computer. Digital sensors, on the other hand, are analog devices used to gather light and color information. Every digital camera then has some means to convert this analog sensor data to digital information in its processing path. Devices that communicate on and off do not require the sensitivity of devices that gather and convey more complex data like a digital sensor pixel.

Unlike digital data, all pixels are not created equal. Larger sensors, such as those used in digital SLR cameras, have larger pixels. All things being equal the larger pixels have more light-gathering ability over a given unit of time. This translates into two very important considerations for photography.

First, larger pixels exhibit lower noise than smaller pixels under the same conditions. This improved signal-to-noise ratio means that your 10MP DSLR image will likely produce better, sharper, clearer prints than the smaller 10MP compact (point and shoot) cameras. This improved SNR also means larger sensors produce a wider dynamic range (a greater range between the lightest and darkest elements of the photo).

The second aspect also relates to light gathering ability. Large DSLR sensors have more ability to gather light, which means they generally are more effective over a much wider range of lighting conditions than a compact camera. Many compact cameras are perfectly acceptable at ISO 100 but are very noisy by ISO 400. Most DSLR cameras with their larger sensors produce very acceptable results to ISO 800 or 1600 - ISO options not even available on most compact cameras. Some newer DSLR cameras even offer options of ISO 3200, ISO 6400, or even higher.

Why All these Different Sensor Sizes?

35mm first appeared on the scene in the 1930s and the film format simply took 35mm motion picture film and spooled it into a light-tight canister. By the 1960s, with point-and-shoot and developments in SLR technology, 35mm had become king of the film formats. Even as film manufacturers tried to introduce other film formats, 35mm continued to grow and prosper.

The SLR evolved in 35mm space and the world appeared orderly on the surface, but the only real constant was the size of the film. It was 35mm, but SLR manufacturers each championed their own lens mount and their exclusive lens line for their SLR film cameras. The primary advantage of the SLR was the ability to look through a wide variety of interchangeable lenses, and to accurately focus, meter, and later auto-focus through the viewing lens. As in today's digital SLR market, each manufacturer had their own lens mount, and lenses developed for one mount would not fit and work on others, i.e. a Nikon lens would not fit or work on a Canon camera.

APS (Advanced Photo System)

With the very early developments in digital photography, Kodak, Fuji, and others saw the handwriting on the wall for film photography. One of the ongoing complaints about 35mm film, however, has been that the 2:3 image format required image loss in almost every standard print size. Neither 8x10 nor 5x7 is a 2:3 ratio and both required cropping of the 35mm negative.

In 1996 a new APS (Advanced Photo System) initiative by Kodak, Fujifilm, Minolta, Nikon, Canon, and others was introduced to save film by standardizing on new ratios and adding new "computer-like" data storage capabilities in the taking and processing of film images. APS included a new film size - 30.2mm x 16.7mm - that could be printed full-frame (H or HDTV format), or use standard crops of 25.1mm x 16.7mm (C or Classic 2:3 format) or 9.5mm x 30.2mm (P or Panorama). Actually, the image size that was always shot was the 30.2mm x 16.7mm, and the other sizes were just standard crops.

The industry was confident they could sell APS, which in the most common C view was only about 55% of the already small 35mm size. Some manufacturers like Minolta developed new APS lens lines with smaller cameras and lenses, and Canon and Nikon developed APS camera bodies that could mount their regular lenses - and a few custom APS lenses.

In the end, APS failed in the film market. Industry pundits generally say APS failed because the negative was just too small, but it is more likely that it failed because it was just too late. Digital was on the near horizon, and many photographers did embrace smaller digital sensors while they rejected the smaller APS film format.

APS film is not that important in our discussion of digital photography, but the APS standard is important because it was also a standard for digital development. At the time of the APS initiatives, it seemed reasonable to aim for development of digital sensors for that same APS format, so lenses for both systems were interchangeable.

