Articles, Insights, and Tutorials
Kodak Professional's new DCS 620x digital camera, pushing the boundaries of available-light shooting.
This new version of the DCS 620 digital camera performs at up to ISO 6400 and delivers improved image quality with its innovative high performance 2-megapixel CCD, utilizing a Cyan-Magenta-Yellow (CMY) Bayer pattern color filter array.
ISO 400 Sample
Daylight, Nikkor f2.8 80-200mm f2.8 zoom lens, Auto White Balance, Aperture Priority, Matrix Metering, Aperture f8, Shutter 1/2500th, Anti-Aliasing filter installed, Acquire Module Version 18.104.22.168.
Click on the preview at left for a 1200 x 800 pixel, 297 KB full screen view.
ISO 1600 Sample
Available Light, Nikkor f2.8 400mm lens, Aperture f2.8, Shutter 1/1000th, Anti-Aliasing filter installed, Acquire Module Version 22.214.171.124.
Click on the preview at left for a 1200 x 984 pixel, 296 KB full screen view *.
*Photo courtesy of Dallas area pro photographer (and good friend) Moses Olmos.
ISO 3200 Sample
Available Light, Nikkor f2.8 28mm lens, Auto White Balance, Programmed Automatic Exposure, Matrix Metering, Aperture f2.8, Shutter 1/200th, Anti-Aliasing filter installed, Acquire Module Version 126.96.36.199.
Click on the preview at left for a 1200 x 800 pixel, 384 KB full screen view.
ISO 6400 Sample
Available Light, Nikkor f2.8 28mm lens, Auto White Balance, Programmed Automatic Exposure, Matrix Metering, Aperture f5.6, Shutter 1/125th, Anti-Aliasing filter installed, Acquire Module Version 188.8.131.52.
Click on the preview at left for a 1200 x 800 pixel, 408 KB full screen view.
The Technology Inside the 620x
By Stephen A. Noble, Advanced Development Manager
Digital Capture Engineering, Kodak Professional.
The new Kodak Professional DCS 620x digital camera, a variant of the DCS 620 (which remains available), is notable for its ISO range of from 400 to 6400 (calibrated from ISO 400-4000), and its impressive image quality. Key to these features are a new 2-megapixel indium tin oxide CCD (charge couple device), new color filter array (CFA) pattern, and new low-noise electronics. The camera is ideal for fast-action, low-light and changing lighting conditions.
Kodak's high-performance 2-megapixel CCD in the DCS 620x utilizes a Cyan-Magenta-Yellow (CMY) Bayer pattern color filter array. This new color pattern (shown below) looks very similar to the RGB Bayer pattern used in the DCS 620.
In fact, Dr. Bayer, a Kodak scientist who invented the Bayer pattern approximately 20 years ago, suggested in his original patent that either RGB or CMY colors could be employed. Until now, Kodak DCS cameras have employed the RGB pattern because of issues with color fidelity and CCD manufacturing. However, CMY deployment is now possible, thanks to groundbreaking advancements in CCD design with indium tin oxide (ITO) materials and newly developed CFA manufacturing techniques.
The major advantage of CMY CFA colors is sensitivity, or speed. In photographic terms, speed is equivalent to ISO. The CMY CFA has two attributes that increase effective speed:
· Less unwanted dye absorption
· Increased color signal and signal-to-noise ratio
The reduced dye absorption behavior of a CMY CFA is easy to explain. In the RGB CFA system, each color is "built" from a combination of two of three available dye layers - cyan (C), magenta (M) or yellow (Y). For example, the green layer is "built" by combining one layer of yellow and one layer of cyan.
Therefore, the RGBs are built with the following formulas:
Red = Y + M
Green = Y + C
Blue = M + C
Even though a single color - say, Y - is supposed to pass yellow color and absorb all others; it has a tendency to absorb yellow as well. This is called unwanted absorption. Since both colors that make up any particular primary RGB color have unwanted absorption, this further reduces the amount of light that passes through to the CCD. In the CMY system, there is only one dye color for each primary color. So this system has less unwanted absorption, effectively passing more primary light to the CCD.
