Original Link: https://www.anandtech.com/show/2529



In The Digital Sensor: A Guide to Understanding Digital Cameras the history and development of the Digital Sensor was explored. First up was exploring how analog sensors in digital cameras work. By taking a closer look at how the digital sensor evolved we could better understand how APS-C Digital SLR sensors got started and grew to dominate the current DSLR landscape. This led to a discussion and examples of what the lens sees (Field of View) with full-frame (1X), 1.5X, 1.6X, 1.7X, and 2X DSLR sensors.


Part 1 then covered the technology of current sensors with a closer look at Bayer (and related Fuji Super CCD) and Foveon sensors. Finally, the current move to CMOS sensors from CCD sensors was explored by looking at the advantages and disadvantages of each sensor type and the role of the supporting analog-to-digital chips required in each design.

With this knowledge of digital camera sensors and how they capture images, Part 2 will take a brief look at how captured pixels are then converted to a usable image. This will examine how in-camera processing works to produce JPEG files. The advantages and disadvantages of the alternative RAW image capture with post processing is also explored.


This installment will then take a closer look at current DSLR camera sensors and how they perform as finished products. We will compare images with a cross-section of current DSLR cameras at 10MP, 12MP, and 14MP resolutions.



How a Digital Image File is Created

In Part 1 of The Digital Sensor the basics were presented of how the digital image data is captured with an analog sensor using a Bayer array. As mentioned in the first part, the mosaics of the three colors are reassembled into an image in a process called demosaicing. Of course, that is only the starting point for creating a usable image from a capture of color bits with an analog sensor.


The process of demosaicing includes interpreting Bayer array data and converting it into an image with three colors for each pixel. During this step the camera also applies white balance - to make the image color appear "correct" under the lighting used when the image was captured.

Digital sensors "see" differences in light linearly, so that twice the light intensity produces twice the response in the sensor. Our eyes, on the other hand, see light logarithmically. So when light intensity quadruples the eye perceives this as a doubling of light. The camera takes this into account by applying tone curves to the image in the conversion process.

In the above example we have gone from the pixilated Bayer array with a typical green tint to a dark reconstructed color image to a brighter finished image. Contrast, color saturation, and sharpening may also be applied in this step, depending on what is selected in the camera. Finally the high bit-depth RAW image is then converted into 8-bits per channel and compressed into a JPEG based on the compression settings chosen or used by default in your camera. All of the processing up to this point has likely taken place with the image in the camera buffer.

One of the problems with traditional photographers moving to digital is that they really don't understand that a digital camera is little more than an image processing computer with an optic attached that spits out a compressed standard format JPEG image file. With that understanding it is easy to see where RAW images might be an advantage in some situations.

All that goes on in the computer (camera) takes control away from the photographer. Those that prefer total control over their final image, including tricks learned over many years in the darkroom, often prefer to control the conversion process themselves. The argument goes that image control is part of what makes a person a photographer, and that digital is like a trained monkey pointing and clicking. Other photographers who sing the praises of digital see it as liberating, freeing them to concentrate on their unique photographic "vision".

Most serious cameras provide users a choice. The great majority of users, and virtually all casual users of DSLRs, shoot and use the JPEG images processed by the camera they are using. They choose to trust the camera manufacturer to make useful decisions in the conversion process. In fairness it should also be pointed out that most serious cameras allow immense control over the choices made for in-camera processing. Those who want control can often customize and fine-tune the in-camera processing to deliver the kind of image they choose.

Those who want full control over the conversion process may choose to shoot RAW and make their own decisions about what software to use, the conversion "work-flow", and the parameters important to them in the finished image. This photographer is more often a professional, but with the cheap cost of computer processing power these days, it is also a real option for photo amateurs and hobbyists.



JPEG vs. RAW

One of the ongoing arguments among photo enthusiasts is whether to shoot RAW or JPEG. Since you now understand how a digital camera captures these RAW and processed images, it is reasonable to talk about the advantages and disadvantages of each format.

The native format for most DSLR cameras is JPEG. This is the file format every computer recognizes, the one you see on the web, the file format that is all but universal for saving graphics files. JPEG is a compressed file format, however, and some tools like Photoshop (and even some DSLRs' internal processing) allow varying compression algorithms to improve resolution (larger file size) or create a smaller file (less resolution).


