September 1998 Volume 20 Number 3
September 1998 Volume 20 Number 3
So you think it's time to look at digital cameras. O.K. Fine. What can you do with a digital camera that you can't already do with your trusty old Nikon? Is it better to have a digital image or a film image? The answer lies not so much in the taking of the image but in what you plan to do with it afterward. A digital image may be fine for some things and totally wrong for others.
What do you gain by using a digital camera? First, you eliminate the need for film and eliminate the cost of developing your photos or slides. While there is little cost advantage over the short run because of the initial investment, over a number of years you will save on film and processing costs. Second, you know instantly what your picture will look like. You can retain your good photos and trash the rest at the time you are taking them so you can avoid the hassle of extensive bracketing to assure a good shot. Third, you have an image that can be instantly utilized. It can be loaded onto your computer and sent to a colleague, be put on your web page or printed out and given to a client. Last, you have an image that can be manipulated and annotated if you have the appropriate software. One of the most important benefits of digital photography is that you can create images that will display more information instantly than a plain photograph.
What do you give up by using a digital camera? Resolution! Resolution! Resolution!
I suppose it is time to get a bit technical here. Digital images are long lists of numbers arranged in a grid. Each number represents one color dot, called a pixel when referring to cameras, or dot when referring to monitors, printers and scanners. In digital imaging, the resolution is defined as the number of pixels that an image contains. This number can be an absolute value (an inexpensive digital camera typically has a resolution of 640 x 480 pixels), a total absolute value (the same camera has 300,000 pixels, just 640 multiplied by 480), or a relative value (an inexpensive scanner might have an optical resolution of 600 x 300 dpi - dots per inch).
The number of colors each pixel can represent depends on how many digits long the number that represents the pixel is and is referred to as the bit depth. A bit depth of 8 produces a pallet of 256 colors, 16 bit will give 65,000 colors (often referred to as thousands of colors), and 24 bit color can represent over 16 million colors per pixel (millions of colors).
How does this compare to film? The equivalent digital resolution of a 35mm color slide can be as high as 4,800 x 3,500 if taken under ideal circumstances. A 4x5 would be 14,000 x 17,500 and an 8x10; a whopping 28,000 x 35,000 or over 980 million pixels. Using these numbers, an 8x10 image at a bit depth of 24 (millions of colors) would take 2.9GB of disk space (uncompressed), roughly 4.5 CD ROMs, or about 490 million words, if you are literally inclined.
To begin; as of August 1998, digital images taken with cameras costing less than $10,000.00 will not produce a photograph that is the digital equivalent of the fine grain of a film image produced by your old Nikon. Take heart though, one of the basic truths in digital technology is that price comes down exponentially once a technology proves popular. So don't despair. What is out of your price range today may soon be a lot cheaper. Also, much of the information contained within a fine grained photograph is glossed over by the human eye so the question remains, how much resolution do you really need?
Digital cameras which currently fall in the $800 to $1000 price range appear to most closely resemble the typical single lens reflex camera used by conservators. Typical resolutions for these cameras range from 1152 x 864 pixels to 1536 x 1024 pixels. Many have macro capability, additional lenses and some have partial manual control. If you are a hopelessly point and shoot type, this type of camera is available too, and many are significantly less expensive than the more elaborate ones, though the resolution is typically not as fine (e.g. 640 x 480 pixels), you have fewer options, and you have less control over how the image is shot.
