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-5: Editing Color Negative Film

There were literally hundreds of types of color negative film, with various speeds, brands and emulsion stocks on offer. When these were mass printed in photofinishing labs, the equipment processing and printing the film identified those various stocks by their edge coding and made automatic color balance decisions accordingly. Sometimes this worked well and sometimes it didn't. 

But knowing the brand and type of color negative film you are scanning can be quite useful. You might be able to read the brand of film on the perforated strip. (See Posting 4 for a link to a site that ID’s numerous Kodak films by their codes. You can also Google a particular film or type. For example, googling Kodacolor--Kodak color negative film--will yield the years of manufacture and film codes, which can be helpful.) This information is used when applying film profiles to the scan and different profiles can be profoundly different in terms of color balance and contrast. However, knowing exactly which “vintage” (emulsion stock number) of film you are scanning is near impossible and there were variations (though they can be slight) depending on which emulsion stock number the film might have been.

This color negative film, scanned as a positive to show the orange mask, is not an easy "read" in terms of color, since both color and density are reversed and sit within an amber layer.

Here's an image of what the negative would look like when the amber layer is removed. By studying the positive (below) you can see how "reversed" colors (actually the complement to the positive colors) look. This takes some practice, although the easiest way to figure this out is to simply scan the negative, as a scanner will remove the orange mask effect in the process.

Here's the positive made from the scan. This exposure was made on Kodak VR 200, a film sold starting in 1984 and discontinued about 1986. The perf code on the film is CL, which when cross-referenced on Wikipedia led me to the film brand and type, which I used as the profile when scanning. 

While batching the types for scanning sets by film type in your initial edits is a good beginning, it is likely that you will have to fine tune the color balance yourself during scanning, which is not a difficult task, though it can be time consuming.

One problem of course is being able to see through the color mask that was incorporated in virtually all color negative film. This orange/amber coating was incorporated to enhance color reproduction, but also makes “reading” color negatives tougher than slides or black and white. Being a negative, the colors are “reversed", if you will, to their complements when the image is printed (color slide film is processed so the reversal takes place during processing via chemical or light exposure). All in all, the only way to see what colors you have (unless you have a very trained eye) is to scan the negative itself, which will eliminate the mask and make the colors positive.

When high speed films came out in the mid eighties they gave a newfound freedom to low light shooting. They did have their problems, however, as most were daylight balanced, many were quite grainy and contrasty, and I have found that the years have not been kind to their stability. This photo inside a Chicago blues club was shot in 1985 using Kodacolor VR 1000.

This is a scan from the print I got back from the lab at the time. Being daylight balanced, the film recorded an overall amber cast. I am unsure if the lab attempted to rebalance the light but I accepted it as the final output of the image at the time.  It was enough to be able to shoot in such low light without flash. 

When I scanned the negative I had to rebalance the color myself as there was no matching profile provided in the software for VR 1000. Knowing that the image was heavily influenced by artificial light I added blue and cyan and played a bit with the contrast. My aim was to produce an image that looked like it was shot with tungsten balanced film. 

However, color reversal and the orange mask are not the only issues with color negative film. In my experience, color negative films of older vintage suffer from density loss, color shifts (some are worse than others) and emulsion deterioration. There are three main color layers (CMY—cyan, magenta, yellow) within the emulsion itself, with some layers usually suffering more than others. Frankly, manufacturers did not do a good job insuring that color negatives would be “memories that live forever”, as the advertising claimed.

Of course, how you stored those negatives is also an issue, and if you stored them in shoeboxes you will probably have dirt and scratch issues to contend with as well. Not to worry, however, as color negative films can be put through dirt and scratch removal software algorithms, which will help. You can also manually clean the film by rewashing and immersing the film in PhotoFlo, or passing the film very carefully through a chamois cloth.

One option is to remove the worry about color by converting problem or poor color negatives to black and white. While this should be a last resort, it can help maintain the image if not the original color itself. Doing so you can deal with contrast and density issues and not worry about color balance.

Most software will offer a color profile of many types of commonly used color negative film. While these should be considered ballpark algorithms, they are a good place to start; in my experience you will certainly spend more time balancing color negatives film than you will when working with color slides.

So, batch the negatives as best you can according to film type and brand, check each frame with an 8X loupe and be prepared to hunt and peck to find the right color balance. We’ll cover profiling in the coming post on color negative step-by-step scanning.

My guess is that the vast majority of color negative films were shot with affordable cameras and in many cases the negatives are lost or simply tossed as being thought unnecessary. These photos are often the storehouse of precious family memories and should be scanned to protect and preserve them for future generations. I am always amazed at finding family photos in the form of black and white prints from over a hundred years ago that are still in very good shape, but mass produced color prints from only thirty to forty years ago that quite clearly are not. Scanning color prints (those with or without negatives) using a flatbed scanner is an easy matter. This print is from the 1970s and had already shifted color towards a magenta cast, alleviated somewhat by changing the color bias when scanning. 

Unfortunately, many people who shot color negative film of family and travel memories usually used other than stellar cameras and lenses. The plastic or hybrid lenses used in these cameras were notoriously soft and more than not automatic exposure modes, or guesswork, was used when shooting.

When scanning such images, expectations should be kept in check, although getting good scans for web sharing sites and even photo books—if image size is kept “reasonable”—allows these memories to be preserved. Frankly, in some cases scanning from the original snapshot print, if it’s not too far gone, may be a better strategy for such uses.