JPEG stands for "Joint Photographic Expert Group" and it is a compression standard developed specifically for photographs. However, anyone who has worked with compression algorithms, even very good ones, soon realizes the greater the compression the more likely details (resolution) will be lost. That is one reason most serious cameras offer varying levels of JPEG compression, so the end user can choose between file size and resolution. Also, like any other compression scheme, some subjects, as you see above, are better suited for compression than others.

This tradeoff between compression and file size mattered a great deal when flash memory was very expensive. Today's cheap flash memory, however, has made these kinds of compromises almost a moot point. Today you can buy huge flash cards at relatively cheap prices so there is no longer much justification for heavy compression choices to save flash memory. The other reason - faster in-camera image processing - still matters, but the rapidly improving camera computing power is also making that less important than it was just a couple of years ago.

The JPEG file is what is saved after the camera has processed a digital image. This is after the cameras have applied whatever corrections, enhancements, color balance and noise reduction schemes the camera maker believes improve the image. This is not an exact art and camera makers have different ideas about what constitutes a "good" image. The camera manufacturers also tend to vary in their ability to achieve certain results in the design of their image processing electronics in the camera.

You will see heated arguments on photography forums and page after of page of review coverage at photo sites on the success or lack of success of a particular camera's JPEG processing. This is akin to arguing about the merits of a friend's personality and the beauty or ugliness depends on who is talking. The same is true of the various photo sites as they also have their own very strong ideas of what is "right" and what is "wrong" in JPEG processing.

Most "serious" cameras also can capture images in RAW mode. RAW is supposed to be the unprocessed and unmanipulated image - the digital equivalent of a negative. On the surface this sounds like we should always compare RAW files, as this removes the post-processing and looks only at the capture abilities of the sensor. It would be very nice if things were that simple, but they aren't.

First of all there is currently no standard for how RAW images are created and saved. This is proprietary to each individual camera maker. This is important because you cannot even view a RAW image unless the software you are using supports that camera's RAW storage format. To complicate this further RAW formats even vary among models from a single camera maker.

Adobe is trying to standardize RAW with a format called DNG or Digital Negative. It's a great idea and Adobe has added the capability to convert and save RAW formats it recognizes into DNG format in their Photoshop programs. Ideally cameras would capture DNG as a standard format, but camera manufacturers like Canon and Nikon do not easily give up proprietary advantages they believe they have in their own formats. Thus far the only camera maker who offers DNG capture as a RAW option is Pentax.

RAW also ignores a large part of what we are paying for when we buy a DSLR. The user is buying a computer to capture and process digital images. It is much easier and cheaper to design a camera that only captures RAW and leaves the processing to a computer program. A good example of that is the Sigma Foveon-sensor DSLRs. Until the recent models like the SD14 the cameras only captured RAW. It was much cheaper to design and manufacture the electronics for RAW capture only. It also required much less processing power if the comparison were apples-to-apples.

Unfortunately the Foveon example was more complicated than this surface analysis. The reality is that the Foveon sensor required a lot of processing power just to separate the three colors it "captured" natively with the Foveon sensor. There was only so much processing power available to do in-camera work, and this was also part of the reason conversion to JPEG got moved to the computer until the recent models. However, the fact remains that a camera that just captures RAW is much cheaper and simpler to build that one with powerful in-camera processing for JPEGs.



Technical Advantages of RAW and JPEG

Other than enhanced control over the process are there technical reasons for shooting RAW instead? A few years ago we would have proclaimed a resounding "Yes" to answer this question. Demosacing requires a lot of processing power, and just a few years ago you could easily demonstrate that RAW shooting and computer processing provided higher resolution images than those that could be produced "in-camera".

The answer to this question today is not as clear. With each generation of new cameras that truth becomes less the case. DSLR processing power has been growing by leaps and bounds, and we have now reached the point where JPEG images from the Nikon D300 and Olympus E-3, for example, actually test higher resolution that the RAW images they capture. Processing power continues to get cheaper every day and this old argument for RAW instead for highest resolution is disappearing as processing power and in-camera software sophistication continue to grow.


