The Scanning Project-7: How a Scanner Works

While this may be purely of academic interest, I thought it would be a good idea to demystify scanner mechanics a bit. Think of a scanner as a potentially high megapixel imaging device that converts image information from film or prints to a digital file. Just as in a digital camera, the image can be manipulated during the conversion process and given certain attributes, such as correction of color and enhancement through contrast and saturation choices.

For those who have not worked with a digital camera a scanner is akin to a copier. But the scanner does not have toner or nozzles to lay down the copied information; it creates digital image information that can be manipulated to mimic the copied image or to enhance or adjust as needed.

This Epson 850V scanner scans both prints and film using a flatbed design. This illustration shows slides in the film holder, which is then placed directly on top of the platen. 

In essence, a scanner contains an RGB sensor, just as in a digital camera that, in flatbeds, sits underneath a glass covering onto which the material is placed. Flatbed scanners have both fixed and movable mirrors and a movable light source. The movable mirror and light scan across the surface of the image and direct the results through a lens to the fixed mirror, which directs it to the RGB sensor. In essence, it “writes” the information as it goes. Depending on the quality of the scanner, the light source in a flatbed can be LEDs or some variety of a tube of light.

Film scanners differ slightly in how the image is captured. Strips of film or mounted slides are put into a holder that is then inserted into a slot in the scanner. In a flatbed the film is placed onto the glass platen within holders. When an image is selected for scanning in a dedicated scanner a stepper motor moves the frame across a lens that directs the image to the sensor.

Here's a Plustek dedicated 6x6cm film scanner. Frames and strips are placed into a holder that is then inserted into the film gate, which then "steps" the image across the scanning module. 

While the mechanics of a scanner are fairly straightforward, the software and capabilities of the sensor can vary considerably, depending on price and manufacturer. In the next posting I will offer some criteria that should be used to choose a particular scanner for the work you have in your collections. Scanner specs are important to understand as they will determine what you can and cannot accomplish in your work.

Every scanner works in basically the same fashion and there are a number of steps required prior to making the final scan. The first is a preview, a sort of large thumbnail (not full resolution) image, often called a “prescan.” While it serves as a rough guide to the image it should not be taken as what you could or should expect from the final scan, just as the image review on your digital camera’s LCD is certainly not what you will achieve after image processing later.

Once you have the prescan on the screen you can make various adjustments. The heart of the scanning process is the software through which you process the image. This involves choosing the resolution, the bit depth, noise reduction, dirt and scratch elimination, dynamic range, color balance and more. These choices will be examined in detail in the scanner workflow postings of this project.

Here's a screen grab of Epson's scanner software with many of the control modules opened. Image controls in software can be basic or quite sophisticated, but most allow you to make the kind of adjustments you need to create a good quality image file from the film or print you are scanning.

The changes you make to the prescan is where you set up the parameters of the scanned image, much as you set up the image-processor in a camera to deliver a certain look and resolution of a captured image. Scanning software can be quite sophisticated, and learning about its many options is key to creating quality image files from the original material.

By understanding what a scanner can deliver, and what program to utilize to get the best possible results, you will be well on the way to making the right buying decision and accomplishing your goal of archiving your precious film and print images.

Next posting: Scanner Specs

The Scanning Project-2: Outline

2) An Outline

My approach to this project is not overly technical, yet some technical discussion is unavoidable. I have always regarded technical matters as more “benefits” than the technical “thing” onto itself; in a sense mine is a practical approach and in that way hopefully accessible and applicable to anyone who wants to take on a similar task.

This project is not aimed at archivists at large institutions who have access to very high end scanning systems, but is more suited to those with medium-size image collections who want to digitize their film work within a budget and with equipment that does not require an advanced degree to operate. It is also aimed at those who remain dedicated to film capture but want to output on inkjet printers or for web albums. The procedures discussed should also be useful for small museums, historical societies and collectors who have  negatives, prints and even glass plates and want to preserve and perhaps enhance those images. That’s why I will include a section on print and larger negative scanning procedures as well.

Scan from a 6x7 Fujichrome shot in 1996 made on a flatbed scanner. Dedicated medium format scanners can be quite expensive, and a good flatbed will deliver high-resolution scans from larger format film. Photo copyright George Schaub.

In addition, access to lab facilities that handle reproduction of film on prints is becoming increasingly difficult, and, when available, quite expensive. That’s why scanning, converting film materials to digital files, makes sense in terms of both “saving” those images as well as being able to do something with them, be it making prints or sharing on the web or even making photo books to pass on to future generations.