The Scanning Project-3: Editing: Color Slides

While you might think the first thing to do is run out and buy a good scanner (I’ll go over different types of scanners and their benefits in a future posting) the most time-consuming and crucial part of the process is figuring out what you want to scan.

There's no question that some types of slide film hold their color and density better than others. This scanned Kodachrome, shot in 1992, still retains all the tone and color from the day it was processed. Photo copyright George Schaub

 The benefit of starting with past work is that you have had time to “digest” whether that work still holds meaning for you. This helps in the editing process as hopefully you have become more discerning in terms of image quality as well as considerations of what image content stands the test of time. In some cases, for those who shot film way back, the physical condition of certain types of film will play a big role in this process.

As to what images to choose that is a very personal matter and I will not make any suggestions here. All I can say is that if you have dupes or similars of a particular shot do take some time to pick the best of the lot. This might seem like it goes without saying, but editing means making choices, and getting involved with scanning means that you will be making decisions about picking the best of perhaps four or five shots of a particular scene. Just plant your flag and go for it!

Color Slides

The first step is to think about, and choose, slides that will yield good scans. As you work you will learn what might work, what will require extra effort to get right, and what slides are just not going to turn out right. You can fight city hall to an extent, thanks to software, but there are simply some slides that will not work out. You can try a few poor quality slides to see how far you can take them, especially if they are of precious moments or memories, but don’t expect much from them except having a record and a snapshot of them in their current condition.

Here's a scanned Ektachrome exposed and processed in 1994. The original was color rich and had textural whites, even in the bright clouds in the sky. While there is certainly some diminution of the color, the biggest problem, and that which will dash any hopes of getting a good print from the full frame, is the loss of density in the brighter areas of the clouds. Note the burnout of the cloud edge above the beer mug. This cannot be properly burned in and although very experienced software users might be able to get some texture back, overall it might just not be worth the time required to get it right. Photo copyright George Schaub

Of course, one option is to crop out the offending area. That's what I did here, but by doing so I got pretty much right to the edge of acceptable sharpness, and would opt to make this a considerably smaller print than I might otherwise like. I also cloned some of the blue into the upper right edge to get rid of some burned out sky. Knowing what you can and cannot accomplish and making edits accordingly will save you time and perhaps wasted efforts later.

One of the worst kept secrets in photography is the poor keeping qualities of certain types of slide film. A good read is Henry Wilhelm’s “The Permanence and Care of Color Photographs” (http://www.wilhelm-research.com) in which he rightfully chastises certain manufacturers for the poor keeping qualities of products that promised to be “the memory keepers.”

Even with optimal storage conditions, many types of transparency film will, by their very nature, begin to deteriorate way before one would anticipate, or hope. If you have not looked at your old slides of a certain breed for many years you might be shocked at what you discover—color shifts (mainly towards magenta), surface deterioration and density loss (blacks becoming mottled, whites and highlights blanking out). This is nothing new. Commercial photographers found this out many years ago when trying to salvage their E-3 processed Ektachromes.

Luckily, some of this loss can be ameliorated by software, but when highlights are gone in positive film there’s no bringing them back. In my experience this is a common occurrence with most slide films of a certain vintage, although Kodachromes, due to their unique construction and processing, do best in this regard. Other Kodak produced films turned out to be real dogs, including higher speed Ektachromes and especially older Ektachromes, even those with E-6 processing. Labels like Anscochrome and Agfachrome can be abysmal in their keeping qualities.

Here's an Agfachrome exposed and processed in 1990. The shift to magenta is apparent, and there has been considerable density loss. In most instances, scanning and trying to get something decent out of such slides might be a waste of time, although I certainly do not discourage your trying: that's how you'll learn about what should be edited in and out of your scan collection. Copyright George Schaub

One option of course is converting to black and white, which in one step removes the curse of the color shift and allows you more control over density and tonality. This is a good strategy for precious photos of family and friends.

 The proper storage for older film materials is not in the realm of this discussion, and again Wilhelm is a prime source on this matter, but common sense methods include storage in low humidity and low heat conditions, using so-called archival storage materials, and limiting exposure to light. (One interesting sidebar is that while Kodachromes generally stood the test of time much better than other materials, if you regularly projected Kodachromes you have substantially cut down on their life expectancy. That’s why slide trays of experienced presenters contained not original Kodachromes but dupes.)

Note the retained textural whites in the flag bunting in this scanned Kodachrome from 1984. Slides like this are easy to scan and yield excellent prints. When you edit, batch images with these characteristics for a productive and rewarding scanning session. Start with these so you can get some positive reinforcement about what scanning can do. Likewise, batch the problem slides and those with similar flaws together so you can develop a workflow plan that will aid in their recovery.

Photo copyright George Schaub

In any case, one of the first considerations of editing might be to choose and salvage as best you can those slides that are starting to go over the edge. They will be apparent to you as you edit your materials. Keep in mind that some may be irredeemable, but if the image is important to you, such as childhood photos of your now grown children, also keep in mind that you can always ignore the color shifts by converting the image to black and white or even rescue some of the “natural” color via processing. As to density loss (highlights gone blank) there’s nothing much you can do about that, although judicious cropping and some software work can help salvage something from your most precious shots.

Finally, batch your edits by film type as best you can, as you may be working with film “profiles” with certain types of scanner software as a way to get a ballpark read on the proper values for each type of material. This is especially true when scanning Kodachromes versus other types of slide films. In general, Kodachromes are usually “warmer” than other types, and their color layers are quite distinct in character. This segregation by type might be difficult if you have generic (non-brand labeled) mounts, but do the best you can.

Next posting: Editing, Black and White