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Home , 35 mm format, Four Thirds System, Image quality, Image sensor

Resolution vs. Size, Optical Format 13 defined as the ratio of the 12 4/3-type Imager from the sensor for a 4/3-type Image Four Thirds 2/3 inch Imager 11 System 1/2 inch Imager given illumination condition 10 and time relative to in Digital Still 4/3-type 9 the measured pro- duced from the sensor’s dark 8 Applications 4/3 current and read-out circuit- 7 Resolving ry. While many photogra- Consumer Power KAF-5101CE 6 Market 5M pixel FF-CCD phers seem satisfied with the

Resolution (M ) 5 of today’s dig- Silicon Image Sensors - In the Digital Still Camera Marketplace 2/3" 4 ital , Kodak’s 4/3- 1/2" ilicon image sensors have been paramount seeking higher performance and versatility , as well 3 Increasing type , based on in establishing the wide market acceptance as improved value relative to traditional 35-mm dig- advanced full-frame CCD 2 Sof digital still . Kodak’s Image ital SLR cameras and . 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 technology, delivers notice- Sensor Solutions division offers a broad array Pixel Size (µm) ably better and estab- of image sensors (see Fig. 1) for a variety of Figure 6: Image sensor resolution vs. pixel size for various optical formats lishes a higher standard for digital applications. Now a next- digital pictorial quality for generation format is being introduced that ding charge capacity, the cam- professional photographers. will dramatically alter the market landscape. eras achieve 11 to 12 bits of dynamic range, equiv- Referred to as the “4/3-type” format, this 4:3 alent to the best digital SLR cameras in the profes- Kodak KAF-5101CE – A 5 Mega-pixel, format with a 22-mm photo- sional market today. 4/3-type Image Sensor graphic diagonal is targeted for the profes- The Kodak KAF-5101CE is a full-frame CCD sional market segment. It will Photo-Sensitivity (charge-coupled-device) that has been specifically enable a revolutionary new generation of Many of today’s digital cameras are deficient in designed for Four Thirds System digital SLR cameras. high-quality, highly portable digital still cam- photo-sensitivity (effective ISO), performing relative- The KAF-5101CE incorporates 6.8-µm pixels with an eras for professional and advanced amateur ly poorly when capturing action photography in integral pigment and micro-lenses photographers. Figure 1: Kodak’s image sensors for performance poorly illuminated environments. To achieve a high- for superb color rendition and high photo-sensitivity. imaging applications. er effective ISO, the digital gain in these cameras is It delivers high image quality with low noise at frame Digital from the ground up, the Four Thirds System often increased and, with this, a commensurate rates of up to four (4) frames per second and an ISO unburdens camera makers from compatibility with level of noise is introduced into the images. Many range from ISO 100 to ISO 800. The KAF-5101CE is the traditional camera and lens formats from film- Common Optical Formats amateur photographers have been disappointed available with a companion timing generator chip based imaging, allowing them to optimize all the Digital still camera formats vary widely across the with the performance of their consumer digital that is specifically designed to optimize its perform- elements of digital camera design to achieve excel- different market segments. At the high end of the cameras in dimly lit gymnasiums, auditoriums or ance for digital still cameras. Together, these chips lent quality and high functionality with a more com- professional market segment, for example, digital other venues where lighting is insufficient or where augment Kodak’s broad line of image sensor solu- pact camera system. The power of the 4/3-type cameras based on so-called ‘645’ motion is involved such as in sporting events. tions for performance imaging applications. imager comes from the synergies of its optimally focal plane use image sensors that are larger than However, with a Four Thirds System digital camera, matched Four Thirds System cameras and lenses. the 35-mm optical format (See Fig. 2); while 35- the effective ISO range is now 100 to 800 and can The Bottom Line Relative to today’s consumer cameras, the sensors mm and APS format imager sensors serve the pro- produce quality images in this diffi- Digital from the ground up, the Four Thirds System are large, high resolution devices with excellent fessional and advanced amateur markets, which uti- cult photographic space. It’s funda- creates a new category of digital still cameras with dynamic range, photo-sensitivity and signal-to-noise lize 35-mm digital SLR cameras. Consumer point mental physics: a larger imaging its combination of professional qual- performance. And, relative to the professional 35- and shoot cameras, in contrast, use much smaller area, combined with larger pixels ity and versatility at affordable mm format cameras, the new Four Thirds System silicon sensors such as 2/3 inch, 1/2 inch, 1/3 inch and new lenses specifically prices. Kodak offers a 5 mega-pixel digital SLR (single lens reflex) cameras offer a set of format and even smaller. Camera makers must designed for silicon sensors, 4/3-type image sensor solution that interchangeable lenses that will be inherently lighter choose an imager format based on the price target results in improved image quality lies at the heart of this exciting new weight, more compact and highly portable while for their camera, since the imager cost increases expected in professional digital digital SLR camera format for profes- providing professional quality images. with its size. While the precise geometries vary from SLR cameras. sionals and advanced amateurs. chip maker to chip maker, the most common for- The new 4/3-type image sensor offers professional mats are categorized in the table on the following Signal to Noise Ratio Figure 7: Kodak KAF-5101CE, 5 Mega- image quality with a smaller optical format, creating page. The 4/3-type image sensor, with new lenses pixel Full-Frame Color CCD Image Sensor A classical measure of image quality in digital pho- an exciting advantage for professional and designed to match the optical format, provides pho- tography is the signal-to-noise ratio of the image Image Sensor Solutions • (585) 722-4385 advanced amateur photographers. This new cate- tographers with the digital still camera performance sensor and camera system. This factor can be www.kodak.com/go/imagers gory of digital SLR cameras will appeal to those expected by professionals and advanced amateurs. [email protected] 35-mm Format Frame Imager Aspect Width Height Diagonal example, introduces an undesirable Format Ratio H (mm) V (mm) (mm) magnification error, which effectively reduces the APS Format Imager Resulting Image 1/4” 4:3 3.2 2.4 4 photographic for a given focal length 1/3” 4:3 4.8 3.6 6 (See Fig. 4). This creates a barrier to achieving wide 1/2” 4:3 6.4 4.8 8 angle photography with short focal length lenses 2/3” 4:3 8.8 6.6 11 that are designed for a full 35-mm format frame. 