For conservators buying a digital camera, the highest affordable resolution is probably best, but it is not the only criteria. You must also consider the quality of the optics, zoom and macro options, accuracy of the view finder or presence of an LCD preview screen, and, critically, how well the whole thing works - Are the colors true? Is the image sharp? Your choice of software will also have an influence on the final image so the camera's resolution does not automatically translate into a better photograph. If possible, you need to look at examples of photographs from each camera you are considering. Try contacting the camera company and asking for samples, but be aware that the samples you get will be the best the camera and their software can produce and may not reflect your own system's capabilities. Manufacturers web sites are good places to find information on any type of digital equipment.1
With digital images, you give up the guarantee of the archival permanence of a black and white photograph stored under optimal conditions. There is no such thing as an original digital image. They are infinitely copyable, with no loss of image quality. The first print is as good as the last. However, for digital images to have permanence, the picture file must continue to be accessible for future generations. Instead of worrying about perfect photo storage conditions, you now have to worry about transferring archived images to new file formats as technology changes. Remember the 8 track tape and the beta video recorder? Many people are also concerned about the absolute life of the storage devices we use today. High density magnetic storage devices (Jaz, Zip and even floppy disks) may not last for much more than 10 years. There is active debate on the estimated longevity of CD-Recordable disks, MO disks and other mass storage devices.
The most important question to ask yourself when you consider the transition to digital photography is: Do you need a film quality photo? In many cases, the answer is yes. In others no. It all depends upon the primary use of the photo. There are many uses for an image without the fine resolution of film. Are you putting it on your web page? For that purpose, you only need a resolution of 72 dpi. Anything higher than that can't be resolved by your computer monitor. Are you sending a file to a colleague to consult about a problem? His or her monitor can't resolve anything more than 72 dpi either but he might want to print out your photo to study it, so you can send him a file with more detail. A good photo quality printer resolution falls between 600 x 600 dpi and 1200 by 600 dpi. If you send a photo at these resolutions your colleague can see more detail in the print or enlarge the photo somewhat on his computer to view small details and it will still remain a decent image. This level of resolution works reasonably well on your own prints if you are printing images to include in a report for your client.
Do you need a photograph which will show very subtle changes in an artwork or do you need to enlarge the image significantly? It is here where you may run into trouble. When a digital image is enlarged, you will eventually encounter a phenomenon called pixellization. When this happens, instead of a smooth transition between two tonal areas of a photograph, you see a stepped effect or a series of squares. Obviously this is unacceptable in a conservation image where you are trying to convey information, though it might be rather interesting if applied to your own artwork.
Do you need a digital camera, or would a scanner be a more useful tool? Today's scanners will scan your current photographs at higher resolution than a typical digital camera can provide and they do it for a fraction of the cost of a good digital camera. In addition, you are not limited only to future photographs, but can digitize all of your old photos as well. Many of today's inexpensive flatbed scanners will scan both photographs and slides and produce a very good image. However, even dedicated slide scanners which produce superior digital images of your slides and which have traditionally been extremely expensive, have recently dropped dramatically in price. If your archive is primarily in slide format, then these machines will produce the most detailed images of your slides. No scanner will take new photos for you so it doesn't replace the old Nikon or a digital camera but if you are interested in having both film images and images you can manipulate or print then a scanner is a viable alternative.
Are you operating an old clunker of a computer? If so, forget digital photography. You will need a reasonably fast, high powered machine with lots of memory to use imaging software like Adobe Photoshop® and to effectively manipulate digital images. Digital images of any reasonable detail take up a tremendous amount of space in your machine, both when you are working on them and when you need to store them. A slow computer with little memory will make you crazy, even if you can get it to do the job. Some Macintosh computers have a slight edge over Windows computers in terms of their ability to deal with images easily, but today this is less of an issue than in the past.
Do you have a black and white or a color printer? Is it important to you to print color images? Is color accuracy an important part of what you are documenting? Monitor color, and printer color are not necessarily the same and the actual color of the art object may be different from both. There are computer programs which can be used to calibrate your printer and monitor and they are really essential if you are serious about color correctness in your images.
What type of process does your printer use to print? There are basically three types of color printers, ink jet, dye sublimation and laser in order of least to most expensive. Each produces a slightly different type of image.
