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Monday, July 29, 2019

The Ultimate Digital Preservation Guide, Part Seven -- Technological Challenges: Cameras

I was recently watching the documentaries about Apollo 11 moon landing and I began to notice the technology and all the things that were missing and all those we no longer use. I could write pages and pages about the changes from 1969, but I don't have to go back that far to see other major technological changes. Genealogy is certainly not immune to technological change. Theoretically, you could still do genealogical research with a pencil and a few sheets of paper. But there is an almost certain possibility, assuming you wanted to try, that you would be repeating the work of other researchers.

It has been some time now since I talked to a person who was a confirmed technological holdout. Although there are still a considerable number of people who line up at the door of the Family History Library in Salt Lake City, Utah every day it is open pulling huge suitcases full of documents and paper.

Because of my constant digitization efforts, I show up at the library with a laptop, a flash drive (thumb drive) and a smartphone with a camera. I usually forget to bring a pencil or a pen. Granted, there are still some archives and libraries that are living in the Dark Ages and prohibit cameras and even some who prohibit computers, but usually, those three things are all I need to take notes and do all my research. Because I am digitizing everything I find and entering the information into an online family tree program such as or, I am not creating any more paper files than I already have. I am moving directly from research to digital preservation. Also, all my photos are now digital and so I do not have any new paper photographs.

But realistically in this series, I have to write about paper. There are two main ways to digitize paper records: cameras and dedicated scanners. In this post, I am going to write about digital cameras as they may be used for document preservation.

Some professional-level document preservationists are never satisfied with the quality and resolution of the digitized images. Every time there is a technological change that increases the resolution of digital cameras, there is a move to make that level a new standard. It becomes difficult to believe that they put up with microfilmed images for so many years when you find out about their strict requirements. Although websites such as have explored the possibility of incorporating private digital collections, they have been stopped by the complexity of the laws governing their publication online.

One major challenge for private preservationists is finding a place that will host the digital images. I have been fortunate in finding university special collections libraries that will agree to host and preserve some of my collected items. But normally, you will find very little interest in either the paper or the digital copies outside of immediate family members.

Paying others to do the physical work of preservation and then finding some entity to host either the paper or the digital images or both can be very daunting. There is a certain amount of physical equipment you will need to do an adequate job of preservation.

From a physical equipment standpoint for preserving records, we presently have digital cameras with very high resolution that exceeds the resolution of even the highest grain photographic film. For example, Sony just announced a professional level camera body the Sony a7r IV with a 61 MP full-frame sensor. The initial retail price of the Sony a7r IV is $3,498.00, far less than an equivalent commercial digital camera with a lower resolution sensor. The Megapixel race is just beginning.

The terminology used by the manufacturers of digital cameras still has a lot of baggage from the days of photographic film. Two terms are pertinent to any discussion of the resolution of a camera whether digital or film. The two terms are Grain and ISO.

ISO is an acronym for the International Organization of Standardization that indicates the film speed or reaction time to light. Another commonly used acronym for film speed was the ASA (American Standards Association). The higher the ISO or ASA number, the more sensitive the photographic film was to light. However, there was always a trade-off. Very high ISO numbers usually resulted in grainier photographs or photographs with a loss of resolution. A fast photographic film had an ISO of 600 or even 1200. The ISO number has been applied to electronic sensors for digital cameras. Here is an example of a grainy image.

Inside a digital camera, the electronic sensor takes the place of the photographic film. The resolution of the sensor is roughly equivalent to the number of individual sensor elements measured in megapixels or one million or exactly 1,048,576 pixels. So, a 20 MP sensor has more pixel or sensor elements than a 12 MP sensor. Many consumers automatically assume that the higher the Megapixel count, the better the image. In fact, there are some physical limitations that make higher and higher Megapixel counts less important than you might think.

Many digital cameras also advertise high ISO numbers for their sensors such as an ISO of over 1500 but the inevitable trade-off is grainy photos. The new Sony A7R IV has an ISO that goes up to 102,400 far higher than was ever possible with film. With that high ISO number, you could almost take photographs in the dark, but the results are usually an increase in grain. If you want to see an interesting phenomenon, stand about five feet away from the image above and you will likely see nearly all the grains disappear.