Most in the industry aimed for the APS C size sensor, which would be about 16.7mm x 25.1mm - the same ratio (2:3) as the classic 35mm format. Most manufacturers, burned by bad decisions in the APS film debacle, decided to keep their existing 35mm mounts, so their existing 35mm lenses could be used. They hedged their bets. This pleased current 35mm system owners, and camera makers could see if the new digital SLRs took hold. Once they were satisfied there was a market for digital SLR cameras, they could develop new lenses with a smaller image circle.

Canon and Nikon worked with Kodak in the early digital years to use their best film bodies with the current state-of-the-art Kodak sensors. These early DSLR cameras were incredibly expensive with massive power requirements and pro only. This development line culminated in the full-frame Kodak DCS Pro SLR/n and SLR/c. Those two cameras were the end of Kodak digital SLR cameras, although the company is still very active in the development and manufacture of digital imaging sensors and compact digital cameras.

Camera manufacturers introduced digital SLR products that revolved around the strength of their SLR business, the sensor capabilities they brought to manufacturing, and the relationships they had with other sensor manufacturers. Most of today's consumer DSLR cameras are based on sensors approximately APS C size, but they vary from the Olympus 4/3 sensor at 225mm² to the full-frame 35mm size with an area of 864mm².

Discussion of sensor size always tends to generate passionate discussion of the advantages of one manufacturer's sensor format over others, but please keep sensor sizes in perspective. The smallest 4/3 sensor still has 5.2x greater sensor area than the 43mm² sensor used in the 12MP Canon G9. The 4/3 sensor is 9x greater area than the common 1/2.5" compact sensor with an area of 25mm². Differences in digital SLR sensor size do matter, but they are very small compared to the difference in area between compact point and shoot digital sensors and today's digital SLR camera sensors.

Sensor Size and Multipliers

Canon had become a dominant player in the SLR market after their successful launch of the EOS all-electronic mount for AF. Canon was also large enough with enough resources to develop and manufacture their own sensors. Canon launched a professional standard APS-H camera, with a 1.3X lens multiplier that used existing Canon 35mm lenses. Later, when Canon was ready to create a consumer digital SLR market they used a smaller 22.2x14.8mm sensor with an area of 328mm² and a lens multiplier of 1.6X. This is 38% the area of a full-frame sensor.

More recently, Canon has championed the full-frame sensor in their pro cameras and in their pro/amateur 5D model. Larger sensor manufacturing cost has dropped as digital sensors have evolved and it now appears likely the APS-H (1.3X lens multiplier) will eventually drop form the Canon line. Since no lenses depend on that image circle all current Canon full-frame lenses, such as those used with the APS-H cameras, will remain usable on the full-frame sensor pro models that will replace them.

Nikon, Pentax, and Minolta all had significant success in the 35mm film market, so all three had a vested interest in preserving their 35mm lens mount and keeping their current 35mm system users happy. However, none of these three had the resources to develop and manufacture their own sensors, so they partnered with sensor manufacturers to produce digital SLR cameras. In recent years that partner has been Sony, so all three manufacturers have basically adopted a larger 23.6x15.7mm sensor with a 1.5X lens multiplier.

Sony purchased the Photo Imaging division of Konica Minolta in 2006 and carried on the Minolta lens mount under the Sony brand. Today Sony both manufactures their own Sony brand cameras with Sony sensors and they continue to sell sensors to Nikon, Pentax, and Samsung.

Olympus was a huge player in the digital compact market as the market began its slow move to the digital SLR. While Olympus had been a very successful player in the film SLR market, they lost market in the SLR Auto-Focus wars kicked off by the success of the Minolta 7000. Olympus AF cameras remained a fringe product and Olympus eventually exited the market to concentrate on their compact digital offerings.

