PCSO Bulletin, Spring 2002 Mr. James Clark Lecture Summary

Digital Cameras

Presented by Mr. James Clark
at the 2001 Annual Session

Summarized by Dr. William Finnegan
Northern Region Editor

Digital cameras eliminate the expense of film and processing, waiting for the film to return from the lab, recalls to redo pictures and the need for dark room space.

Instead of film, digital cameras have silicon wafers called image sensors containing millions of light-sensitive diodes called photosites. Each of these photosites records the intensity or brightness of the light that falls on it. The brightness is then stored as a set of numbers in the camera’s storage media. These numbers are then used by the camera’s microprocessor to reconstruct the image on the camera’s LCD (liquid crystal display) screen. These numbers can also be downloaded to a computer for storage or processed by any number of types of software. There are two types of image sensors:

1. CCD (Charged Couple Device), which is more sensitive to light and gives a clearer image.

2. CMOS (Complimentary Metal Oxide Semi-conductor), which is less expensive to produce, (making the camera less expensive), and consumes less battery power. (He prefers rechargeable batteries, since they are more efficient and less expensive in the long run than replaceable batteries)

The more resolution a digital camera has, the better the image quality. Resolution is measured by the number of photosites on the image sensor. Each photosite represents one pixel (picture element) in the final picture. More and smaller pixels mean added detail and sharper edges in a digital photo. The advertised resolution of a digital camera is usually slightly higher than the actual number of photosites used for imaging. A small portion of the sensor area is dedicated to image processing components.

There are two kinds of image resolution. Optical resolution is true resolution because photosites are physical devices that can be counted and each photosite equals one pixel. With interpolated resolution software add pixels to an image by evaluating surrounding pixels. You have more pixels for a larger picture but less sharpness and clarity because no new information has been added.

Most digital cameras have 24 bit color, which produces 16.7 million colors that are almost seamless, that is, continuous in tone. With 3 to 6 million pixels each images file size is 9 to 18 megabytes. These are very large files and need to be compressed for ease of processing and storage. There are two types of image compression, lossless and lossy. Lossless compression such as LZW used in TIFF files allows us to compress the files to 50% without any decrease in the quality of the uncompressed image. Most digital cameras use Jpeg, which is a lossy compression scheme. Jpeg reduces the file size by reducing or eliminating repetitious data. Depending upon image quality we can compress an image 10:1 or even 20:1, thus saving a tremendous amount of disk space.

Jpeg can be used for email or web images, but high-quality images such as board photos should be manipulated and saved using lossless compression. After printing the final pictures the composite can be stored as a Jpeg to save hard drive space. It is very important to save an unaltered copy of your digital records on a CD or DVD. An LZW TIFF file or a high-quality Jpeg saved on a CD will be important to you if you ever want to publish the case or need it for legal purposes.

Image sensors in digital cameras record only the brightness of the light that strikes each photosite. They record one of 256 brightnesses or shades of gray. Color is developed from a red, green or blue filter that is incorporated into each photosite. The sensor separates out the three colors (RGB). The processor, in your camera, computer, or digital projector puts the three colors together using red, green and blue LCD’s in cameras, flat panel, laptops and projectors and phosphors in CRT (cathode-ray tube} computer monitors.

The way most of us judge our digital pictures is by looking at them on a computer screen. Image resolution and screen size are critical to picture quality. Today most computer monitors are XGA with 1024 x 768 pixels. Newer CRT and LCD flat panels are upping the resolution to SXGA with 1280 x 1024 pixels. Resolution must continue to improve as screen sizes increase or image quality will suffer.

With digital presentations becoming the norm it’s important to understand that the weakest point in today’s presentations is the LCD or DLP (digital light projector) projector, which will project 768,432 pixels. Some LCD projectors can project higher resolution, even high-definition television, but these projectors are very expensive. Some presenters purchase their own LCD projectors so that when they travel they ensure their presentations have quality images.

There are three types of digital cameras on the market: Point and shoot, Prosumer and Professional.

Point and shoot cameras can cost less than $1,000, but they are usually not adequate for high-quality dental photography. These rangefinder type cameras are designed for vacation photography and don’t have the controls or light source we need for our intra-oral views. For instance, most don’t have apertures, so you cant control the depth of field. Most point and shoot cameras can’t adapt a close-up lens, or an auxiliary flash for better clinical illumination. There are some newer point and shoot cameras (Nikon 995 and Fuji 6800) that have good macro (close-up) lenses, but the pop-up flash is not located close enough to the lens to eliminate shadows. The Nikon Coolpix 995 can be adapted to use the Nikon SB-29 Macro Speedlight. Another dilemma for the consumer is that the manufacturers seem to keep coming out with newer and better models every other week.

Prosumer cameras (a play on words between professional and consumer) will cost more than $1,000. These are single lens reflex type cameras, which you can adapt a close-up lens and an auxiliary flash. These cameras have manual f/stops, shutter speed and focus. They usually have some sort of built-in flash, but, not always in the best position for intra-oral views. Prosumer cameras have non-removable zooms lens that will shoot close-ups in the macro mode.

