Digital cameras can be used to create high quality scans of film or print originals with rapid throughput at a reasonable cost, provided that a good digital camera is available. This page outlines the considerations for setting up and operating a camera scanning system.
With some special hardware, along with some proper techniques, it's possible to make excellent digitizations of film and print originals using a digital camera. The camera's sensor provides excellent resolution for the scan, even in comparison to dedicated film scanners such as Imacon. A DSLR's built-in anti-moire filter also helps in minimizing the appearence of dust and minor scratches present on the media being scanned.
You can compare the relative quality of a file made with an Imacon film scanner and a file made with a Canon 1Ds MkII. We have provided scanned image files for download here.
Camera scanning falls into two basic categories: digitizing film and digitizing prints.
Prints are a more straightforward process than film scans, since they are typically larger, and the scan needs only to reproduce the reflected color and tone. Often, good scans of prints can be made without any specialized equipment at all. A standard lens is generally all that is required, and lighting can be provided by conventional fixtures. In most cases, the scan produced by a digital camera will equal or exceed that made by a dedicated flatbed scanner, and can be produced in significantly less time. In addition, laying a print on a copy stand is potentially less destructive than laying it on a scanner, due to the lack of pressure applied.
When copying prints, it's generally best to use the highest resolution camera that you have available, depending on your intended use of the images. If images will only be used for web, significantly less resolution is needed than if the images are intended to be used for print.
Figure 1 A copy stand can help to speed the work of rephotographing prints. The lights should come in evenly from both sides at a 45-degree angle.
A copy stand (Figure 1) is a helpful tool for creating copies of prints, since it holds the camera still and parallel to the print. The stand helps to produce a sharp capture and with proper focus and "squared-up" corners. (Figure 2 shows squared and trapezoid representations.) While a tripod may be used instead of a copy stand, it is often less ideal for several reasons. Because the support column on a copy stand is mounted perpendicular to the base, it's easier to get the camera parallel to the print. Additionally, a copy stand typically offers unobstructed vertical travel for the camera, while a tripod typically has a more limited range of vertical adjustment without also readjusting the legs. Finally, the tripod legs can cast unwanted shadows on the print.
Figure 2 You'll want to make sure to get the camera parallel to the print surface so that the image reproduces without foreshortening, as seen on the left. While this can be fixed in Photoshop, it's much better to shoot it straight-on, if possible.
Lighting for copy work is most often provided by a pair of lights on either side of the print, set at a 45-degree angle of incidence, as shown in Figure 1 above. This offers minimal reflection from the print's surface, as well as side-to-side evenness. Sometimes polarizing filters are used on the lighting, in conjunction with a polarizing filter on the camera lens in order to reduce reflection caused by texture in the print's surface.
The color of the light source is also important, particularly for reproduction of color images. While digital cameras can be adjusted to compensate for the very red light of tungsten bulbs, or for the blue light of open shade, the camera can do a better job of creating a good color reproduction if the light source is a traditional "Daylight" balance. This is also referred to as 5500 degrees Kelvin. This color light can be provided most economically by using daylight-balanced compact fluorescent tubes, such as the Cool Flo. Strobes can also be used to achieve a daylight balance.
Figure 3 Daylight-balanced compact fluorescent lights can be used in a lightbox to provide a cost-effective light source for copy work of prints or film originals.
Shooting a target
For maximum accuracy in print copying, it's best to create a custom white balance for the camera. If you are shooting raw, and if the software you use supports a custom profile, you may find using a custom profile helpful. This can compensate for the imperfections of your particular camera, and can streamline the process of image optimization.
Creating camera scans from film is a more involved process than print copying, but the payoff can be even greater once the system has been configured. The result is a first-generation copy that will generally include more information than a copy of a print. And since film libraries contain many originals of the same size, it's possible to scan many thousands of images without having to readjust for size.
A camera scan setup for film will have five elements: the camera, a close-up lens, a film stage, something to connect the film stage and the camera, and a light source. Let's look at these elements.
Figure 4 Several of the systems shown below (lens-mounted, bellows and rail) can use a daylight-balanced source on a softbox to provide illumination for the film copying.
There are five basic types of film scanning system. The video in Figure 5 discusses the considerations of each of these.
Figure 5 This video introduces each type of camera scanning system, and discusses some of the characteristics of each.
A bench system, such as the Bessler Dual Mode Slide duplicator, is a self-contained system with a light source, a film stage, a camera mount and lens bellows in a single system. As of this writing, there are no bench systems that are currently being manufactured, although there are many used systems available on the resale market. Bench systems are reasonably easy to configure as a do-it-yourself project.
Other options for bench systems include the Kenro Spectra 1000 and the Omega ChromaPro slide duplication. The popular Bowens Illumitran unit generally does not fit a digital camera body.
Figure 6 A bench system
A lens-mounted system connects the film stage to the closeup lens itself. There are several commercial lens-mounted systems that are currently in production, but they suffer from a number of drawbacks. They tend to put a lot of stress on the moving parts in a camera lens, which can lead to failure of the lens. Additionally, they are typically not rigidly supported, so that the negative is not in the same exact location in each shot, which leads to a more difficult cropping of a multiple images.
