Sigma’s SD14; D-SLR Camera With “Full-Color” Foveon X3 Pro Sensor With 14 Million Photodetectors Page 2

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All of those assessments are based on ISO 100 and 200. Images made at ISO 400 exhibit slight digital noise, reminiscent of fine grain in an ISO 400 color slide film. While shooting night scenes in Las Vegas, I found that quality at higher ISOs depended on the Capture mode used. The best results were provided by the Raw High or the JPEG High/Fine combination, without the soft, somewhat "mushy" effect produced by Super High mode. My best ISO 800 photos are quite clean with a tight grain pattern; some mottled color specks are visible in the mid-tone sky under high magnification. By ISO 1600, digital noise--especially mottling and loss of fine detail--is problematic as with most digital cameras. Of course, that ISO level is necessary only in low-light situations where there's no other way to get a sharp picture.

Images made at ISO 800 exhibit high sharpness, very good definition of fine detail, and only a bit of mottling. By ISO 1600 however, the images are "softer" and a colorful digital noise pattern is more obvious in mid-tones such as the sky. (These images were made in JPEG High/Fine capture.)

Conclusion
Because this camera requires Sigma SA-mount lenses and Sigma EF-DG series flash units, it will primarily appeal to those who have not already invested in a system of some other brand. If you fall into that category and if you want a versatile D-SLR with the latest sensor technology, ask for a full demonstration of the SD14 while comparing several models. Try its various conventional and digital features to shoot and play back a few dozen frames. Within 10 minutes, you should know whether this camera will meet your shooting needs. Add some of the fine Sigma lenses and a flash unit, and you'll be well on your way to serious image-making.

Both JPEG High/Fine and Raw High capture can produce fine image quality, although the raw file does exhibit greater definition of fine detail and total freedom from JPEG artifacts. But the primary benefit of raw capture is the adjustability of numerous image parameters--before actual processing--in the Sigma Photo Pro 3.0 or other converter software. (Image made at ISO 100, using a Heliopan Super Multi-Coated polarizer.)

Resolution Issues
The SD14 is marketed as a 14.1-megapixel model and that has led to debates. Sigma Photo's technical White Paper indicates that this is "a 14-megapixel--2652x1768x3 layers--Digital SLR...that provides three pixels at each location...as opposed to separately located." That assessment is in line with Japan's Camera & Imaging Products Association guidelines but some technical analysts disagree. While there may be 14 million "photodiodes" or "photodetectors," the sensor includes only 4.6 million effective "pixels," they claim.

An image file made with Raw High or JPEG High capture is not very large (13.3MB), but the overall quality can be superb, thanks to the unique technology employed by the Foveon sensor. This technically excellent raw photo, for example, made for a richly detailed 11x16.5" print suitable for framing. (Image made at ISO 100 without a polarizer, converted with Sigma's Photo Pro 3.0, and optimized for printing with Photoshop CS3.)

This debate is not likely to end until international standard setting organizations, such as ISO, publish their own definitions. On the other hand, many experts agree that pixel count is only one measure of actual resolution and overall image quality. That certainly makes sense and my evaluations do consider general image quality in large prints.

Basic Pixel Count: Looking at this issue from a conventional perspective produces the following data: Open an image made in the High size JPEG Capture mode in Photoshop or other software and it consists of 2640x1760 pixels. The file size, in megabytes, is approximately 13.3MB. (A raw file, after conversion to 8-bit color TIFF with the Sigma Photo Pro 3.0 software, is the same size.) That's not very large by familiar standards, but the excellent image quality allowed me to make beautiful 11x16.5" inkjet prints at 240dpi, after using Bicubic Smoother interpolation to increase the image file size in Photoshop.

Additional Pixels: The SD14 provides another JPEG Size option: Super High (not available in raw capture). When that's selected, you'll get an image with 4608x3072 pixels, achieved with in camera interpolation, a sophisticated method that adds pixels by copying existing pixels. When the Super High JPEG is opened in a computer (no longer compressed) it's approximately 40.5MB in size. While the camera's interpolation process causes some "softening" and a loss of ultra-fine detail, overall quality is still very good, particularly in images made at ISO 100-400. After some tweaking with Photoshop's Smart Sharpen utility, my technically best Super High/Fine JPEGs made for excellent 13x19" inkjet prints at 240dpi.

Of course, it's easy to "res-up" a 13.3MB image to a 40MB file size in a computer. However, I found that in camera interpolation in Super High capture produced better results than Photoshop's Bicubic Smoother option. Because the camera enlarged the image file before actual processing, it maintained higher sharpness and definition of fine detail.

There's another method that can be used when an oversized image file is required: shoot in Raw High (2640x1769) mode and enlarge the file in raw converter software. The Sigma Photo Pro 3.0 program does provide a single option for that purpose, labeled as "Double." When selected, Photo Pro 3.0 generates a 50MB TIFF file instead of the typical 13.3MB file. Problem is, that aggressive interpolation process causes a significant deterioration in image quality, so this option is not really useful for large prints.

Better results are possible with the interpolation feature available with Adobe Camera Raw in Photoshop CS2 or CS3. When starting with an X3F format raw data file, the Adobe program's "17.5Mp" option produced a 50MB TIFF file of decent quality. However, the less ambitious "11.2Mp" option generates a 32MB file of superior quality that made for excellent 13x19" prints. While the Sigma Photo Pro 3.0 software is ideal for basic conversion of X3F format files, Adobe Camera Raw does provide better results in this respect.

The Bottom Line
While I have no scientific method of measuring pure resolution, the SD14 produced superb quality in JPEG High/Fine capture, equivalent to what I would expect from an 8-megapixel D-SLR. That assessment is somewhat subjective, based on extensive experience with other cameras and a close visual examination of large inkjet prints. In JPEG Super High/Fine mode--especially at ISO 100 and 200--the overall image quality is similar to what I expect from a 10-megapixel D-SLR. At high ISO levels however, image quality does suffer in Super High JPEG capture (as discussed elsewhere in this report), making the other options preferable in low-light photography.

In order to evaluate the image quality available in JPEG High/Fine vs. Super High/Fine capture, I often shot the same scene with both options and made large prints for comparison purposes as discussed in the text. A much larger Super High file exhibits lower sharpness, but that's easy to correct in post-processing and the extra resolution data is useful when making 13x19" inkjet prints. (Both images made at ISO 100, using a Heliopan Super Multi-Coated polarizer.)

For more information, contact Sigma Corporation of America, 15 Fleetwood Ct., Ronkonkoma, NY 11779; (800) 896-6858; www.sigma-photo.com.

A long-time "Shutterbug" contributor, stock photographer Peter K. Burian (www.peterkburian.com) is the author of several books, including "Mastering Digital Photography and Imaging" as well as "Magic Lantern Guides" to the Sony A100 and Pentax K10D. He is also a digital photography course instructor with BetterPhoto.com.

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