Machine Design

Forgot film? No problem for digital cameras

The world of still-photography is experiencing a revolution, the likes of which we haven't seen since the 35-mm film format became standard for popular consumer use around the 1950s.

The most recent breakthrough in digital cameras comes from Olympus America Inc., Melville, N.Y. It announced the C-211 Zoom, developed jointly with Polaroid Corp., Cambridge, Mass. Available in October, it features all the normal digital qualities expected of a high-end camera plus an instant, hardcopy print. The prints are made on silver-halide film to verify the stored image and helps tracking and archiving images without needing a computer. The 2.1 megapixel camera with 1,600 1,200 resolution takes still pictures as well as movies in a viewing mode using QuickTime computer software.

The Coolpix 990, is a 3.34-megapixel, top-ofthe-line digital camera from Nikon, Stamford, Conn., priced at just under $1,000 and uses a 16-Mbyte CompactFlash card. The card plugs into the USB port of a PC or Macintosh computer through an adapter for downloading large pictures. The camera can capture from one to 322 images on a single card, depending on the resolution and compression ratio.

Vivitar's new ViviCam 3500 digital camera features two grades of resolution; 1,360 1,024 pixels for fine and normal images, and 640 480 pixels for storing more images. It uses CompactFlash memory cards with capacity to 48 Mbytes, and stores 10, 20, or 40 images depending on resolution. Connections to the computer are through USB or RS-232 ports.

The amount of light reaching each photosite through the camera lens is represented by a vertical bar whose height is proportional to the charge intensity.

NuCORE Technologies Inc. claims this chip set can deliver a three-CCD sensor color quality image from a single CCD or CMOS camera. The two chips are composed of an NDX-1250TM analog front end and the SiP-1250TM smart image processor that can handle 50 megapixels/sec at 12-bit resolution. Both chips use special algorithms to deliver high-quality, high-resolution images with wide dynamic range by amplifying the R, G, and B signals separately, although the three signal processing chains merge into one.

The NuCORE chip set divides the digital camera processing function into two areas. The front end is an analog chip, and the second chip is the digital portion. Both chips process portions of the image. The high-speed imaging capability lets the chips work in high-end cameras that can provide 4-megapixel digital still pictures and 1.3 million pixel video at 30 frames/sec with 12-bit accuracy.

Sony Electronics recently developed a 3.3-megapixel digital camera called the Cyber-shot containing Carl Zeiss lenses and optical viewfinder. The three models in the family cost 500, 600, and $800, and all have 12-bit A/D conversion and 33 optical and six digital zoom lenses. Resolution for the two lower-cost models are 1.6 and 2.1 megapixels. Sony's Memory Stick image storage media comes in 8 to 64 Mbyte sizes, with a 256 Mbyte unit in development.

The world of still-photography is experiencing a revolution, the likes of which we haven't seen since the 35-mm film format became standard for popular consumer use around the 1950s. Who could have dreamed that in less than five years, electronic digital photography would move from a curiosity to an enormous industry supplying digital cameras and software tools to professionals and hobbyists at affordable prices? And experts predict that digital cameras will continue to get even better and cheaper.

During the past two years, the one factor that seemed to be a critical issue in deciding the quality or resolution of a digital picture compared to 35-mm film — the number of picture elements or pixels — has grown from around 1 to about 4 million. Sensitivities of the solid-state devices that capture the images have increased, allowing more photosensitive sites for generating the pixels on a silicon chip and provide resolution as fine as film. (The number of photosites or photo-diodes don't necessarily equal the number of pixels.) The average "good-quality" camera today is likely to offer 2 million pixels — two megapixels — or more.

Megapixel is a term that comes from the product of the number of rows and columns in an array. One megapixel requires an array of at least 1,000 X 1,000 pixels, or a similar aspect ratio. In general, the rule of thumb is, the more pixels a camera can handle, the larger a print that can be made from the file and remain sharp. However, not all the photodiodes are used to capture the image. Some help process the image in other ways, such as color balancing.

In any case, most cameras registering 1.3 million pixels go for less than $300 and can produce acceptable 4 6 and 5 7-in. prints. However, if you expect at least 300-dpi (dots/in.) resolution at 5 7 in., you will need roughly 1,500 2,100 pixels or a 3.15-megapixel camera. By comparison, dropping down to 200 dpi requires only about 1.4 megapixels. Although some purists might argue that digital quality still falls short of film, no one can argue about the convenience digital photography offers in the ability to use computers to process and touch up the images easier, faster, and cheaper than can be done in the traditional chemical darkroom.