One area where RAW still has tremendous value is the area of white balance control. Despite the phenomenal improvement in digital imaging overall, auto white balance still seems a mystery function in many of the latest DSLR cameras. White balance is part of the JPEG processing and it is often difficult to precisely adjust White Balance in a JPEG after the fact. With RAW images, however, correcting White Balance or completely shifting it for creative impact is a very easy task in most RAW software like Adobe Photoshop RAW.

One very significant drawback of RAW is that the quality of RAW conversion is totally dependent on the software that is used for RAW conversion. Many programs are too "universal" in scope to squeeze the most from any particular camera's RAW images. Other programs are closely tied to a particular camera (like those that come with DSLR cameras) and this "home-grown" software is sometimes lacking in options and image-processing sophistication. RAW processing software is definitely improving and the trend line is clearly toward better and more useful solutions.

The other huge disadvantage of shooting RAW is time. A JPEG file is immediately ready to use in some form; a RAW file requires some post-processing to even see the image.

Many pros and hobbyists shoot JPEG + RAW when results are crucial. This allows the option of the easy to use JPEG when it gives the photographer what they need and the RAW image for thoughtful manipulation when the JPEG fails to deliver the result or the photographer wants more control over the finished image.

While processing power is growing rapidly in digital cameras it is still true that the digital camera is not nearly as powerful as a computer as your desktop or notebook computer. Thus the digital camera makes compromises to speed processing and image conversion that might not be made if more processing power were available. This is both a negative as well as a plus. You can be sure that the in-camera processing is very efficient and specifically tailored to your sensor and possibly your lens if the lens contains a ROM (like all Olympus lenses and many other electronic lenses from other makers). The desktop computer definitely has more power, but image processing from RAW means the conversion is still dependent on the quality and flexibility of the software used for that conversion process.



Raw Examples

While RAW can offer greater creative control for the photographer, the additional time required for conversion of a RAW file to a usable image and the storage requirements for RAW and loss-less compression files will keep most from routinely shooting RAW instead of JPEG. However shooting RAW is an option in almost every DSLR camera. It is there when you need it.

In addition to the limits of in-camera processing, the common JPEG file is also compressed. Compression can be adjusted in most cameras from an option with the least compression and highest quality and largest file size (Maximum JPEG or 100%) to the greatest compression and poorest quality and smallest files size (Low or 10%). When shooting and processing RAW, the RAW file can be processed and saved as a lossless TIFF (tagged Imaged File Format) file with no compression at all if you choose.  For web publishing there is also saving as a PNG file, which is another loss-less file format.

While lossless sounds good the storage requirements and overheard for processing can become huge. In the samples below with the 14.6MP Pentax K20D, saving a RAW file in the Pentax standard PEF format creates a file size of 14.3 to 21.5MB. Processing the RAW PEF and saving a single full image as a lossless TIFF generates files that are 45MB for each image. Applying minimal LZW compression to the TIFF can reduce the size to 35MB and using ZIP compression in the TIFF processing can yield a 30MB file. This compares to the highest level JPEG files produced in the camera that are 11 to 12MB.

The samples below compare JPEG and RAW-processed images from the Pentax K20D. This camera was chosen as an example because it is the largest consumer-priced sensor currently on the market. In addition many reviewers complain about Pentax JPEG processing and recommend capturing images with this camera in RAW for highest resolution. Several review sites have found the K20D in RAW mode to offer the highest resolution available on any consumer DSLR.

The RAW processing consisted of converting the files from RAW to JPEG using Camera RAW in Photoshop CS3. No processing or adjustments at all were used in processing the RAW files. Since all images were captured using the Tungsten preset it was interesting to see that the RAW files "As Shot" by the Pentax were 2500°K instead of the 2850°K usually seen as the Tungsten preset definition in most cameras. This could be easily adjusted, as can sharpness and every other parameter you wish to control in RAW. That is an option that was not used for this demonstration.

Crops were captured directly from the RAW image and saved as a ZIP compressed TIFF for a moderate size and minimal compression. The hope was to provide uncompressed TIFF files for the RAW viewing, but at 45MB per image there were concerns the AnandTech server could handle the traffic. For these samples the RAW file was saved as a Maximum Quality 100% JPEG. It is interesting how much file size an be reduced when you select little to no parameter adjustment, no sharpening, and no noise reduction. The 100% JPEGS produced in the RAW conversion were 2.4 to 7.5MB, which is much smaller than the in-camera processed Maximum JPEGS.

