Wednesday, December 12, 2012
Camera vs. Scanner -- Practical Considerations
In my recent posts on the subject of using a camera or a scanner for digitizing, I have primarily considered the issue of resolution. A film photograph is usually considered to be a "continuous tone" image. However, all film photographs ultimately have a "grain." The grain of the film is the microscopic crystals of the silver-based, light sensitive chemicals used to capture the image. The speed of the film is directly related to the size of these grains. The "faster" the film, the larger the grains, the "slower" the film, the smaller the grains. The speed of any particular film is represented by an International Standards Organization (ISO) number. A low speed or slow film might be ISO 100, a very high speed film might have an ISO as high as 1200 or even higher. The tradeoff for using a faster film was the increased graininess of the image.
Faster films were designed to take advantage of lower lighting conditions. In a studio or with a camera stand, the speed of the film or digital image is not an issue. You can use longer exposure times to compensate for any lack of lighting. You can also use studio lights to add light.
Digital cameras have borrowed the concept of fast/slow and most adjustable digital cameras can change the ISO number to increase or decrease the time it take to form the image on the sensor. There is the same tradeoff, higher speed equals grainy image and etc.
So, for any photograph, depending on the ISO number or speed of the film, there is an ultimate limit to the image resolution. Here is an example from an earlier post showing the graininess of the image at magnification:
If you click on this image and zoom in, you will immediately begin to see a mottling or graininess in the darker portions of the image. In essence, I have reached the physical limit of the resolution of this photograph.
The question is whether or not that extra amount of resolution is necessary to preserve the image? But what if we don't need to preserve the image at all. What if we only want to preserve the information in the image and not the image itself. For example, what if we are in a record repository and merely want an adequate copy of a document for our own purposes? Or what if we have letters or documents from our ancestors we want to share with other family members? Do we need to be concerned about all this technical stuff about ISOs and etc?
The answer is a little bit complex and depends on who you are and what use you are going to make of the images. If you were FamilySearch, for example, and were digitizing millions of images, you would want to make sure they all met some minimal standard, so that the images online would be as useful as possible. But if you are doing your own research and merely want a copy from a page in a book or some other document, why would you care? The main issue would be readability. (In fact, readability should always be the main issue, but that is another post).
So, if you are someone like me, making archive lever digital copies of photographic images, you will be concerned with the quality and resolution of the image. You will also be willing to spend whatever it takes to make adequately useful images. If that means spending $3000 or more on a camera body and even more on lenses, then that is what I will do. I will also use a camera stand, special lighting and anything else necessary to capture images. If I can get a higher quality image with a scanner, then I will purchase and use a scanner. And so forth.
But if all I need is a quick, readable copy, I may use my 8 Megapixel iPhone camera or a 12 Megapixel point-and-shoot camera.
I fully realize I live in a world that is completely foreign to most genealogists, especially those who agonize over the purchase of a $20 genealogy program. But here, as in everything else, there are tradeoffs. I could spend pages and pages listing the things that I don't spend money on at all of only very rarely. Like for example, going out to eat, attending commercial entertainment of any kind, purchasing expensive clothing, and the list could go on and on. My priorities are to preserve the images and documents I find as a full-time genealogist. At last count, I had well over 100,000 images with more being added regularly.
I am not saying any of this because I feel that anyone else should follow my example. But if you do have thousands of images to digitize, you just might want to start reorienting your priorities in order to afford the proper equipment. You may also wish to get started learning all of the complex photographic issues involved in making digital images at this level.
Where does that leave us with deciding between a scanner and a camera? The scanner wins, unless you are faced with huge numbers of scans, in which case, if your time is money, you can get similar quality at a much faster speed with high-end camera equipment. But don't assume that you can simply take a picture of a picture and get anything approaching archive quality without spending the time and money on the equipment.