Figure 7 A lens-mounted system
Bellows systems have been in use for decades as slide copiers. Typically, there are three movable elements: one for the camera and one for the lens that are connected by a bellows, as well as a film stage that is attached to the same rail. Note that bellows systems will only work for some camera and lens combinations. Crop factor cameras change the lens-to-camera distance, and can prevent the camera from focusing at the proper distance. A good daylight-balanced light source needs to be used to provide illumination. A bellows system offers good workflow and ergonomic freedom, since it can be tripod- or stand-mounted for comfort.
Figure 8 A bellows system
Rail systems are similar to bellows systems, but use a macro lens directly attached to the camera instead of the bellows. A film stage is also mounted on the end of the rail, and some kind of daylight light source must be used, just as with the bellows systems. Rail systems typically offer faster workflow than bellows systems because the macro lens provides for full-aperture viewing and automatic stop-down, while most bellows systems require manual aperture opening and closing. Rail systems are also much more flexible and support more camera and lens combinations.
Figure 9 A rail system
Copy stand systems
A copy stand and light table system is the do-it-yourself version of the bench system, as pictured in Figure 4. A film holder from an enlarger can be used with a lightbox or other backlight to provide the film stage and lighting. Note that critical focus and image squareness requires the camera to be exactly parallel to the film surface. This is harder to achieve as the film gets smaller, so these systems may be best suited to medium and large format film originals.
You can use your raw file processing software to optimize your camera scans. If you are scanning transparencies, nearly any raw file processor will work. If you are scanning negatives, the software must have the capacity to invert the image, usually by means of a point curve. Figure 10 shows the new point curve in Lightroom 3 that offers the ability to invert the brightness.
Figure 10 In order to turn a positive to a negative, it's essential to flip the curve upside-down. Adobe Camera Raw can do this in all versions, and Lightroom can do this as of version 3.
Slides are the most straightforward camera scan images to process, since the tools in raw file conversion software are built to work with this color and tonal range. One of the most common needs in working with color slides is to open the shadow areas of the image, since these often pick up additional contrast in any reproduction process. The Fill Light command in Lightroom and Shadow control in Aperture can do a good job with this task. It's often possible to make very good versions of your images quickly, without needing to make a derivative and work in Photoshop. Figure 11 shows how the tools in Adobe Lightroom can be used to optimize camera scans of slides.
Figure 11 This video demonstrates how to use the controls in Adobe Lightroom 3 to adjust color transparencies that have been rephotographed with a digital camera.
It's possible to make excellent positive images from camera-scanned black-and-white negatives.The image must first be turned positive, which can often be done with a single setting for an entire roll. If the exposures on the film have too much variation for a single adjustment, individual images can be further adjusted on a rapid basis.
The non-destructive nature of parametric image editing allows for quick proofing of a large group of images, without prohibiting readjustment at a later date. This allows the imager the ability to proof quickly, and create optimized images once a need for a higher quality version arises. In many cases this will be the optimum workflow – shoot and proof quickly, and optimize as higher-value needs present themselves. The videos in Figures 12 and 13 outline both of these procedures – quick proofing for an entire roll, and careful toning of a single image.
Figure 12 In this video, an entire roll of black-and-white negative film is turned to positive and given a basic adjustment. Individual images are then tweaked for their particular needs.
Figure 13 In this video, a single image is reworked to make a more finished copy of the image, suitable for high-quality reproduction.
Color negatives are the hardest film images to camera scan due to the difficulty of transforming the color in the negative to a positive. It's possible with a little work, however, to make a good conversion. There are a few steps.
Neutralizing your light source
The light source for the copy should be filtered to remove the orange cast of the film base. This puts the color within the range that a digital camera is optimized for. This may be most easily done by using color compensation (CC) filters on the film stage. If you are using a bench system described above, you can probably dial in the proper filtration. Here's one methodology for making sure you filter out the film base.
- Set the camera to daylight or strobe white balance.
- Shoot a test bracket with the film type you are copying.
- Bring the image into your raw conversion software. Make sure that the software is set to honor the camera setting for color balance (the "as shot" setting).
- Read the white balance in an area with no color cast, such as the clear film base, or some object that you know is neutral in color.
- When the light source is filtered properly, this readout should have equal values for red, green and blue, without making any changes to the white balance in the software. If the readings are not equal for RGB, try a new filter pack until you get a neutral reading.
- It's not necessary that the reading be perfectly equal for the colors, since you'll be doing some further color manipulation anyway.
The video in Figure 14 outlines an approach to processing the color negative scan. Just as with the black-and-white, the image is turned into a positive by flipping the tone curve upside down. Once that has been done, you can use color controls to adjust the color. Again, the controls will work in reverse if you are using software that is meant for conventional digital camera files. This makes the process much more difficult than working with black-and-white, since the color will now work in reverse as well.
It's possible to take camera scans of color negatives into dedicated scanner software, such as Silverfast. While this may not present a fast or convenient workflow, it will allow the use of custom color curves that have been built for different film types.
Figure 14 This video outlines the process for creating camera scans from color negatives in Lightroom, and shows how a DNG that has been adjusted in Lightroom can be opened in Silverfast.
Camera scans white paper
This white paper was prepared for the Imaging Science and Technology's Archiving 2009 conference. It outlines the issues involved in camera scanning from the perspective of a cultural heritage institution as well as an individual photographer.
You can download the white paper here.