The discussion around increased signal is a bit more complicated. First, let's examine a few basics on how CCD's work.1 The photoactive area of a CCD pixel is the region that converts light to electrical charge. This electrical charge is proportional to the amount of light striking the pixel. To create a CCD readout, the electrical charge is converted into a proportional voltage, and the A/D (analog to digital) converter subsequently samples this voltage.
When the camera shutter "takes" the picture, each CCD pixel is presented with an amount of light that originated in the scene being photographed. Also, each color in the scene is made up of different amounts of energy at particular wavelengths of light. All the wavelengths of light striking the pixel are "integrated" (averaged together) to form the signal at each pixel.
If a pixel has a color dye placed above it, as in the case of a color CCD, then that pixel will respond more to that particular color. Therefore, the green pixels in a RGB Bayer pattern CCD respond more to green scene content, but the total green signal is developed by integrating all the energies in the entire 400-700nm wavelength band.
In the case of green, that means more energy is allowed to pass through to the CCD in the green area of the spectrum and less in others. Refer to the CCD response vs. wavelength chart below.
This chart shows both an RGB and a CMY CCD response. The chart was made by combining data from the two different CCD systems. Note the green line, which is the green response of the RGB system. Compare it to the yellow line, which is the yellow response of the CMY system. You should notice two attributes.
First, the yellow curve is much larger in overall amplitude (approximately 37% yellow vs. 20% green). This occurs because of the reduction in unwanted absorption mentioned earlier. Second, you should notice that the area "under the curve" for the yellow is much larger than the green signal. Notice that yellow starts rising at about 500nm and stops responding at 700nm, but the green signal, while it also starts at 500nm, ends at around 600nm.
If you were to shine a light source that has constant energy at all wavelengths onto the CCD, the yellow signal would be about twice as large as the green signal. This occurs because the yellow signal integrates more light compared to the green signal. Since in either case the noise in the underlying CCD is constant, we also have larger signal-to-noise ratio (SNR) in the CMY system. This larger signal provides higher effective ISO, and the increased SNR provides for more ISO range.
The increased ISO range was used to maximum advantage in the DCS 620x system. Note that the DCS 620 has an ISO range of 8x - 200 to 1600 - while the DCS 620x has a range of 16x - 400 to 6400. The larger signal of the CMY system provides the increased base ISO of 400, and the greater SNR provides for the increased ISO range.
As mentioned earlier, the DCS 620x also incorporates new lower-noise analog electronics compared to the DCS 620. This further increases SNR, and enhances the ISO range of the CMY system. While this is very difficult to see at the base ISO of 400, the image quality improvement at ISO 6400 is quite noticeable.
It is precisely that image quality at very high ISO settings that will appeal to photographers who shoot digital images in changing and dim-lighting conditions. For them, the most important thing is to "get the shot," but not at the cost of poor image quality. With its unique combination of technology, the DCS 620x provides the perfect solution.
Digital photographers who shoot in changing and low-light situations can now reap the benefits of extremely high ISO settings with the new Kodak Professional DCS 620x digital camera. A version of the workhorse DCS 620 model, this new camera features ISO settings ranging from 400 to 6400. The new model also provides improved image quality, which enables photographers to push the boundaries of digital imaging to even greater limits.
"Photojournalists and other professionals have already come to rely heavily on our DCS 620 camera," said Peter Jameson, Director, Digital Capture, Kodak Professional. "This enhanced version of the camera will make it even more invaluable for photographers who are challenged to shoot fast action or in low-light conditions, including sports/action, medical and scientific imaging, government, military and law enforcement. The DCS 620x camera offers improved flexibility and expandability along with increased quality - a truly winning equation."
Key to the DCS 620x digital camera are a new CCD (charge couple device), color filter array (CFA) pattern, and low-noise electronics. The new CFA on Kodak's 2-megapixel ITO (indium tin oxide) CCD provides enhanced spectral response, producing high picture quality at extremely high ISO ranges.
Like the DCS 620 camera, the DCS 620x is built on the Nikon F5 platform and retains all the durability, functionality and lens compatibility of that single-lens-reflex camera.
