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-6: The Print, and Some Final Thoughts on Editing

Many folks have prints without negatives, mainly family photos from generations past, but there are also collectors and museums who have tintypes, albumen prints and even daguerreotypes. The quality of these items varies considerably, often showing signs of age due to fading, paper support deterioration and glitches in the emulsion surface. Scanning paper and other materials that support images is a fairly straightforward affair, and getting like copies is not difficult. The challenge comes in when you go to revivify, if you will, the image, a task that has been made easier with software retouching.

I am always amazed at the quality of very old prints that have been toned, and even black and whites that have been stored even under non-archival conditions. This carte de visite (about 5x7") was probably made in 1880s or so and was found in great condition. I scanned it in color to retain the sepia tone color and then did some minor retouching in software. 

 In the days when film was used for print copies, which I did commercially for many years, I would make a 4x5 negative with a copy stand setup and hand the print off, if needed and after I did my contrast and dodge and burn thing in the darkroom, to an airbrush and retouch artist, who would use the tools of their craft to reconstruct torn and damaged areas.

The success the job was heavily dependent on the original print condition and what I could do in the darkroom, and at times the results were more interpretations than true to the original image. At times the person bringing the image in for work would supply what details they had, such as eye and hair color and skin tone, and the artist would hand color the print. While the final look was at times more sketch-like than photographic, it still kept a treasured memory alive for future generations to come.

There was a time when I did a lot of hand coloring, adding photo oils to black and white prints. While the negative of this image is still in my files the only way to copy this unique treatment was scanning the print itself. The print is 8x10" so there was no problem handling it in one pass on the flatbed scanner. Image copyright George Schaub

 While the discussions here are not aimed at professional digital retouchers, I will go over some ways that an image can be enhanced and salvaged that are available to all with basic image editing programs later in these postings.

Naturally a flatbed scanner is used for scanning prints. Most of these that are not pro units offer letter size (8.5x11”) as the maximum scanning size. You can scan sections and merge larger prints later. You can also scan numerous snapshot size prints in one pass, then crop from the full scan to make corrections later. Some scanners/software can even ID individual snaps for you and create a file for each separate print; either way works fine, as you will not be sacrificing resolution whether you batch or scan individually.

There isn’t much to say about edits, as you can, with most scanners, get a virtual copy of the color and contrast of the print, and the only batch sorting you might want to do is between color and black and white and by print size. 

This is not a mistake in the way I scanned this photo I found in an old album at a flea market. The print image had gone full tilt and was very close to disappearing altogether. I scanned it first "as is."

To bring it back to life so that I could actually see the individuals in this group shot I made a simple adjustment when scanning to enhance the contrast, something I could as easily have done later in image processing software. The point is to not become discouraged when you find a poor quality print, as there are many ways to enhance and improve the image. If need be an image like this could be handed off to a pro retoucher but for me this result is mission accomplished. 

 Some Final Thoughts on Editing

Each of us has our own editing “eye” and that is certainly a personal matter. However, I could suggest that you begin the scanning process by working with projects. For example, you might want to start sorting into sections such as family, nature, florals, artwork, etc. or whatever makes sense to you. This way you can learn as you go and not feel overwhelmed by having to edit everything in your film and print files all at once. Harvest images selectively rather than trying to edit a lot of work at once.

Editing is an ongoing process (and by editing I mean dividing work into keepers, and maybes and outs) that will take time. But keep in mind that it is the most time-consuming part of this whole process, as it should be. Once you do your edits you’ll find that scanning is quite mechanical (after you learn the workflow) and easy. Scanning is an important creative process, and editing is at its heart.

How many images should you decide upon before you first begin scanning? That’s up to you and just how many images there are in your collection. I suggest that you begin with about 100, including good and not so good quality images.

You can make this your test run to become familiar with the scanner, the software and the best workflow. By working with a select group you will begin to see what you can and cannot accomplish and how you can or cannot salvage marginal images, and this will in turn feed back into your editing procedures and decisions.

To sum up:

Scanning itself is a mechanical process; although you can be creative in certain choices you make it is often best to simply scan to gain all the information you can from the material and then interpret as you will later. Scanning involves a set of decisions and commands that will affect the outcome, and each step is quite clear in its implications.

Editing is a creative process, where you make decisions about what images are meaningful to you. Editing is an emotional and aesthetic process. It becomes refined as you work through your images, and in itself is a wonderful way to revisit images you may not have looked at for many years.

There’s art in the science and science in the art of scanning, just like in photography itself.

Next posting: How a Scanner Works