JPEG and RAW Comparison
Pentax K20D (14.6MP)
ISO JPEG
(Highest Resolution, In-Camera)
RAW
(PEF saved as Maximum JPEG)
100
200
400
800
1600
3200
6400

Click on any of the above image crops for the full image.
Note: Full size images are between 9.8MB and 28.5MB!


The in-camera JPEG processing applies additional sharpening and some noise reduction. We had the in-camera noise reduction ON but at the lowest selectable level available. With RAW processing you can choose the degree of sharpening, color saturation, noise reduction, etc. that you prefer and automate that conversion process after you shoot the RAW image - all in your computer. However, where the camera processing is dependent on the image processing preferences of the camera designer, the RAW processing is very dependent on the RAW conversion software you use. The decision is who you trust most with your image.

RAW is a very useful tool for some professional photographers who want complete and total control over the image creation and conversion process. Those who lived for the darkroom will likely only shoot in RAW and RAW conversion is the Digital-Era equivalent of the film darkroom. RAW conversion is powerful but it can also be very time-consuming.


Having said that, one area where RAW conversion does shine is White Balance control. With all the sophisticated processing capabilities in today's DSLRs it is amazing that none of the manufacturers have figured out how to get Auto White Balance to work acceptably under Tungsten or Fluorescent light - the two types of lighting you will most likely find in homes and commercial space. Shooting RAW you can quickly and easily adjust white balance just by selecting a drop-down description or fine-tuning a Kelvin temperature slider.

If the camera processing is fast enough many experienced photographers shoot RAW+JPEG. In most situations they will use the JPEG file, but when extra control is needed, or the in-camera processing just isn't up to the photographer's preferences, the RAW file is available for custom control. This can slow lesser cameras down considerably, so consider the advantages and disadvantages before you jump on this bandwagon.

In the end use RAW when you want ultimate control over the image processing and you know how to manipulate RAW files in software you trust for this process. At the very least you can do some simple RAW capture and conversion in tricky lighting situations using the RAW converter that came with your camera or a simple program like Photoshop Elements which supports the latest Adobe Camera RAW just like Photoshop CS3 does.

For future reviews images will generally be JPEG with in-camera processing. That is the way most of our readers will use these cameras. There is no pretense here that AnandTech is serving a professional photography market that lives for the creative control of RAW processing.

With the meteoric rise in DSLR sales we believe the great majority of these new buyers are photo hobbyists and not advanced amateurs or professionals. They buy a Canon or Nikon or Sony or Olympus or Pentax or whatever camera for the quality of images the camera produces. That includes the in-camera image processing that goes on to produce a JPEG saved to the memory card. The bulk of these new buyers may be interested to know that the Pentax has higher resolution when images are captured in RAW, but mostly they will shoot default finished JPG images.

You should know that RAW is an extremely powerful tool if you know how to use it, and frankly you can do some incredible things in RAW with little knowledge of all the parameters. The important thing is the option of shooting RAW or RAW+JPG is available on almost any DSLR. You should choose to use it and learn a little in difficult lighting or in situations where you have a "mind's-eye" picture that you want to create in the digital darkroom that is RAW processing.



10 Megapixel Cameras

10MP seems to be the minimum resolution for today's newest DSLR cameras. However, this does not mean that 10MP is entry level. Recent 10MP models include the Prosumer Canon 40D and the "Pro" Olympus E-3, as well as the entry Nikon D60, Olympus E420/E520 and Pentax K200D, and mid-level Panasonic L10 and Canon XTi. The four cameras here represent a cross-section of 10MP models, including a 1.5X, 1.6X, and two 2X (4/3) sensors. The Nikon D60 uses an older Sony CCD sensor and the other three models are CMOS technology.

Wherever possible the images were captured using a 50mm f/1.4 normal lens. This represents an equivalent 35mm focal length of 75mm for the Nikon D60, and 80mm for the Canon 40D. A 50mm on the 4/3 cameras would have an equivalent 100mm field-of-view so images were captured using the 35mm Olympus Macro lens, which is equivalent to 70mm. This lens was chosen because it is critically sharp wide-open and is in its best resolution range at the standard f/4.0 capture aperture.

All images were captured at the same f/4.0 aperture using a tripod in the same location. Focus was manual and the camera program selected the shutter speed. Lighting was a single 100-watt Tungsten bulb high right, and all cameras were set to the Tungsten preset.