The FinePix 6900 features Fujifilm’s second generation 3.3 million-sensor Super CCD that generates a 6-megapixel picture file. It has manual aperture settings (down to f/11) and adjustable shutter speeds. A 35 to 210mm zoom lens and a TTL (through the lens) electronic viewfinder (LCD), which for our application is not as good as an optical TTL viewfinder. LCD screens need to be refreshed which creates a lag time, easily seen by moving the camera while looking through the viewfinder. Made of metal, it’s a quality piece of photographic equipment.

The Minolta Dimage 7 is very lightweight (made of plastic, so longevity may be questionable) and easy to handle. It has high resolution (5.2 mega pixels) for sharp images and has a very powerful zoom lens (7X zoom up to 250mm) with an extremely good macro feature. Unfortunately the lens only stops down to f/8 which at 250mm gives us very little depth of field. It is difficult to use intra-orally because of an electronic viewfinder and a metering system that seams, at times, at war with the Minolta Macro flash system.

The Olympus Camedia E10 has four mega pixels of resolution, manual and auto settings, including auto and manual focus. It‘s a true SLR with an optical viewfinder. You are looking at the actual subject through the lens rather than an LCD screen inside the camera. The latest version of this camera, the Camedia E20, has 5,000,000 pixels. With a fast macro zoom lens, a large LCD screen and the ability to fasten an auxiliary flash, this mid priced camera makes a good clinical camera.

Professional Digital Cameras are basically 35mm SLR camera bodies with image sensors replacing the film. They have the same controls as our 35mm cameras, so the learning curve is small. They are easily adaptable for dentistry because they use the same 100 or 105mm macro lenses and electronic flash systems. As a matter of fact, those using 35mm clinical cameras might already have the correct lens and flash for a digital system. They will be most expensive ($4000 and up for a complete system), and they give the best images. Three professional cameras that should be considered are the Nikon D1, the Canon D-30 and the Fuji S1 Pro (his favorite).

Once you have chosen your camera and taken some pictures, you need to get the images into your computer. All the new computers today have USB (Universal Serial Bus) ports. You can download the image directly into the computer through the included cable. Optionally, you can store the images on digital media, then transfer it to the computer. Examples: Smart Media, Compact Flash and IBM MicroDrive. For instance, the Fuji S1 Pro can put close to a thousand pictures on a 1 gigabyte MicroDrive. The camera converts 17.8 megabyte raw image files to 1 megabyte Jpeg’s. This means you don’t have to download everyday. Transferring images to the computer is as easy as plugging in a USB cable. Another device for downloading images is a card reader. Card readers attach permanently through a USB connection to your computer. Some manufacturers offer camera cradles that cable to your computer. Allowing you can download the images directly from the camera seated it its cradle.

Adobe PhotoShop is the best software program to manipulate images. It is expensive ($624, from Amazon), but you can find a smaller and somewhat less intimidating version, PhotoShop elements, for under $100. You can scan your tracings with a flat bed scanner and radiographs with a transparency adapter. PhotoShop allows you to dump or correct color, add or subtract contrast, lighten or darken, crop, rotate and enhance. With a slide scanner we can scan in all those old Kodachrome slides and save them on a CD. With a little practice PhotoShop will become your best friend in the digital photo world.

Microsoft PowerPoint allows you to make presentations with a laptop computer and a LCD projector. You won’t need to carry slides any more, and making those last minute changes are no problem.

Once you have digital photos saved in your computer or on a CD you can easily insert digital pictures in your letters by using the insert menu in Microsoft Word.

There are many photo quality printers on the market. Inkjet printers do a great job for a very small investment. The Epson stylist photo 820 for around $200, the Canon S-800 also in the $200 range and inkjet printers from Hewlett Packard, Lexmark and Kodak are all inexpensive with excellent results. Dye sublimation printers like the Olympus P400 at $1000, Kodak 8660 at $4800 give you very high-quality pictures, although both the up-front and price per page is considerably higher. When deciding on a printer, consider printing time, ink usage, picture and color quality.

There is considerable variation in cost. Buying paper at a computer store will cost more than at an office supply. Costco, both in store and on line offers 100 sheets of 8 1/2 x 11 photo quality for $8.99 and glossy paper for $19.99.

It is very important to save high-quality unaltered copies of all your usable digital photos. You can save hundreds of high-quality digital pictures on one CD (cost @ $.50) An inexpensive CD burner with a USB connection can cost less than $200 and a Firewire (IEEE1394) CDRW for around $300. Make a separate copy for offsite storage, in case something happens.

Editor's note: Digital cameras can now match the photo quality of a 35mm camera. As prices come down and image quality increases the professional digital camera may end up replacing the 35mm camera. Digital camera market share increases every year; the prediction is that digital will outsell film cameras this year (2002). The benefits of digital photography include seeing the results right away without waiting and the extra expense of processing.

On the downside, you need computers, software and all the accessories to process the images. The other problem or dilemma would be the constant improvement in the industry, that is, do we buy now, or do we wait for the price to go down? Are you willing to accept an average picture, over a high-quality image? If you have more than one staff person using the camera then simple might be better than high tech. The thought of having a clinical camera being easily converted to a holiday camera by changing lenses might also be a consideration. A daily update on digital equipment can be found at (stevesdigicams.com) or email clarkj@uwashington.edu. Telephone: (206) 543-5724.

Spring 2002 Presentation Summary:

Digital Cameras