Color ink jet printers produce photographs at a reasonably low cost. They are sometimes grainy looking, especially if they are printed on ordinary laser paper rather than special glossy paper, and if they get wet the ink is prone to bleeding. They are good for experimentation, for temporary documentation and for general home use. Their resolution ranges from a low of 300 x 240 dpi to a high of 1440 x 720 dpi and they cost between $250. and $ 500. The cost per page for supplies is lowest also.
Color laser printers produce a more stable print but they are significantly more expensive, in the range of $2500. to $3500. and up. They also produce their best quality image on special glossy paper.
Recently, one company has brought out a third option, a dye sublimation printer priced at under $600.00 which creates a beautiful continuous tone image. Previous dye sublimation printers were priced in the $10,000. range. This may signal the start of lowered prices for these printers though the current cost per page is $0.69 so it would be quite expensive to make this printer the sole general purpose printer in a lab. A dye sublimation printer would be better used as a second printer devoted exclusively to the printing of images.
One last option for printing your photos is to have it done commercially by a service bureau. This will allow you to have your images printed at their highest resolution but you have to factor in the cost of the service. If you print a lot of copies, this can add up.
A digital image file is not small in terms of normal computer files. If you are planning to do a lot of imaging you will need a place to archive your files. The hard drive on your computer will fill up instantly, no matter how big it seems to you now. You will need additional storage. There are a number of alternatives. The least expensive option which does not require the purchase of new equipment is to place your images on high density floppy disks. Depending upon the image, you may get one or several on an individual floppy. Some images will be too large for a single floppy disk. If this is the case, you will need to compress the image, possibly resulting in some loss of information.
A more reasonable alternative might be to add a Zip® drive to your computer for about $200. The Zip® drive uses media which resembles an overgrown floppy disk holding approximately 100 times the amount of information on a high density floppy disk. Additional Zip® disks can be purchased as needed, costing between $10 and $15 each. Removable disk hard drives are faster and have higher capacities but are much more expensive (the Jaz® drive's removable cartridges hold 1GB (gigabyte) or 2GB and cost $90 and $120) . Other options include adding a CD-Recordable drive to your computer and writing the image files to blank CDs (650MB per disk) which you can store like any other CD-ROMs. Blank CDs will set you back from $ 2.50 - $3.00 each.
A PHOTO CD Disc is a standard type of compact disc developed by Eastman Kodak Company for the platform-independent storage and retrieval of images captured by film and digitized by a film scanner. Since its introduction in 1992, the PHOTO CD Disc has become a de facto standard for high-quality, low-cost storage of digital images for the desktop.2 This product is another alternative to both digital cameras and slide scanners and is a useful storage medium for your digitized images. Kodak, saw the writing on the wall that for many purposes, film is dying, so they developed a system to master film onto recordable CDs at the time of processing. You can send your photos to Kodak to be developed and have them make you a photo CD at the same time. By doing this, you avoid the purchase of even more hardware because you can use the CD player that is incorporated in the new, powerful computer you just bought to manipulate the images.
Photo CDs come in two flavors, the standard and the Pro PhotoCD Master Disc. The standard photo CD contains up to 100 images, each at five resolutions ranging from a small 128 x 192 pixel "thumbnail" to a much more detailed 2048 x 3072 pixel version. All the scanned images are compressed using a special Kodak format. If you have the highest (4k x 6k) resolution scanned to a Pro PHOTO CD Master Disc you could get as few as 25 images on the disk.
Service prices vary by provider, scan format, and level of service (for example, consumer versus professional). You can find consumer scan prices ranging from US $0.50 to US $4.00 per image. The range in prices reflects a wide range of services. Some service providers may offer value-added services, such as film cleaning, custom scanning, etc. Also, a professional laboratory may offer scans using the advanced KODAK Professional PCD Film Scanner 4045, as well as additional services, such as encryption, watermarking, and advanced adjustments.3
The ultimate software for manipulating images is Adobe Photoshop®. It was the first successful software package created specifically for this purpose and it is still generally considered to be the finest. According to our survey of conservators it is the program of choice. It will run on either Mac or Windows systems. It is not cheap. It commonly costs $600, more if you add a vector drawing program called Illustrator®, but sometimes you can find them bundled together for about $700.