The Kodak Professional DCS 620x camera provides a host of features that ensure superior image quality and higher color saturation. In addition to a new software noise reduction filter, the DCS 620x offers Kodak's "Picture Protection" - a range of features that includes post-shot exposure compensation, white balance corrections and file recovery.
Plus, photographers can customize the DCS 620x with such options as removable anti-aliasing and IR blocking filters, IPTC captioning, white balance uploading, direct cellular phone transmission, and a wide choice of storage options.
- 2-megapixel (1736 x 1160) 13um, ITO, CCD sensor.
- Flexible ISO of 400 - 6400 (calibrated from ISO 400-4000).
- Serial port for GPS receivers and direct cellular telephone connectivity.
- Burst rate of 3.5 frames per second, and a sustained burst depth of 12 images.
- Patented on-board histogram lets photographers verify exposure accuracy on the spot.
- Cast magnesium alloy body ensures high durability, while its light weight makes it ideal for field use.
- Calibrated color response and the TTL auto color balance option ensure that the camera adjusts image color to match the light source.
- 36-bit color (12 bits per channel) for capturing color and detail in shadows and highlights.
- Intervalometer to enable automated capture over timed intervals for remote applications.
- Open Application Programmer Interface (API) lets third-party developers write their own custom software applications.
- Color liquid crystal display (LCD) provides instant review of images.
- IEEE 1394 interface provides fast and reliable transfer of images.
- Voice annotation provides audio notebook to document specific shots.
- Dual PC card storage interface offers storage flexibility.
- Delivers 6MB finished files in 24 bit RGB.
- Onboard JPEG compression with three levels of resolution.
- Removable batteries for easy transport and recharge.
- New NiMH batteries for extended battery life.
- Improved version 5.9.1 Adobe PhotoShop Plug in / TWAIN acquire software tools.
The new camera follows closely on the introduction of the latest DCS series firmware and software upgrades that include enabling dual memory card slots, GPS data recording and laptop-free image transmission via cellular phones.
How does the DCS 620x differ from the DCS 620 digital camera?
The DCS 620x has all the functionality of the DCS 620, but also incorporates a new CCD (charge couple device), color filter array (CFA) pattern, and low-noise electronics. As a result, the DCS 620x features ISO settings ranging from 400 to 6400. The new CFA on Kodak's 2-megapixel indium tin oxide CCD delivers enhanced spectral response for high-quality images at extremely high ISO ranges and with greater color saturation.
Who will benefit most from the DCS 620x?
Photojournalists, especially those shooting sports and action; photographers in the medical, scientific imaging, government, military and law enforcement fields; and others who have to capture digital images in low-light or changing lighting conditions.
What other features does the DCS 620x offer?
The DCS 620x has a range of features that ensure superior image quality and higher color saturation. In addition to a new software noise reduction filter, the DCS 620x offers "Picture Protection" - a menu of features that includes post-shot exposure compensation, white balance corrections and file recovery. Photographers can customize the camera with such options as removable anti-aliasing and IR blocking filters, IPTC captioning, white balance uploading, direct cellular phone transmission, and a wide choice of storage options.
Does the new camera replace the DCS 620?
No, there is a market for both. The DCS 620, as well as the DCS 520, remain in Kodak's award-winning line of professional digital cameras.
Given the advances in the DCS 620x, why would anyone want to buy a DCS 620?
The DCS 620 is an excellent camera in its own right, offering high performance with an ISO range of 200-1600. For photographers who don't need extended low-light capabilities, the DCS 620 provides all the features of the DCS 620x at a reduced price.
You say the DCS 620x has an ISO of up to 6400, but is calibrated only to ISO 4000. What does that mean exactly?
The DCS 620x camera is optimized, calibrated and tested for operation from ISO 400 to ISO 4000. Comments from early users suggested that, for low-light photography at very high ISO, the trade-off of quality for speed is acceptable. So the camera can be operated at up to ISO 6400, but image quality and color may not be suitable for some applications.
Why is the lowest ISO setting 400 when other cameras offer lower settings?
The DCS 620x is designed specifically for photographers who shoot - especially action - in low light, and a 400 ISO is the minimum setting for that situation.