1” 4:3 12.8 9.6 16 While full 35-mm format image sensors can be used 1 4/3-type 4:3 17.8 13.4 22.3 to alleviate this problem, their higher cost results in APS 2 3:2 25.1 16.7 30.1 a camera price that may be prohibitive for advanced 35 mm 3:2 36.0 24.0 43.3 amateurs and even many professionals. Since 4/3- Figure 4: Photographic effect of an APS format imager used with 35-mm format camera with an f/3.0, 36x36 1:1 36.0 36.0 51.9 type image sensors and lenses are precisely 38-mm effective focal length lens 645 4:3 56.0 41.5 69.7 matched, there’s no magnification error introduced. The problem is confounded because the incident ISO, dynamic range and signal-to-noise perform- As such, no matter what type of lens is being used- angle is a strong function of the focal length and f- ance. It is a high resolution format from the first Footnotes: -wide angle, variable zoom or telephoto--the full 1. 4/3-type imager as described by Kodak KAF-5101CE image stop of traditional 35-mm lenses and, as such, generation on, with significant “head room” for sensor field of view presented to the user is usable photo- peripheral fading is dependent on each lens being going to much higher pixel counts and well beyond 2. Common ‘APS’ digital format: 23.7 mm (H) x 15.6 mm (V), graphic area. This provides professional and used. While large incident angles are not a problem the practical limitations of smaller format sensors. 28.4 mm diagonal advanced amateur photographers with wide angle for film-based photography (because silver-halide Kodak’s first 4/3-type image sensor, the KAF- photographic capability that is only commercially photo-sensitivity is relatively independent of inci- 5101CE, has 5-million 6.8 µm x 6.8 µm pixels and The 4/3-type Optical Format available in more expensive camera systems. dent angle), it is highly desirable that the inci- renders exceptional detail while maintaining high The new 4/3-type format defines an optimal sensor dent angles be more normal (perpendicular) for sili- image quality; and 8 million, 10 million or even 12 size for its target market, Four Thirds System digital con image sensors, whose architec- million pixels are not unrealistic in the years to come SLR cameras for the professional segment. It’s more tures prefer normal incidence. for the 4/3-type format (see Fig. 6). compact than the APS format, yet has four times the active area of the 2/3 inch format, effectively quad- Resolution and Pixel Size Dynamic Range rupling the photographic area available for capturing Despite the on-going “pixel wars” among some Also referred to as “bit depth” or “contrast range,” an image over the best sensors available in the con- digital camera makers in the consumer market, the dynamic range of an image sensor can be sumer market segment today (See Fig. 3 for relative packing more and more pixels into the same size 1/2 thought of in terms of a camera’s ability to render sizes). Moreover, the characteristics of 4/3-type inch format or 2/3 inch format sensor ultimately the gradation of shades of gray in the highlights image sensors have been designed to work optimal- leads to diminishing returns. As one adds pixels, the and shadows of a scene. The effective dynamic ly with Four Thirds System lenses, and these new constraint of the optical format limits the pixel size, range can be examined in the details of the bright- lenses are specifically being designed to operate with reducing the photo-sensitive area and charge est highlights in an image and in the darkest shad- silicon sensors, not with traditional silver halide film. capacity of these shrinking pixels. ows of an image. Some of the today’s best studio- grade camera systems claim 14 bits of dynamic Wide Angle Photography The 4/3-type image sensor alleviates this conflict by range (some scanning backs even claim 16 bits) with Digital SLR Cameras Figure 3: Comparison of 4/3-type, 2/3 inch and 1/2 inch defining an active area four times larger than 2/3 while most of today’s consumer cameras deliver 8 to In commercially available 35-mm SLR digital cam- optical formats inch sensors, which dramatically improves effective 10 bits. Due to the larger pixel size and correspon- eras today, the image sensor selected for the cam- era is often considerably smaller in area than the Matching Image Sensor and size of the 35-mm film for which the lens was orig- Lenses In Digital Camera Design inally designed. This trade-off is necessary in order The 4/3-type image sensor and Four Thirds System to save cost, but it also causes some serious com- lenses have been co-optimized without the con- promises in performance. The size difference, for straints of traditional 35-mm film lenses. Based on an understanding of how silicon sensors operate, these new lenses are more tele-centric, introducing light rays to the image sensor surface at incident

1/3” angles that are more perpendicular. This reduces 1/2” 1/4” 36mm x 36 mm the effect of peripheral fading observed with tradi- 1” 4/3-type APS (3:2) 35 mm 645 2/3” tional 35-mm film lenses used in digital SLRs today, Figure 2: Common image sensor formats used in digital where sensitivity roll-off near the edges is consider- Figure 5: Incident light rays for a non-telecentric film camera objective compared to a nearly telecentric digital camera objective. Since telecentric designs typically require more elements the smaller Four Thirds System lens elements result in still cameras able due to large incident angles (see Fig. 5). more compact, cost effective lenses as compared to similar designs in the 35-mm format.