Digital cameras, printers and scanners will typically come with some form of digital imaging software that you can use instead of Photoshop®. Most will do basic editing such as cropping a photo to size, manipulating contrast and lighting and saving in common file formats. Some have additional capabilities like filters which are used to manipulate the image in random artistic ways. They can posterize, watercolorize or texturize as well as a number of other "izes". Adobe Photo Image® is one such program and is commonly referred to as Photoshop® lite. These programs do not generally give you the ability to create layers of different types of information within your files or to place extended textual documentation within the images.
If you do decide that you want a digital camera, a careful evaluation of each camera's features is in order. You have determined that digital images are useful to you, now here are some of the questions you should ask when shopping for a camera. What are the highest and lowest resolutions of the camera? How close can you get to your subject and still remain in focus? Does it have a zoom lens? Does it have multiple lenses? How accurate is the color? How much light do you need to capture an image? Is there a built-in flash? Can you turn the flash off? Can you preview the images in the camera or must you download them to your computer first? How many images will your camera store and at what resolution? Does it have a removable storage device or do you have to download the camera when it is full? Can you download some images without downloading all of them? Can you delete unwanted images when they are still in the camera or must they be downloaded to your computer first?
The last question to ask yourself is: Are you prepared to spend the additional money for the upgrade to your computer, the new software, the new printer and a storage device in addition to the cost of the camera?
Some of the answers to these questions can be found on line in the form of comparative reviews by searching the web. Cnet.com http://www.cnet.com is one useful site for reviews of all types of digital equipment including on-line examples of photographs taken from a large number of digital cameras. Look at the sample photos and choose which cameras you think you might like. Then go to the web page of the company which makes the camera. Frequently, you will find extensive technical information and further examples of photographs taken with their products. An example of this type of page can be found at http://www.olympusamerica.com. The high resolution macro photographs are very impressive. There are also large numbers of books, some more technical than others, on digital photography and other related subjects. Check out the technical section of a good bookstore or look for a bookstore in your area which specializes in technical subjects.
The choice to incorporate digital imaging in your documentation is a very personal one. It is not necessarily an either/or decision. In today's information age, the ability to send a digital file anywhere in the world is a very powerful tool for the conservator. Digitally manipulated images can be used to provide more information within an image than conventional film. Condition reports created with digital images can convey a tremendous amount of information within a single photograph, eliminating the need for convoluted verbal descriptions of damage to the art object. The layering capabilities of Adobe Photoshop® can be used to document complex projects by placing different types of information on different individual layers. It is very easy to e-mail a digital photograph to a conservator half a world away to consult about a treatment, that is, if they also have a computer and e-mail. The luxury of having digital images incorporated into documentation databases is alluring. A thumbnail image next to the text in either a database or a document ties the text into the visual documentation whatever the form. Imagine taking a quick digital snapshot of every signature on every signed artifact you treat. These images could be incorporated into an artists' database, along with name and biographical information, and would become an invaluable research tool.
On the other hand, the digital world is expensive and there is no guarantee of the archival permanency of your printed images at this time. Given an unlimited budget, I can see the usefulness of having both film and digital imaging working side by side, each being used for the strengths it brings to the documentation process. Given a more modest budget, then choices have to be made and the only one who can make them is the individual conservator because only he or she knows for what purpose they are creating their images.
1. Some examples are: http://www.nikonusa.com, http://www.kodak.com, http://www.epson.com/imaging/ Besides technical information on their products, each of these sites contains images taken with their cameras to look at or download and print on your printer. Some of the macro shots are spectacular.
2. Lifted directly from the Kodak web page of frequently asked questions at http://www.kodak.com/global/en/service/faqs/faq1001a.shtml
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