The digital camera industry is heavily invested in the concept of megapixels, where one megapixel = one million pixels. One can define the number of megapixels based on the number of pixels in the camera sensor, or one can define the number based on the number of pixels in the resulting image. With nearly all cameras, there is no substantial difference between the two. For example, Canon's flagship compact digital camera, the Powershot G9, has a sensor made up of 12 million pixels in a single layer and outputs a final image that is 4000 pixels by 3000 pixels (12MP). The Foveon X3 sensor in the Sigma DP1 and SD14 is an exception. This sensor uses three layers of pixels with 4.6 million pixels in each layer. While that means that there are roughly 14 million pixels altogether in the sensor, the output of this sensor is an image measuring 2640 pixels by 1760 pixels (4.6MP). Sigma and Foveon detractors have pointed out the obvious discrepancy here. Clearly a 4.6MP output image cannot contain 14MP of detail. For essentially marketing reasons, Sigma is referring to the DP1 as a 14MP camera. After all, who would pay $1000 ($800 street) for a 4.6MP pocket camera?

As it turns out, Sigma is forcing us to re-evaluate megapixel ratings just as AMD forced us to re-evaluate gigahertz ratings in the computer processor industry. Not all megapixels are created equal from a detail standpoint, and that's without even considering other aspects of image quality including color fidelity, noise, and dynamic range. Anyone who's ever put a mediocre lens on a good DSLR can tell you that to do so is to literally throw away megapixels. In fact, it takes a very good lens to fully utilize the resolving ability of a sensor across the entire frame. Assuming one has such a good lens on hand, the next issue is whether the sensor itself can deliver in terms of "per pixel sharpness." For technical reasons that are well explained elsewhere, the sensors used in most cameras simply don't deliver as much detail as their megapixel ratings imply. Without delving into the reasons for this, it is easy to recognize the issue. View any image from a high megapixel camera on screen at 100%, and one can see that the level of detail simply isn't as high as it is in a resized image. At their "per pixel level," these images are just a little bit blurry. Typically speaking, one has to resize the image to 75% or less and then sharpen before the apparent detail is truly crisp. On average, this resizing step corresponds to an approximately 50% loss in megapixels. Depending on the particular camera and lens combination, the resizing may have to be even more significant. For example, a DSLR with a strong AA filter and a mediocre lens may output only a fourth of the advertised MP count in terms of true detail.

After examining hundreds of Sigma SD14 images and all available DP1 samples available online, it is clear to me that the me that this Foveon sensor provides better "per pixel sharpness" than any camera I have ever owned. The quality of the detail looks as good at 100% on screen as it does resized, and that is refreshing. Rather than advertising the DP1 as a 4.6MP camera with superior per pixel sharpness, Sigma has decided to classify it based on the number of pixels in the sensor. While the latter is indeed somewhat misleading, the former would have been disastrous from a marketing standpoint. As far as I am concerned, Sigma has been as forthright as have been other camera manufacturers in declaring megapixel counts. To quote Wikipedia's entry on the Pentium 4, "a review showed that in games, it took a 5.2 GHz Prescott core to soundly beat the performance of a 64-bit Athlon FX-55 that clocked at 2.6 GHz." Thanks to AMD, most of us now know that the gigahertz specification of a computer processor gives only limited information about overall performance. Thanks to Foveon and Sigma, it is more clear than ever that the megapixel rating is a highly limited assessment of the level of detail a camera can output.

Given the available samples from the SD14, I'm satisfied that the DP1 sensor (same as the SD14) can deliver higher overall image quality than that of any other pocket camera available to date. Based on the DPReview DP1 samples, I believe that the lens will be up to the task. Therefore, despite the fact that 28mm is not the single best focal length for my overall intended use - and with the understanding that the f/4 limitation is what it is - I pre-ordered the DP1 on Amazon earlier today. Amazon initially had the DP1 available for pre-order at a price of $750. It's currently at $800. Amazon's policy is to give one the lowest price at which it is listed between the time of pre-order placement and one month after shipping. No charges are made until the camera ships. After placing my order, I was given an estimated ship date of March 31 despite availability being listed as March 25. I'd be curious to know whether anyone else who pre-ordered earlier from Amazon was given an earlier ship date, as this would suggest that they are getting a significant number of orders.

If you decide to join me in pre-ordering the DP1 and would like to tip me in the process, you can do so by using the link below to get to Amazon.

Read More......

The "megapixel war" continues. This week, both Panasonic and Casio have announced 12 megapixel sensors in their newest compact models. In general, high megapixels on a small sensor means small pixels, which translates to higher noise. While many people realize this, fewer realize that another sacrifice being made is in dynamic range. Unfortunately, none of the review sites do a great job of analyzing dynamic range performance, and few buyers consider this characteristic in choosing a compact camera. However, poor dynamic range performance forces one to choose to sacrifice either highlights or shadows when encountering a contrasty scene. The resulting dynamic range is poor, and though the tests don't show it well, the photos certainly do.

Here is an example of a quick snap with my G7, a camera into which Canon has stuffed 10 megapixels into a relatively small 1/1.8" sensor.

The colors are true and accurate, and as you can see from the full size image, the resolution is excellent. However, the highlights have been hopelessly blown. This is undoubtedly my fault, not the G7's. I could have exposed for the highlights by consulting the histogram. I could have used more negative exposure compensation and set the in-camera contrast lower knowing that the G7 has a tendency to clip highlights in such challenging conditions. However, I can tell you with complete certainty, than none of my other cameras would have clipped the highlights so severely in that image.

By comparison, here are two photos taken under similar lighting conditions with my four-year-old Leica D2. The full size versions can be viewed here and here.



Like the G7, the D2 has a small sensor. The D2 sensor is slightly larger, at 2/3"; the key difference is that it has only 5 megapixels. As a result, the pixel pitch is several times larger than that of the G7. The fact that, at the pixel level, G7 noise is not significantly different from D2 noise is a testament to the dramatic improvement of sensor technology since 2003. However, in the examples shown above, the D2 has nicely captured the dynamic range of a scene the G7 could not hope to have handled. Furthermore, both D2 examples shown here were shot at default JPEG settings. One can gain even more flexibility in dealing with dynamic range by shooting in RAW mode on the D2. Sadly, Canon has removed this option from their compact cameras, further compromising the already weak dynamic range performance.

Provided that the lens can resolve the detail, a 10MP sensor has enough pixels to capture an image from which one can crop out and discard 75% of the picture and still be left with an area that can be printed to 8x10" with good results. Most of us don't need more pixels in out pocket cameras. Poor dynamic range performance has been a weakness of digital photography since its inception, will flaw a photo even at 4x6" print sizes, and is largely ignored by makers of compact cameras as they compete for our money. Just something to consider when shopping for our next compact digital camera.

Read More......