10MP Sensor Performance
JPEG Comparison over ISO Range
ISO Nikon D60 Panasonic L10 Canon 40D Olympus E3
100
200
400
800
1600
3200  

Click on any of the above image crops for the full image.
Note: Full size images are between 3.1MB and 5.4MB!


Up to ISO 800 all four cameras are very similar in their resolution capabilities.  One camera that stands out, however, is the Panasonic L10, which exhibits more "punch" with standard in-camera processing.  However the extra sharpening and more vivid colors trade off noise as we are already seeing noise at ISO 800 along with the very sharpened image.  This may have more to do with the target market of current point-and-shoot users than anything else.  The E-3 is also a 4/3 sensor, but its rendering is more comparable to the Canon 40D, so the L10 performance cannot be attributed to the sensor alone.

You can also clearly see the differing approaches to image processing among the four camera makers.  Some move toward a softer edge for a much smoother and less noisy appearance, and others go for sharp.  The above images are default with the lowest selectable level of noise reduction.  However, the appearance of the finished JPEG can be varied in all the cameras by selecting different sharpening, noise reduction color saturation, etc. in the menus for camera settings.  You can set up the look to generally match what you prefer in you pictures.

By ISO 1600 the consumer cameras – the D60 and L10 – are starting to show the demands of much higher speed with increased noise. However the prosumer 40D and E3, even though they use different size sensors, are both holding up very well. By ISO 3200 you can clearly see the different approaches to sharpening and noise between the Canon and Olympus, which both use a CMOS sensor.



12 Megapixel Cameras

12MP seems to be the resolution of choice for recent high-end or "serious" DSLR cameras. Again, the actual cross-section at 12MP represents a much wider range of models than you might imagine. The Sony CMOS image sensor, used in the top Sony A700 and the "Pro" Nikon D300, basically set 12MP as the next resolution class. However, the 12MP class also includes the mid-entry level Canon XSi and the 2+ year old full-frame Canon 5D.

Now that the Canon 5D is selling for just a little more than the Nikon D300 and Olympus E-3 you have to consider the 5D in a comparison of prosumer cameras. With the $300 Instant Rebates on the 5D that started in the US today the 5D will probably be even less expensive. It is due for replacement this year but it is still very competitive and some would consider it the best available at its current price point.

The four cameras here represent the 12MP models, including two 1.5X, a 1.6X, and one 1X (full-frame) sensors. All sensors in these four cameras are CMOS, which seems to be the trend for new sensors for reasons discussed in Part 1 of The Digital Sensor.

All images were captured using the manufacturers' 50mm f/1.4 normal lens. This represents an equivalent 35mm focal length of 75mm for the Nikon D300 and Sony A700. The Canon XSi equivalent is 80mm. The full-frame Canon 5D equivalent is the specified 50mm. The distance to the subject was reduced when using the Canon 5D so that the captured image was about the same field of view as the crop-sensor cameras. With the 50mm FOV on the 5D much more of the scene is captured at the same shooting distance than with the crop-sensor cameras.

All images were captured at the same f/4.0 aperture using a tripod in the same location except for the full-frame 5D. Focus was manual and the camera program selected the shutter speed. Lighting was a single 100-watt Tungsten bulb high right, and all cameras were set to the Tungsten preset.

12MP Sensor Performance
JPEG Comparison over ISO Range
ISO Canon XSi Nikon D300 Sony A700 Canon 5D
(Full-Frame)
100
200
400
800
1600
3200  
6400    

Click on any of the above image crops for the full image.
Note: Full size images are between 3.9MB and 11.4MB!


12 Megapixel sensors seem to be the hot competition arena in current DSLRs, and it certainly shows in the very different approaches to in-camera processing shown in the JPEGS from these four cameras. You should take a close look at the Sony A700 and Nikon D300 results since they are based on the same sensor. The impact of in-camera processing on the finished JPEG can’t be illustrated more clearly than by comparing the Sony and Nikon images.

You should also pixel peep the images from the full-frame Canon 5D and compare them to the Nikon and Sony. You will probably find a smaller difference in image quality than you expected, which just demonstrates how much progress has been made in sensor technology since the Canon 5D was introduced more than two years ago. The successor to the 5D is expected later this year and it is rumored to feature a 16 megapixel full-frame sensor.