Olympus had a stake in the compact market remaining dominant and they had little legacy 35mm business to protect. Both developments made them late to the digital SLR market, but they made the best of it with a different approach than the other DSLR players. Olympus developed a new all-electronic DSLR lens mount and camera system based around a Kodak sensor with a 4:3 ratio instead of the 3:2 common in 35mm. With no legacy lenses to protect, the concept of lens multiplier is basically meaningless when talking about the Olympus DSLR system, but the diagonal is 1/2 the 35mm full-frame so lenses are equivalent to a 35mm lens at twice the focal length.

Olympus and its partners also made the 4/3 standard open - that is, it's available to any manufacturer. Currently Olympus, Panasonic, and Leica are producing 4/3 cameras and lenses but other manufacturers may join them in the future. Olympus is also now using sensors manufactured by Panasonic, a development partner, in their 4/3 cameras.

Sigma is best known as an independent lens manufacturer, but they have been producing SLR camera bodies for almost 30 years. Sigma introduced their first digital SLR with the SD9 in 2002. Sigma is the only DSLR manufacturer to use the unique Foveon sensor, which captures all three colors in a digital image in three layers - red, blue green - on a sensor. All other current digital sensors are based on Bayer sensors, which capture all three colors in mosaic patterns on a single sensor layer. Colors are then restored by an interpolation process called demosaicing, which theoretically converts the three color mosaics into smooth full-color images.

For this discussion, the current Sigma SD14 should be considered a niche DSLR player with very small market share. The Foveon sensor falls between 4/3 and the Canon 1.6 in size and has a 1.7X lens multiplier. Sigma is the only third party lens maker to produce lenses for all the camera systems discussed here. Some are full-frame designs with digital coatings to mount on full-frame or smaller digital sensor SLRs. Other designs are based on the largest 1.5X APS C image circle and are designed to work with smaller DSLR sensors ranging from 1.5X to 2X lens multiplier.

CCD and CMOS

At the dawn of the digital SLR era, almost every sensor was a CCD (Charge Coupled Device). CCDs were relatively easy to make, but they were and remain basically a single function sensor. CCD sensors create very high image quality and low noise, but they require support circuitry for almost every function provided by the CCD. The CMOS (Complementary Metal Oxide Semiconductor) sensor was always a possible alternative in sensor design, but manufacturing CMOS sensors was very difficult with the technology available at that time. CMOS sensors are inherently lower image quality and higher noise than CCD, which led some experts to predict that a production CMOS sensor for DSLR imaging would never be made.

There are many reasons manufacturers would have preferred the alternative of the CMOS sensor. While difficult to manufacture they are much cheaper to make in volume than CCD sensors. Power consumption for CMOS is inherently lower than the CCD sensor. In addition, the CMOS sensor lends itself to integrating other electronics, such as the analog to digital conversion and noise reduction electronics into the sensor itself - something not really possible with the CCD design.

Those who did not think a commercial CMOS sensor was possible were silenced with the introduction of the $3000 Canon D30 in the fall of 2000. Canon has championed the CMOS sensor, almost exclusively, since that time. However, in the past year other sensor manufacturers have been able to produce their own CMOS sensors. As a result, almost every new sensor introduction in recent months has been CMOS.

In fact, Sony was the first to market with a 12MP+ APS C size CMOS sensor, used in the Nikon D300 and Sony A700. This was followed in about 6 months by the introduction of the Samsung 14.6MP APS-C CMOS sensor in the Pentax K20D. It appears other sensor makers who previously trailed Canon in CMOS development are now the ones pushing the envelope in CMOS sensor development. Sony has also announced a 24.81 effective megapixel CMOS sensor that will be used in a full-frame Sony later this year that will likely be called the A900. The Sony and Samsung thrust into CMOS sensors makes more sense when you realize that Sony and Samsung jointly own several recent patents in CMOS technology. Panasonic is also producing CMOS sensors as seen in their LiveMOS sensors used in the Olympus E-3 and E-501/410/420.