For digital preservation, a low ISO, such as 100, is the most desirable. For this reason, it may be necessary to illuminate the items being photographed so eliminate shadows and to provide the light needed for the low ISO number. The ISO number is usually set manually on the camera by the photographer.

When you are using a camera for document preservation you need to remember that the standard used by the Library of Congress for resolution is usually measured in dots per inch or DPI. The standard right now is 300-400 DPI. How does the Megapixel (MP) count translate to DPI? Good question, it doesn't really work that way. 300 DPI is the resolution of a good computer printer. Taking this any further begins to get really complicated but I will try to simplify the differences.

There are three ways to measure optical resolution: DPI (dots per inch), PPI (pixels per inch), and LPI (lines per inch). Here is a website that will convert measurements between some of these different systems: DPI and PPI are essentially the same types of measurement. LPI is used primarily by printers and some engineers. Those who are doing professional level digitization use LPI targets with graduated lines to focus their cameras. Conversion from LPI to DPI is done by multiplying by 16. For example: 150 LPI x 16 = 2400 DPI. Of course, you can change DPI to LPI by dividing the DPI number by 16. Here is one type of focus screen used in early TV broadcasts.

Surprisingly, the answer to the question of how much resolution is practical and necessary is fairly easy to understand and that is why the number 300 in DPI keeps coming up. First, we have to start with the resolution of the human eye. At a distance of one foot, the average person's eyes can only resolve details at about 89 microns the equivalent of about 300 DPI or PPI. In short, any higher resolution than about 300 DPI or PPI is lost to the human eye. This explains why the Library of Congress standard for resolution is 300 dpi.

The DPI resolution of your digital camera depends on the physical size of your output. If you want an 8.5 x 11 print at 300 DPI, you need a digital sensor that takes images at about 7-8 MP. That Sony 61 MP camera will produce about a 24 x 36-inch image at about 300 DPI. These numbers assume an ISO of about 100 which is somewhat the standard for high-quality photos with good light. When you view an image on a computer screen or TV. If you need to use PPI as the measurement. 300 DPI is about 118.11 PPI.

What does all this mean for genealogists who don't care to become professional photographers? If you are serious about using a camera for digital preservation, you need to have one that has at least a 20 MP sensor. Otherwise, stick to using a flatbed scanner. You can now buy a good 20 MP+ camera for around $500 - $600. For example, see the Sony Cyber-shot DSC-RX100 III.

When you have a camera is it also a good idea to have a tripod or camera stand to hold the camera steady and in some cases, provide light. Here is one example of one type of camera stand:
There are a few more accessories that can help with your work, but there are also a lot of diy projects that can are online as substitutes for spending money.

If you are merely uploading documents to an online service, such as Memories section, you will need to look at some of the photos already online and see that hardly anyone cares enough about the quality of their images to worry you too much. Remember one basic rule. You can't get any better quality than your eyes can see.

Here is the summary of my suggestions for digital preservation using a camera:

  • Use a digital camera with a 20 MP sensor but use what you have instead of waiting to digitize your records
  • Find a way to stabilize the camera at a fixed distance from the artifacts or documents being digitized
  • Set the exposure at 100 ISO and make sure the artifacts or documents are in focus
  • Upload the images to an online website such as Memories and attach and tag them to the appropriate ancestors
There are a lot of other things to know, such as how to use computer photo software such as Adobe Photoshop, but there are also a lot of less expensive alternatives. More coming in this long series. 

See the previous posts in this series here:

Part One:
Part Two:
Part Three:
Part Four:
Part Five:
Part Six:


  1. One advantage of imaging at a higher resolution than the eye can see is that this gives you the ability to zoom in on a certain portion of the overall image without the image resolution suffering.

    1. However, you cannot manufacture resolution. You are always limited by the resolution of the original document or photograph.