What's more, digital cameras don't have to sacrifice any of the features that film cameras currently furnish. In fact, on average, they offer more. For example, many digital cameras provide optical zoom and a digital feature called magnification that film cameras can't match. Optical zoom in digital cameras is the same as in conventional cameras, but digital zoom frames a smaller image on the CCD and interpolates the image to make it appear to zoom into the original image. And for panoramic shots, cameras like the Olympus D460 ZOOM can "stitch" multiple shots together (horizontally or vertically) to make one large seamless panoramic view. In addition, some models have changeable lenses for different needs, built-in flash, time-date stamps, and automatic settings for aperture (f-stops) and shutter speeds.

Some more widely used features include a color LCD viewfinder, that either accompanies the optical viewfinder or replaces it. Another is a monochrome LCD that can be seen at any angle for displaying the program menu and modes. Typical display modes include one frame, slide-show, close-up, and index display. Other cameras could have black-and-white mode, and provide sepia tones, black boards/white boards, and special effects.

In addition, one camera comes with a burst mode that snaps off six to 10 images automatically at 0.5-sec intervals. Other cameras can handle more or less the same number of images in roughly the same time. The Olympus C-2020, for example, includes a Quick-time movie mode used on computers. It shoots 15 frames/sec up to 60 sec at 160 X 120 resolution, and 15 sec at a higher 320 X 240 resolution.

If all that were not enough, some cameras offer fully automatic white balance (for compensating the various types of light sources), automatic focus, and automatic flash which adjusts for back-lighted subjects. Moreover, the intelligent flash system selects red-eye reduction, fill-flash, or flash-off modes. Many digital cameras can focus on a subject as close as four inches with the original lens, and some high-level cameras can get down to 0.8 in.

On the downside, however, batteries take much more of a beating in digital cameras than in most other types. Mark Horning, photographic expert at DODD Camera and Imaging, Cleveland, has used them all. He warns to take plenty of batteries along on your photo sessions, whether they be rechargeable types or not. "You will be surprised how often you will need to change the batteries, particularly when you become absorbed in your shoot," says Mark. Among the most often used types are rechargeable lithium, alkaline, rechargeable nickel cadmium (NiCd), and nickel-metal hydride (NiMH).

Images are captured on charge-coupled devices (CCDs) or CMOS sensor chips behind the lens and transferred to a memory card or floppy disk plugged into the camera. (See side-bar Shedding some light on the subject.) But CCDs and CMOS sensors by themselves can only sense gray tones ranging from white to black, or varying brightness. Color is produced using red, green, and blue (R, G, and B) filters by one of three techniques:

  • Take three separate exposures, each with a different color filter and postprocess the combination,
  • Use three separate sensors and image channels with their own color filter and then combine downstream,
  • Place R, G, and B filters over a group of photosites in a particular pattern (specific pattern determined by sensor maker) to capture only one color at a site and "superimpose" them at the output.

Images captured by the CCD are typically stored on a memory card or a floppy disk, or they may be transferred directly to a computer with a special serial interface cable. Memory cards replace the film and have several qualities that the film can't match. For instance, memory cards can transfer images directly to a personal computer or another memory card. These images can be manipulated in the computer to provide a myriad of effects. It can superimpose images, alter the size, shape, or color in any manner to give some startling presentations, or it can touch up and artistically restore prints, much the way it's done now in professional darkrooms.

Memory cards come in many sizes, measured by the number of megabytes they store. Most cameras come with 8 or 16-Mbyte cards, but these cards are now available up to a whopping 1 Gbyte. Claims for capacity of the 8-Mbyte cards range from 8 to 15 pictures for one camera maker to 122 images for another, depending on resolution. Typically, fewer images can be stored as the resolution increases. Cards usually come in capacities of 2, 4, 8, 16, 32, 64, and 128 Mbytes, but for a hefty price, they also come in 224, 448, 512, 640, and 768 Mbytes.

Three types of cards are currently offered, called SmartMedia (Toshiba), Memory Stick (Sony), and Compact-Flash (Panasonic and others). Except for the Memory Stick, they are based on the so-called PCMCIA cards often used in laptop computers, also dubbed Type II memory cards. These cards normally download through a cardreader connected to the computer's serial, parallel, or USB port.