LEFT: Conventional Image CMOS Image Sensor Circuit Structure
RIGHT: Column-Parallel A/D Converter CMOS Image Sensor Circuit Structure

Sony has also taken advantage of another CMOS capability by combining analog to digital conversion and image noise reduction on the CMOS sensor itself in the 12.2MP A700. Some photo review sites had apoplectic fits when they realized Sony was doing noise reduction on the A700 chip, but this is an inevitable development. This move to larger integration of electronics into the CMOS sensor module is just starting, and it could eventually lead to a much larger scale integration of digital image processing functions into the sensor chip - or even a camera on a chip.

Bayer vs. Foveon

This title is something of a misstatement, as it would more accurately be Foveon/Sigma versus everyone else in the world. All DSLR imaging sensors except the Foveon use Bayer technology. Digital color images are created by capturing red, blue, and green pixels and then combining them to create a full color image.

All current sensors except one use Bayer technology.  The sensor consists of X megapixels, or light gathering cavities. The sensor is covered with a Bayer array, which is a series of microlenses that allow only certain colors to fall in certain cavities (or pixels). The microlenses are arranged in a defined grid that consists of alternating red-green and green-blue filters.

If you noticed there are twice as many green as red or blue areas in the above image, that is by design in the Bayer array. The human eye is more sensitive to green light than red or blue and the Bayer array uses this fact to produce images that appear to have finer detail and less noise. The doubling of the green receptors is corrected in the image processing.

There is no demosaicing or interpolation step with the Foveon sensor. Where before there was one pixel of color information, the Foveon is now capturing red, green, and blue data pixels in the same pixel location. On the surface, this certainly appears a superior way of capturing color images, but things are not always as they appear. It is fair to ask: if this approach is so good then why is Sigma, a minor player in the digital camera market, the only company to embrace the Foveon sensor? A closer look at Foveon specs helps to understand some of the issues.

The top current Foveon sensor is the 14.1MP Foveon used in the Sigma SD14 digital camera. Foveon gets to the 14.1MP total by counting all pixels used to create the finished image, which is 2688x1768 pixels or 4.7MP. Many would argue this is fair since each pixel in a competing 14.1MP is only collecting one piece of color information. However, the practical reality is that a 14.1MP Foveon is reported to be about equivalent to an 8MP Bayer DSLR when shooting JPEGs and about as good a 10MP camera when shooting in the preferred and native RAW mode. The apparent resolution then is somewhere between the 4.7MP image size and the 14.1MP that are used to create that image.

Several other issues have also held back Foveon. Where the best Bayer cameras can now capture useful images at ISO 1600, 3200, or even higher, the Foveon sensor is best at lower ISOs. It is usable to about ISO 400 and then noise climbs rapidly as the ISO increases. The latest SD14 Foveon is reported to be better in ISO sensitivity, but it still falls far short of the extended ISO performance of its competition.

The other major issue with the Foveon sensor is that the separation into 3 distinct colors for each pixel site is not nearly as straightforward as Foveon describes it.  The captured image still requires a lot of image processing to extract the 3 colors from each pixel site and reconstruct the finished image.  In fact some critics claim the image processing required by the Foveon sensor is even more extensive than Bayer Array demosaicing.  The purer the data in any extraction process the more faithful it is to the original capture, so the Foveon sensor may offer fewer "post-processing" advantages than it first appears.  When conditions and lighting are correct the Foveon can deliver stunning images, but things in photography are rarely perfect.

For the purpose of our discussion the Foveon is more a novelty than a sensor you will likely use today. Despite its limited availability, however, the concept of the Foveon sensor is as compelling as ever, and you can actually buy a production camera, the Sigma SD14, that uses this sensor. As you can see from the specs, the sensor size is 20.7x13.8mm, which places the Foveon between the Canon small APS C and the Olympus 4/3 sensor. The lens multiplier is 1.7X.

