Thursday, 9 February 2012

Scanners Versus Digital Cameras for Preserving Genealogical Documents and Photos


About two years ago, I wrote a post entitled “Scanners Versus Digital Cameras for Preserving Genealogical Documents and Photos.” The time has come to update that post with the technological changes made in scanners and digital cameras since the date of that post. This post does not necessarily replace what I wrote previously, but highlights the changes in the last two years. Concerning scanners, for genealogists, the biggest change has been the introduction and promotion at genealogy conferences of an inexpensive portable scanner. In cameras, the resolution of inexpensive cameras has increased dramatically and higher-resolution built-in cameras are routinely included in smart phones.
One of the developments I have been watching for the past few years is whether or not digital cameras could produce images with the same resolution and quality as flatbed scanners. If you were to try to compare the two different methods of preserving documents and photos merely by reading the specifications for each type of device, you would soon become hopelessly confused. Scanner manufacturers claim resolutions in excess of 9600 dots per inch (dpi) while camera manufacturers focus on mega pixel (MP) counts, with commonly available cameras promoted at resolutions of 21.5 MP. Unfortunately, neither of these methods of measuring resolution tell us much about the real quality of the images produced by the different devices. Here are several rules to follow when making a decision between the claims of different devices.

Rule #1: The quality of an image produced by cameras depends on the lens more than the number of mega pixels.

Think for just a minute. The image produced by a camera always goes through the lens before it hits the sensor (where the film used to be). So even before you get concerned with the resolution of the sensor of a camera, you need to be concerned about the quality of the lens. Can you really expect the same quality from a tiny 1/4 inch lens in a smartphone as you can get from an expensive high-quality lens on a single-lens reflex (SLR) camera? This difference in the quality of the lenses does not mean that the smartphone camera will not take an “acceptable” image; it does mean, however, that the more expensive lens will produce a much higher quality image.
One challenge with comparing images produced by an inexpensive smartphone camera and one produced by good quality SLR camera and lens is that the differences are subtle and sometimes take years of experience and education in the area of photography to discover. In addition, we have a relatively long history of film photography and it is only recently that digital photography has achieved a measure of the quality and resolution of film cameras with high quality lenses.
Here are several articles, some of which date back a few years, discussing the difference between digital images and those produced on film:
If you read any of the above articles, or similar ones, and focus on the date of the article,  you will begin to see how digital technology has rather quickly overcome the quality of film cameras. There is no question that today’s inexpensive point and shoot digital cameras, by and large, have a much higher quality than the inexpensive film cameras of the past. You can still find a really bad digital camera, but most of the major manufacturers have produced acceptable quality cameras. The quality of the inexpensive digital cameras has dramatically improved.
But what about the lenses? The technology of digital vs. film has not directly affected the lenses. Overall lens quality has improved because manufacturing techniques and standards have risen, but newer high-end expensive lenses are not necessarily dramatically improved over some of the lenses of the past. As I noted, improvement has been most dramatic in the less expensive cameras and lenses. If you want to improve the quality of your images, you have to improve the quality of the lens as well as look at the resolution of the sensor.

Rule #2 The quality of an image depends as much on camera technique as well as the resolution of the camera and quality of the lens.

We have all seen really bad photographs. I have known some well-to-do camera enthusiasts who had the money to purchase the best and most expensive equipment, but never seemed to take a good picture even of simple subjects. The technical aspects of making images of documents and historical objects are just as important as the equipment. The best equipment in the world will not help you make good images if you don’t know how to use the equipment and utilize proper and appropriate settings and methods of photography. Digital devices are really computers in disguise. You need to know how to use the equipment whether it is a mobile scanner or a digital camera. If the image is blurry because you moved the camera while taking the picture there is no way to compensate for an out-of-focus image. Use a tripod or other stabilization device and make sure the image is in focus before taking a picture.

Rule #3 When buying a scanner be aware of physical limitations of the devices.

As I mentioned above, scanner manufacturers claim exorbitantly high resolutions for their devices. However, there is a physical limitation of the actual resolution, and that is the number of physical imaging elements, either flourescent, LED or LCD elements, sometimes mis-named the optical resolution. As time goes on, the resolution claims get higher and higher but the actual sensor count has not risen so dramatically. The higher resolutions are usually extrapolated by software and do not really increase the amount of detail available.
It is sometimes really difficult to determine the actual physical (or as is commonly described the “optical”) resolution of a particular scanner. For example, the technical specifications for a very popular mobile scanner do not tell the number of scanning sensors and this is not unique; for most scanners, you have to dig into the technical specifications to find the real optical resolution. The claims that a scanner will scan at a certain dpi is only useful if the number of physical sensors supports that resolution. Another example, the Canon 9000F Film Scanner, advertises 300 x 300 and 600 x 600 dpi resolution in the technical specifications, but in advertisements the resolution is claimed to be 9600 x 9600 maximum color resolution for film and 4800 x 4800 for documents. Canon also claims 19,200 x 19,200 (interpolated) for software enhanced scans.
The main difficulty in comparing digital devices is that the images you produce are usually displayed on a monitor or other screen at a resolution far less than 300 dpi so that it is even more difficult to tell what you are getting. For more information you may wish to read “My scanner has a resolution of 9600 x 1200 dpi –what do those numbers mean?” for a short introduction to the issues.
As you can see, comparing two different imaging devices is not as simple as it might seem by looking at the ads. Since my last post, digital cameras have increased in imaging quality at all levels while scanners have remained pretty much the same, although the claims would lead you to believe otherwise. There has been an increase in the quality of scanners through the use of LED and LCD light sources but the changes are mostly in power usage and speed rather than image quality. The answer is usually the same to any question about technology, you need to do your homework.

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