This is part two of the comparison between single lens reflex cameras (SLR) and point and shoot cameras for use in genealogical research and for taking family pictures.
The next consideration between the two types of cameras is as follows:
What about the quality of the picture? Digital cameras are just that, they make pictures by focusing the light onto arrays of little tiny sensors that convert the image into dots called pixels. If you magnify (zoom in) a digital picture, eventually the picture will become pixelated, that is broken into small square dots. On the other hand, photographic film has a continuous gradation of light and shadows created by microscopic grains of chemicals, usually involving silver. If you magnify a film photograph, you will see less detail but unless you use a microscope, you will probably not see the grains. Digital cameras are just now beginning to overtake film cameras in the detail of the pixels and compared to the microscopic film grains and only at the very high end.
The resolution (i.e. the size of and number of pixels) of digital cameras is measured in megapixels. See previous posts for an explanation. Generally, the higher the number, the higher the resolution and the larger print that can be made with high quality. For example 10.1 is a higher resolution than 6.0.
What resolution do you really need to do adequate pictures for genealogy? The answer depends on your own preference. I found that I was dissatisfied with digital photos of documents and books until the cameras reached over 6 megapixels. At 10 megapixels or more, the images begin to rival flat bed scanners in their overall detail and quality. Presently, the resolution of most of the cameras available, except the very cheapest, are adequate or more than adequate for genealogical use.
What about keeping documents in focus? When taking pictures of documents, particularly books and other items that may not be flat. It is possible that part of the image will be in focus and other parts completely unreadable. Without getting into a technical discussion of depth of field, this problem can be overcome, to some extent, by making sure the camera is at a 90 degree angle to the document and that it is far enough away from the page to capture the whole image in one frame. After taking the picture, most cameras have a function where you can view the image on an LCD screen and even zoom in to see if the picture is in focus. It is a good idea to check the photo after each shot unless you do not move the camera.
What about light sources? In order to take usable pictures you must have enough light to see the detail you are trying to document. Sometimes that means using a flash. Most of the cameras, both point and shoot and SLRs, come with built in flash units. However, when used to take pictures of documents, the flash has a tendency to reflect off the page and cause hot spots with obscure details in the photo. I take almost all my photos of documents with available light rather than a flash, and when necessary, if the light is too low, I use a tripod or brace the camera against a desk or table to take a longer exposure to compensate for the lower light conditions. Do not automatically use a flash whenever the camera decides it is necessary. Most of the time the photos will come out with better light without a flash. But remember you are risking camera movement from a slower shutter speed and therefore, blurred pictures. Because you have greater control over all of the aspects of the camera, if you want to have that control, you will do a lot better with a SLR camera.
If you have any particular questions about using a camera to record documents in a particular repository, make sure the directors of the repository have no objection to the use of your camera before getting in trouble.
I will have a post shortly on taking pictures of microfilm images. Stay tuned.