Project Outline

The project begins with a discussion on editing, and while, this is a personal affair, I will offer some guidelines on the process and encourage creating groupings that will help you focus on a particular body of work (and film type) which I found helped in not being overwhelmed by the task. I’ll also discuss what may make an image a “lost cause.”

I’ll then briefly cover the mechanics of a scanner, including certain criteria to use when obtaining the best scanner for your type and scope of work. There are various types of scanners available, and while budgets are one criteria (and again, this project is aimed at the enthusiast or at those individuals and institutions with “small” collections) using a poor or low-quality, limited option scanner is simply a waste of time.

I’ll then outline what you might call a “philosophy” of scanning, an approach that I find yields the best results, and then get into the main body of this project: scanner workflow. This includes step-by-step procedures for negatives, transparencies, and prints. I’ll explore matters such as calibration, resolution, profiling, dust removal, sharpening, contrast, color balance and more.

The only things I can talk about are my own experiences with scanning and what I have learned through that experience. Like me, you will find that a certain degree of trial and error is necessary, including modifying (or hopefully exceeding) your expectations and procedures, depending on the scanner and software you own and the shape your film and prints are in.

Scan from a 35mm black and white negative shot at the New Orleans World's Fair in 1984 made with a dedicated film scanner. Copyright George Schaub.

My hope is that this project will encourage you to respect your work by using scanned images to share and continue to manifest your vision for others to see. I feel it is important to preserve and enhance your images as well as those images made by those in the past.

One note: It is unfortunate that scanning older photographic material is necessary at all. But as we have learned, photographic materials are transient and subject to decay, be it density loss, color shifting or the deterioration of the image due to poor processing procedures. The paper base of prints, poor storage materials and the film emulsion itself can be at fault and cause not only the loss of image quality but of the very image itself. Scanning stops that progressive loss at the moment you perform the scan.

Next posting: The Edit

The Scanning Project

1) Introduction

The aim of this continuing series is to describe my experiences and hopefully encourage you to start your own scanning project. I will cover topics such as editing for scanning, working with various film types and formats, using flatbed and “dedicated” film scanners, and different software programs. I welcome your comments and suggestions.

This project is not aimed at archivists at large institutions who have access to very high end scanning systems, but is more suited to those with medium-size image collections who want to digitize their film work within a budget and with equipment that does not require an advanced degree to operate. It is also aimed at those who remain dedicated to film capture but want to output on inkjet printers or for web albums. The procedures discussed are also useful for small museums, historical societies and collectors who have  negatives, prints and even glass plates and want to preserve and perhaps enhance those images.

Like many folks who made photos during the film days, I disassembled my darkroom years back. I contributed the equipment to schools that still teach the chemical craft. 

Yet, I still had boxes and sleeves with transparencies and black and white negatives and slides of various formats that might not ever see the light of a print again—were it not for the ability to scan and digitize the images for web publishing and inkjet printing.

This scan from a 5x7 glass plate negative purchased at a flea market was made on a flatbed scanner using the “negative” scan mode, which converted it to a positive image, which was then processed to enhance contrast and clean up flaws in the emulsion. Photographer: Unknown.

Somehow I felt I owed it to the work done and time spent and visions captured to at least make the effort to transfer them to a medium that allowed me to both re-explore the work and manifest it in some fashion. While my main medium during those film days was black and white negatives, I also had lots of slides in both 35mm and medium format, and a scattering of color negatives and some chromogenic film (film that could be processed in color chemistry yet that lacked color dye layers so it was essentially a black-and-white medium.)

As I considered this task it became clear to me that this was not something I could do in a week or even a year. I have been photographing for almost 40 years and amassed a large collection of images. I had thankfully done culling throughout those years, yet I was still confronted by thousands of images in different formats and film types. The ones I kept were for sentimental reasons, because I thought they were good images that defined my vision and photographic quests, and simply because I just couldn’t make up my mind whether to keep or chuck them on my edit go-rounds.

That’s when the importance of editing became apparent to me, and while this is personal to each and every photographer it is an essential part of the process. (I can only imagine what future photographers will face when confronted in the future with the horde of digital images they have made.) I was never shy about using film and shooting a brick of film (20 rolls) on various stock and assignment jaunts, but digital encourages overshooting, what with the erase-ability of memory cards and high framing rates and super-automation that makes it all a pushbutton affair.

Luckily, in my past position as editor of various photo magazines, I had access to and tested numerous types of scanners and software along the way. During that period I would spend an intense week or more with each type of scanner and software and learn their capabilities and foibles to write my reviews and articles. But I never quite had the time to take on the “big project” of addressing all my past images, although the lessons learned during that time served as a good basis for the task at hand.

Next posting: An Outline of the Project