A floppy disk drive adapter is also available that lets you download a SmartMedia card directly in the drive. Some cameras use the floppy disks themselves as memory devices, but they have relatively low capacity and are slow. Just three years ago, they were widely used, and although floppies are the least-expensive media, the newer solid-state memory cards are quickly displacing them.

When saving large files, most cameras provide several formats and levels of compression to optimize the storage media. That is, fewer images of higher resolution can fit on a given size memory device. For example, formats such as JPEG (Joint Photographic Experts Group), compress the data at a ratio of 10:1 or less which surprisingly does not compromise the image. On the other hand, TIFF (Tagged Image File Format) is used to save images in an uncompressed format for the highest resolution images. Some cameras can do both during one shooting session. However, other cameras use a proprietary compression scheme and may not be friendly with software other than that supplied with the camera. This limits your software choices and your ability to be more creative in the "desktop darkroom."


CCD sensors contain an array of photodiodes, also called photosites, that sit behind the lens where the film normally resides. These sites pick up the image and convert the varying light intensity across its surface to electrical charges. The magnitude of the electrical charge at each site is proportional to the amount of light impinging on it and is assigned a number value to be used by the processor for reproducing the final image.

Silicon chips take the place of photographic film to capture the image. A chip may measure less than an inch on a side, and contain an array of individual photodiodes that, at the microscopic level, resemble the familiar dots on a color picture tube. Each square, flat-topped diode is called a photosite, and converts the photons of light that fall on them into a corresponding number of electrons that are proportional to the brightness level at that point of the image. The brighter the image at a site, the more electrons that are generated. The array contains hundreds of sites in rows and columns, and the product of these rows and columns equal the total number of sites which, in turn, are proportional to the number of pixels. The pixel count varies from 1 to 4 million, and in the aggregate, are called megapixels.

The electronic charges at each photodiode are shuffled off the array one row at a time, sent to a register, and then stored in a flash-memory card. Each row of charges is continuously tracked through the capture, processing, and outputting steps to ensure that the original image is faithfully reproduced for the presentation step, that is, when you finally view your picture.

Depending on the particular camera maker, processing includes the method of reproducing color images, correcting background artifacts, ensuring sharpness, color correction, and compressing the image without losing detail to conserve storage space.

Low-end color cameras might get away with using only one CCD and image-processing channel, but they can't deliver the resolution and color correctness that cameras with multiple channels can. The output signal from each photosite in a single CCD is compared with its neighbor, and through an algorithm in a micro-processor, it determines the brightness, contrast, and color properties of the image. On the other hand, most medium to high-end color still cameras employ three separate CCDs and processor channels to capture and process each of the primary colors — red, green, and blue — for high definition and sharpness and true color reproduction. Unfortunately, this costs more in both dollars and circuit-board real estate.

NuCORE Technology Inc., Santa Clara, Calif., however, just might have an answer to the problem. It developed a chip set that amplifies the R, G, and B-color channels separately, but pipes the signals into one channel for processing. The chip set makes possible a hybrid camera — a single appliance that can be used as a high-quality still camera and a high-quality video camera — all in one. It acquires, enhances, compresses, displays, and stores 4-megapixel silver-halide quality, digital still images continuously at 12 frames/sec, and 1.3 million pixel video at 30 frames/sec (full motion video) with 12-bit accuracy.

"Having one camera that can serve both functions has been regarded as the 'holy grail' of digital photography," states NuCORE's CEO Joe Raffa. "It's what digital camera makers have been trying to build for some time. Either they end up with a still camera that takes a few seconds of low-resolution motion, or a motion camera that takes poor quality stills — unsuitable for photo printing." The new chip set, however, can now provide the solution to both problems.

The chip set is composed of an analog front end followed by a digital processing chip. Much of the color balancing was moved from the digital chip to the analog chip which produces much higher image quality. Moreover, NuCORE increased the processing speed by moving the image-processing algorithms from software into custom-designed hardware in both chips. It has implemented a comprehensive set of algorithms to provide the highest possible image quality.

In spite of this, its hardware register is programmable to make it easy for camera makers to personalize their own designs through tuning. This means that one maker can set its colors for warmer tones, for example, while another can tune for a different tonal look.