14 Megapixel Cameras

The 14.6MP Pentax K20D is the highest resolution sensor available in a prosumer camera today. Certainly there are pro models at $8000 or more than feature even higher resolutions, but the $1299 MSRP K20D is a long way from that price class. When it was introduced in late 2007 the K20D was the first 14MP class camera, and its introduction surprised the photo establishment with a Pentax-designed and Samsung-manufactured CMOS sensor.

Several months later Sony introduced the mid-level A350 with a 14.2MP CCD sensor. The Sony CCD is unusual in that it is the only recent new sensor introduction that is not based on CMOS technology. Again, more megapixels does not necessarily mean the DSLR is targeted at the prosumer user. The K20D certainly aims there, but the A350 is a much more basic camera with a uniquely easy-to-use full-time Live View mode designed to appeal to those moving up from point-and-shoot and those who appreciate ease of operation. There are two models below the A350 - the A300 and A200 - so the A350 is a solid mid-level DSLR much like the Canon XSi.

Both the Pentax K20D and the Sony A350 are 1.5X crop sensor, which with the 50mm lens is equivalent to 75mm in 35mm terms. All images were captured at the same f/4.0 aperture using a tripod in the same location. Focus was manual and the camera program selected the shutter speed. Lighting was a single 100-watt Tungsten bulb high right, and all cameras were set to the Tungsten preset.

14MP Sensor Performance
JPEG Comparison over ISO Range
ISO Pentax K20D Sony A350
100
200
400
800
1600
3200
6400  

Click on any of the above image crops for the full image.
Note: Full size images are between 4.2MB and 11.8MB!


The Pentax K20D is the first camera to use the Pentax-designed and Samsung-manufactured 14.6 Megapixel CMOS sensor. As pointed out in Part 1 of The Digital Sensor Sony and Samsung share several patents for CMOS manufacturing which explains why the new Samsung sensor suddenly appeared on the scene.  It did not just pop out of nowhere but had been in development for some time.

Some other reviews have found the new Pentax/Samsung sensor to exhibit the highest sensor resolution in its class, but some also complain about Pentax in-camera processing decisions and they advocate shooting this camera RAW. Our personal experience has been that color can be very strange sometimes on this 14.6MP sensor. The DNG option is so very off in color in Photoshop CS3 as to be almost useless at higher ISO speeds. If used with the software tools that come with the K20D or with PEF RAW processing in Photoshop CS3 it is possible to get impressive results. However, this sensor requires more care to extract top performance than the Nikon D300, for example.

If you wondered why Sony put the 14.2 megapixel CCD sensor in the mid-level A350 instead of their top model the samples here should shed some light on the answer. Sony has used heavy sharpening and noise reduction to get the most from this sensor at higher speeds. This suits a consumer-level DSLR just fine and there are no real issues up to about ISO 800. However, the heavy noise reduction used at higher ISO speeds with this new sensor would not likely be as well-received in a prosumer or semi-Pro model.  It is still not clear if this beefed up noise reduction is necessary due to the noise generated by the smaller pixels of this 14.2MP CCD sensor or whether the post-processing is more Sony's view of what would appeal to the target market for the A350.  More time with this new sensor may answer this question. 



Fast Forward

There was a time not long ago when casual photographers selected a point-and-shoot digital camera. They were reasonably priced, new models were everywhere, and the price for something even better was extremely high. Technology development in the digital camera arena, as in every other area of consumer electronics, has pushed the price of digital sensor technology lower and lower, and that is a trend that will undoubtedly continue. At the same time speed and quality have continued to evolve at a dramatic pace.

As a result the digital point-and-shoot has moved downstream, as it is hard to convince anyone to buy an expensive point-and-shoot when you can buy a capable Digital SLR today for as little as $400. When 10MP sensors burst onto the DSLR scene about two years ago the price of admission was $1000. Today that $400 to $600 DSLR has a 10MP sensor.

With lower prices and more capabilities, the Digital SLR is clearly today's photo market leader. The explosive growth in this segment is bringing new first time buyers into the DSLR market, some moving up from point-and-shoot and some choosing one of today's more reasonable DSLRs as their first camera.

