The Scanning Project-8: Scanner Terms and Important Specs

 There is no sense buying a scanner or making scans on a scanner that does not have the right tools for the work you intend to do. In this post I will cover the main specs to check and what I consider important benchmarks for a variety of projects you may have in mind. As an introduction to the terms, following is a brief description of each and why they are key elements in determining image quality. These will be covered more extensively within the context of the scanner workflow discussions in following posts.

Resolution: In essence, resolution is a prime determinant of how large you can create a print from the scanned image. Much like the megapixels in a digital camera, the larger the file produced the larger the potential enlarge-ability. Of course, other matters come into play, including the quality of the scanner lens and sensor, but given all other things are equal (which is rare) the higher the resolution you choose the bigger the file produced, thus the greater degree of enlargement.

Scanner resolution is expressed as pixels (or dots) per inch. The important thing to watch for is that the resolution is expressed as Optical Resolution. Some scanners are misleadingly labeled as having high resolution when actually what is being stated is the potential interpolated, or resampled resolution capability. This means the image is crunched, if you will, to extrapolate a higher resolution than the actual optical resolution.

This is an image size dialog box from a scanner 35mm slide that was cropped slightly in scanning. The scan was made at 3200 dpi. The dialog box on top shows the scan when it has been converted to printing resolution, resulting in an 11x16 image size. Note that this can be edged up a bit using resampling at this stage, a topic covered in the workflow sections in later posts. 

Simply put, the higher the optical resolution the larger the image file. When selecting a scanner make sure it has a minimum of 4800 dpi; 6400 dpi scanners are becoming more affordable and are a good choice if you work mostly from 35mm film. But keep in mind that when scanning at 6400 dpi every sharpness and other flaw in the original will become quite apparent, like looking at yourself in a magnifying mirror in the morning. In addition, scanning at 6400 dpi can result in some very large image files, perhaps beyond your needs. It also can point out flaws in the lens that you used to make the photo that might not be apparent even when viewing the film through an 8X loupe.

Here's a scan from a 6x7 medium format negative. Note the larger image print size that can be achieved. This scan was initially made at 3200 dpi.

Bit depth: Again, as with digital cameras, you can choose the bit depth of the image, which means how many bits of information are captured within the three color channels of the sensor. You often have a choice of bit depths, such as 8-, 24-, 36- and in some scanners 48-bit.

Think of the difference between 16-bit RAW file and 8-bit JPEG images made in your digital camera. The 16-bit file simply has more image information available, which means you get a lot more potential out of the scan. But just as with resolution, the higher the bit depth the larger the image file, so consider the tradeoffs. For the most part, 36-bit will do the job, and for some end uses 24-bit and even 8-bit (for black and white images for web) may do just fine.

Dynamic Range: This is one of the main scanner specs to check. Dynamic range is a term you might be familiar with in the context of your digital camera. At the camera’s lowest ISO settings that range might be 10-11 f-stops, meaning that tonal values within that span can be recorded; the dynamic range of any camera inevitably falls as you raise ISO. In scanners, the measure is not f-stops but in something called Optical Density and is within a scale of 0.0 (white) to 4.0 (black).

Watch for how the scanner’s specifications (read capabilities) are expressed in Optical Density terms. A scanner that’s Optical Density falls between 2.0 and 3.0 may work for some prints and “quick” tasks, but generally there will be a loss of highlight and deeper shadow information—in other words, it is quite flat. Scanners in the 3.2 to 4.0 range are more suitable for the kind of work you might be interested in, with the higher number offering a better dynamic range capability. In other words, the higher Optical Density rating will bring out the most tonal (thus color richness as well) qualities of the image.

Flatbed or Dedicated Film Scanner?

There are two main types of scanners for photographers and those working with photographic images. One is a flatbed that can handle most film formats (35mm up to 8x10) and prints up to the platen size, the most common being 8.5 x 11”. Flatbeds can also be used to scan tintypes, daguerreotypes and glass plate negatives. A flatbed can be versatile, but if you have only 35mmn prints and negatives a better choice would be a dedicated film format scanner, commonly for 35mm but also available for medium format (120) film. 120 film scanners can cover all the 120 formats, including 6x6, 6x9 and even 6x17 negatives and slides. (Larger format dedicated scanners are strictly for professionals and will not be covered in this project.) Note that flatbeds can usually do a good job with 120 format and a reasonable job with film as well. How well depends on the scanner’s specs and build.

Thus, the scanner you choose is highly dependent on the type of images you want to scan. If you are a family photographer with lots of old snapshots and prints and only a few boxes of 35mm film, go for the flatbed. If your collection is primarily composed of 35mm film then go with a dedicated film scanner.

Quick Guide: Scanner Specs for Film and Prints

Here is a quick rundown of the scanner specs I believe are best for your work. Of course, budget and the volume of work you plan to scan should guide you, but scanning via a low-spec scanner is generally a waste of your time.

Optical Resolution: 4800 dpi; better: 6400 dpi

Color Bit Depth: maximum, 48-bits per pixel, 36-bit is usually fine

Grayscale Bit Depth: 16-bits per pixel

Optical Density: 3.4 minimum; best: 4.0

Light Source: LED

Platen Size (for prints): 8x10”; better: 8.5x11”

Film Holders and Masks: Dependent upon your formats, 35mm to 4x5” film

Bundled Software: Covered in the next posting

Next posting: Scanner Software

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