For more information concerning digital photography, you may find the following Web sites helpful:

Canon USA Inc. (800) OK-CANON

Casio Inc. (800) 435-7752

Eastman Kodak (800) 242-2424

Epson (800) 289-3776 Fuji Photo Film USA Inc. (800) 378-3854 Konica USA Inc. (800) 285-6422 Minolta Corp. (800) 808-4888 Nikon Inc. (800) 645-6687 NuCORE Technology Inc. (408) 919-1820 Olympus America Inc. (800) 645-8160

Panasonic (800) 211-PANA

Polaroid Corp. (800) 343-5000

Ricoh Corp. (888) 742-6410

Sony Electronics Inc. (800) 222-SONY

Toshiba America Inc. (800) 829-8318

Vivitar Corp. (800) 421-2381


My uncle, Frank Gyorki, bought me a camera for my ninth Christmas. I remember clearly that it was an Ansco 620 with flashbulb attachment, so photography quickly became a very serious hobby for me. And Uncle Frank is a special uncle; he was a businessman who always owned a photographic company selling cameras and darkroom equipment, either wholesale or retail. This let him outfit his personal darkroom in style.

I had unlimited access to that exciting place. It was divided in two sections, one for developing film and the other for prints. What's more, I was able to test drive the latest cameras and film at no cost, borrowing them from his store. With a passion for taking pictures of everything I could think of, I spent a great deal of time in that lab, developing pictures for me and my friends. So much so that my mother complained that soon I would have mushrooms growing out of my head if I didn't go outside and play.

One of the drawbacks to that darkroom was that I had to learn how to make prints under the light of a red or yellow lamp. But I soon adjusted to it and was able to set exposure times and lens openings on the enlarger fairly well. I rapidly graduated to 35-mm film and maintained my love for black and white so I could still put my creative energies to use in the dark-room with toners and cropping prints.

I gave up the darkroom after graduating from college, and became content with professional photofinishers handling my work. But recently, my interest in developing prints was again piqued, and I began planning a darkroom. When I went to buy supplies, however, I was surprised to discover that now, computers are in and chemicals are out. Digital cameras are the leading-edge technology.

So I chose to write the article on digital cameras. Fortunately, Olympus offered me a digital camera of my choice to evaluate, but I wanted Uncle Frank's opinion, too. Although retired, he still takes award-winning pictures. "Well," he said, "consider the factors that can give you the kind of pictures you want, such as resolution, compression, storage, lenses, LCD preview screen, and through-the-lens viewfinders." After some investigation, we selected the Olympus C-3030ZOOM which lists for $999.

This turned out to be an excellent choice for several reasons. First, it cost what I expected to pay, and it sports all the features I need. For example, it has a 3.34-megapixel CCD with color LCD viewer. Moreover, Olympus says it's formatted at 2,048 1,536 pixels in length and width for maximum resolution. Not all camera makers advertise this quality, but this lets you compare digital cameras based on the actual pixels that make up the picture. (Check out the example calculations in the article.)

Another specification that some makers don't disclose is optional resolution modes available in pixels, such as Olympic's 1,600 1,200, 1,280 960, 1,024 768, and 640 480 modes. Uncompressed TIFF files store only one picture on the 16-Mbyte card that comes with the camera, but six pictures on an optional 64-Mbyte card. However, scaling down to 640 480 on a 16-Mbyte card stores 17 pictures and 68 on the 64-Mbyte card. But JPEG compression on a 16-Mbyte card can store six to 20 pictures at 2,048 1,536 resolution and 11 to 31 pictures at 1,600 1,200 — all the way to 66 to 165 pictures at 640 480 resolution.

The C-3030 comes with a zoom lens, both optical and so-called digital. There is a big difference between them. Optical zoom changes the focal length as is done on 35-mm cameras. But digital zoom processes a smaller image from the CCD and makes it look like it zoomed in. Moreover, it's hard to compare zoom on a digital camera because the image size in the CCD is smaller than the 35-mm camera. Some digital cameras take optical lenses for increasing focal length or wide-angle coverage. And for close-up work, check out the "macro" mode. Few cameras actually provide true focusing down to a few inches such as the 8-in. length in the C-3030. And not all-digital cameras let you compare sizes to 35-mm cameras such as the Olympus does. For example, the Olympus lens is 6.5 to 19 mm, at F-2.8, and contains six elements in eight groups, which is equal to 32 to 96-mm lenses on 35-mm cameras.

Alas, the Olympus C-3030 has many more features, too numerous to mention here. But my mind is made up, I want a C-3030. Thanks for your help once again, Uncle Frank.

Senior Editor

TAGS: Recreation
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