With so many new users in the DSLR market it should come as no surprise that DSLR makers are trying to make DSLRs easier to use. There is one trend to make the DSLR more comfortable for those moving up from point-and-shoot with features they already know like Live View. Another trend is to give first time users a greater chance of success by combining optical (in-lens) or mechanical (in-body) IS (Image Stabilization) with the cheaper, slower DSLR lenses. This actually gives new users a better chance of capturing decent pictures in everyday lighting conditions. If you wonder how universal this has become you only need to look at the cheap optical IS lenses Canon and Nikon now supply with their entry D60 and XSi models.

It is easy in examining technology to forget about buying motivations. Lower price is increasing Digital SLR demand, but the reason new buyers select a Digital SLR is because they want better quality pictures than they can get with a point-and-shoot camera. The same reason applied in the first SLR explosion in the 70’s and 80’s when new buyers chose film SLRs instead of 110 point-and-shoots. 

The quest for improved quality may be even more relevant in the digital camera era than it was in film. Film was a common denominator in film cameras, but in digital cameras film and the processing lab have moved inside the camera. This makes the digital sensor the most important factor in the imaging quality of today’s digital cameras. Different manufacturers have different optic lines to mount on this analog-to-digital computer. All the big brands have different expertise and interpretations of the analogue capture to digital image conversion process. In the end, however, it all begins with the digital sensor. 

The digital sensor is the reason the tiny sensor in point-and-shoot cameras has a limited speed range and why the images can never be as good as a Digital SLR. Even if you mount the world’s best optics on a point and shoot you are still quality bound by the digital sensor capabilities. For today the resolution limits of the small P&S sensors seem to have been reached. Somewhere around 8 to 10MP we are finding that higher resolution also generally means higher noise and lower sensitivity. That is the reason the growth and development has moved to the larger sensors of the DSLR.

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 and ever increasing resolutions. Skeptics are already screaming we are going too far with14MP sensors, but they forget that the smallest 4/3 sensor is still a ten times larger area than the largest compact sensor. There is still a lot of room for growth in resolution.

The other complaint you often hear is that lenses are finally reaching resolving limits with higher sensor resolutions. That is certainly true with the cheap lenses that were the staple of the developing SLR market. Most any piece of glass was fine on a 6MP sensor, but 12 to 14 megapixels demand quality optics. This will challenge the industry to produce higher resolving optics at ever cheaper prices as digital cameras approach and pass the resolving power of 35mm film. The industry has been coasting for far too long in the low demands of the developing digital SLR market. Innovative high-quality optics will emerge as we are already seeing in some of the remarkable new kit lenses developed for the higher resolution sensors.

Serious photo hobbyists will also be facing difficult decisions 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 sensor manufacturers is also a factor in lowering costs and increasing resolution. Like it or not Canon and Nikon have already begun segregating their SLR line into full-frame and APS-C sensors. Those who wondered  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.

Full-frame has been mainly the domain of Professional photographers up to this point. Full-frame will likely still be targeted at the top of the digital SLR market by Canon/Nikon/Sony so your favorite APS-C camera and lenses does not appear to be in any real danger of becoming obsolete.

Players like Pentax and Samsung seem positively locked into APS-C with no full-frame peeking around the corner, and Olympus has fought too hard for credibility with 4/3 to start promoting full-frame. Similarly Nikon, Canon, and Sony will define the full-frame as Pro and the rest of their line as prosumer and entry. However, technology will march on and new and cheaper full-frame sensors will be introduced. With the new sensors will come new camera models built around those sensors.

Those who doubt that only have to look back at the development history of the digital sensor. When 1 megapixel was reached Nikon ran huge spreads of carefully produced photos created with their expensive point-and-shoot digitals showing that digital had arrived and photographers had all they could possibly need in that 1 megapixel sensor. We know better today only because the digital sensor continued its development.   You can be certain that, like CPUs in computers, the digital sensor of tomorrow will be different in ways we can only imagine today.  

For some readers the joy of the process is the technology ride. For others the utility of the ever evolving digital sensor and processing electronics is the main thrust. We can only say there is plenty of joy in the Digital SLR market for everyone. 

Slapping optics on an Analog-to-Digital imaging computer is an exciting concept for geeks. We sincerely hope The Digital Sensor articles have given you more insight into how digital cameras work and a better understanding of the technology issues facing Digital Camera development.

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