How to digitize photographs

How to digitize photographs

Becoming digital archivist as a professional requires different skills. You are expected to be curious and accurate, partial treasure hunter, partial magician. Those who are involved in creating images for digital collections have to understand how the camera works at least on basic level. Life-time learners definitely benefit in this field.

In this blog I’d like to share some thoughts on digitizing photographs and prints as one of the most popular questions I get.

Before proceed let’s define prints and photographs. 

For purposes of this post these subjects include photographic prints, graphic-arts prints (intaglio, lithographs, etc.). Please note that working with photographic transparencies such as slides, negatives and Kodachromes  varies from listed below. We will dig into them in next posts.

The intent in scanning photographs is to maintain the smallest significant details. This leads us to the “resolution” of digital image which  is  quite mystery concept for new comers.

Image resolution is the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail.

Image resolution can be measured in various ways. Resolution quantifies how close lines can be to each other and still be visibly resolved. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch), to the overall size of a picture (lines per picture height.

Fine art photographers deal with resolution when printing pictures, say, for a show. We also face the term when  check the cell phone camera or buying new one (which typically does not make any sense for personal use). Resolution requirements for photographs are often difficult to determine because there is no obvious fixed metric for measuring detail such as quality index. Additionally, accurate tone and color reproduction in the scan play an equal, if not more, important role in assessing the quality of a scan of a photograph.

The recommended digitization specifications for photographs take into account the intended uses. 

Every generation of photographic copying involves some quality loss, using intermediates, duplicates, or copies inherently implies some decrease in quality and may also be accompanied by other problems (such as improper orientation, low or high contrast, uneven lighting, etc.).

In general, 300 ppi at the original size is considered minimum to reproduce the photograph well at the size of the original. For photographic formats in particular, it is important to carefully analyze the material prior to scanning. given that  I learned from experience and established guidelines to consider 400 and 600 ppi when it comes to high level of performance, long term preservation, and creating master files for well ordered digital archive.

Such resolution however effects the choice of digital storage facilities. Definitely something to remember when putting together family archive.

Resolution effects not just the amount of details, but the choice of digital storage facilities.

Prints and photographs encompass a wide range of technologies and processes that have been used to create reflective images. 

For many of these, subtle texture, tone and color differences are an essential part of their character. 

While it is not possible to preserve all of these subtle physical differences in digital form, we can approximate some of their unique qualities. It is for this reason that all master files from both color and black and white originals are to be imaged in 16 bit color at or above. 

The use of glass or other materials to hold an image flat during capture is allowed, but only when the original will not be harmed by doing so. Care must be taken to assure that flattening a photograph will not result in emulsion cracking, or the base material being damaged. Tightly curled materials must not be forced to lay flat.

Generally it is allowed the use of flatbed scanners when imaging photographs, but the archivist should be aware that images may render differently on a flatbed scanner than if imaged using a camera or 35 planetary scanner and traditional copy lighting. Additionally, when using a flatbed scanner, dust and dirt on the scanner glass can result in dust and dirt in the file. Given that adjustments to correct or enhance the image may be made to access versions, and noted as such in embedded metadata and file naming.

Color and tone adjustments must be made to the target data, not the photograph.

A reference target should be imaged with each exposure and retained in the master file.