Field of View

Now that you have some basic understanding of digital camera sensors, it is time to take a closer look at the practical considerations that are created by these differences in sensors. A very poorly understood concept is the lens multiplier with the smaller than 35mm sensor-size that is used in most digital SLR cameras. The best way to illustrate this is with actual photos taken by a range of digital SLR cameras from the same tripod location.

We shot the same view using the exact same tripod location on a range of current digital SLR cameras. Each camera used a lens with the same focal length of 50mm. Lighting was the same with a 100W high-right light source, camera aperture was f4.0 in all cases, and white balance was set to Tungsten. The purpose of this series is to illustrate what you can see with each camera with the same lens, so exposure data is somewhat irrelevant, but exposure conditions were kept as constant as possible for reference.

The Canon EOS 5D is a full-frame SLR, which means the sensor is the same size as 35mm film. This point of view is the way an image at this distance would look on the Nikon D3, Canon 1Ds III, Canon 5D, and 35mm film cameras. The APS-H sensor used in a few Canon pro models is 1.3X and falls between full frame and 1.5X in its field of view.

Lens Equivalence

It is important to understand that a 50mm lens is always a 50mm lens, as that is the focal length. That 50mm specification affects depth-of-field and other image characteristics tied to the lens focal length. However, we can calculate focal lengths for each multiplier that will give the same field of view in the finished image.

With a closer look at field of view and the impact of the changes in field of view, it is easier to understand recent DSLR lens developments. Early DSLR lenses were generally 35mm lenses mounted on the new smaller sensor cameras, except for complete new systems such as the 4/3 digital-only system championed by Olympus.

Using 35mm or full frame lenses was great if your primary interest was telephoto and bird photography, as that 35mm 70-300mm lens that was the second lens for most film buyers now had a field of view like a 112mm-480mm zoom on the new Canon Digital Rebel. Unfortunately interiors, architectural photography, scenes, and fans of the extreme wide angle point of view were left in the cold in the early transition to small digital sensors.

That has been corrected in recent years with lenses designed for smaller sensors, lenses like the Canon 10-22mm, the Nikon 12-24mm, and similar APS C zooms from Sigma, Tamron, and Tokina. Today, whatever your mount and lens multiplier, there are lens choices that can cover the full range of choices for field of view.

A few lenses by Sigma are actually available in every mount and multiplier listed above. Obviously, these few lenses were originally full-frame 35mm that have been carried over with new coatings for improved performance and reduced flare on digital sensor SLRs. One such lens is the Sigma 24mm f1.8. The field of view on the different mounts and sensors this lens will fit illustrates just how the digital sensor size can influence the use of any lens. On the full-frame Canon5D, IDs III, and Nikon D3 this lens is a fast super wide 24mm. On the Canon 1.3X pro models it is still a fast f1.8, but with the FOV of a 31mm moderate wide angle.

On the Nikon D300/D60, the Sony A700/A350, and the Pentax K20D/K200D this fast lens is now a moderate wide angle to near normal lens that shoots images with a 36mm angle of view. On the Canon XSi and 40D we are at 38mm, which most would consider near normal. The Sigma SD14 FOV of 41mm has definitely crept into the normal range. Finally the 4/3 mount version of this lens is one of the "normal" lens choices on the Olympus E3/E510/E410 and Panasonic and Leica 4/3 digital SLR cameras. The 24mm on a 4/3 camera looks at the world as though it is a 48mm f1.8 lens, and competes with the Leica 25mm f1.4 as a much lower cost normal lens.

Similar comparisons could be made in other focal length ranges, but you get the point. Olympus makes a 70-300mm telephoto lens for 4/3, and it is much sought after by "birders", because the view on a 4/3 camera with this lens extends from 140mm to 600mm.

Fast Forward

With digital SLR sales continuing to show record growth in a photographic market whose overall growth is much slower, it should be clear that a lot of photo buyers are selecting digital SLR cameras instead. The reasons many of these new buyers select a digital SLR is because they want better quality pictures than they can get with a point and shoot camera. They may also choose a DSLR for the flexibility and growth potential if they get hooked on the photo hobby.

These are exactly the same reasons buyers chose film SLRs instead of 110 point and shoots in the 70s, and 80s. Those reasons are just as valid in the DSLR market as they were in film, and maybe even more so. Digital sensors, like other electronics, are constantly evolving and improving, and whatever megapixel assumptions we talk about today will certainly become invalid and outdated in the near future. However, it is very clear with today's sensors that the tiny sensors in compact point-and-shoot cameras are reaching the point where higher resolutions are simply being traded for noise. Somewhere around 8-10MP we are finding that higher resolution also generally means higher noise and lower sensitivity.

No doubt this roadblock will be passed with advancements in sensor technology, but today more than 8MP of clean resolution and usable sensitivities greater than ISO 400 are rare indeed in the compact camera market. APS C sensors in digital SLRs, however, seem to be getting better and better at higher and higher sensitivities at ever-increasing resolutions. Pundits are already screaming we are going too far with14MP sensors, but they forget that the smallest 4/3 sensor is still more than nine times greater area than the average compact sensor. There is still a lot of room for growth in resolution.

The other complaint - that lenses are finally reaching resolving limits with higher sensor resolutions - is certainly true with the cheap lenses that were the wunderkind of the developing SLR market. It looks like time for quality optics again as the industry has been skating for far too long in the low demands of the developing digital SLR market.

It also appears that prosumers, the serious amateurs among us, will be facing a difficult decision today and even more so in the near future. The cost of larger and larger sensors has been dropping rapidly, and CMOS sensor development from all the majors is also a factor in lowering costs and increasing resolution. Like it or not Canon and Nikon have already begun segmenting their SLR line into full-frame and APS C sensors. Those who couldn't figure out why Sony was introducing mainly full-frame lenses will finally get their answer later this year with Sony's 24.6MP full-frame flagship model.

Despite the fact that full-frame will be aimed at the top of the DSLR market by Canon/Nikon/Sony, the APS C market does not appear to be in any danger. Developments and new models will definitely continue. Players like Pentax and Samsung seem positively locked into the APS C space with no full-frame peeking around the corner, and Olympus has fought too hard for credibility with 4/3 to start singing a full-frame song. Similarly Nikon, Canon, and Sony will adamantly define the full-frame as pro and the rest of their line as prosumer and entry-level. Nikon may also have struck the marketing chord that will develop with full-frame sensors being touted more for their incredible range of ISO sensitivity than for their higher megapixel resolutions.

The problem is that prosumers lust after pro gear and a prosumer today will have to ask another question in their buying decision for accessories now that full-frame looks like it will be "for real". That question is: "will it work on a full-frame". The current $2000 street price of the Canon 5D and the coming release of the Canon 5D Mark II are making that question an important one for many prosumer buyers. The final street price of the presumer Sony "A900" is also still a mystery, but if it is in line with the Canon 5D, as many expect, then this question in the back of the minds of prosumers will move up-front very quickly.

The purpose of this sensor guide was not to explore every facet of sensor design and performance considerations. Each topic discussed could have been an individual article in its own right with more in-depth discussion of the factors that drive design decisions. Instead, the hope was to provide a framework of basic sensor information to provide a better understanding of the evolution of digital sensors and the types of concerns and decisions that are being made in the market today. We sincerely hope you come away with a better understanding and appreciation of the current digital SLR market, and perhaps of your own digital SLR camera or one you might buy in the future.

Part 2 of this Sensor Series is in the works and many of the images are already in the can. It will take a closer look at the sensitivity range and noise of the most recent sensors in the 14MP, 12MP, and 10MP classes of sensors. A few more cameras are on the way, and as soon as they are prepped and tested we will be sharing more of our findings on the newest sensors in the higher resolution sensor classes.