Although digital cameras are the most popular devices used to capture photos, scanners are still widely used to scan slides, negatives, and prints. You can do this yourself if you have a scanner, or you can have them scanned onto a CD disc or floppy at your local photofinisher or lab. The resolution of some of these scans is often equal to or even higher than you get from all but the most expensive cameras, so if quality is an issue this may be a possible route to take.

Photo Transfer (Bulk Scanning) Services

When you convert to digital photography you leave behind years, or even decades, of prints and slides that lie in drawers and boxes. None of these photos are in your digital workflow so they can't be organized and used the way your digital photos can be. You can buy or borrow a scanner and scan them into a digital format, but you'll soon find that very time consuming. A better solution is to send them all to a service that will scan them for you and return them along with a CD/DVD. You can have this done at expensive professional labs, but there are many low-cost services that use high speed auto-feed scanners and low, but useful resolutions, to keep down the costs. At the time this is being written one site was scanning 1000 prints for $50—5 cents per image. One of the first things to check is what resolutions are used when scanning. Some services give you a choice, with higher resolutions costing more.

• Slides scanned at 2000 pixels per inch give you 3000 x 2000, or 6 megapixel images. The scanning resolution is so high because slides are only 1.5 x 1 inches.
• Prints scanned at 600 pixels per inch yield 2400 x 3600 or almost 9 megapixel images from 4 x 6 inch prints. At 300 ppi images are 1200 x 1800 or a little over 2 megapixels.

Since you can get high-quality inkjet prints using 200 pixels per inch you should be able to make sharp prints of the same or even larger sizes from any of these digital files.

Auto-feed scanners cannot scan color Polaroid prints or photos mounted on cardboard so you will have to pay higher rates for those scans. However, the scanners will handle index cards and this can be useful. When you get your images back, they are all identified by numbers. If you want them organized into categories, you can insert annotated index cards into the stack of images you send. These cards will then be scanned along with the stack of prints they subdivide. When you look at the disc's contents later, these cards appear as thumbnails along with the images, giving you an idea of where each category begins and ends. Some services also offer printed albums or proofs showing thumbnail images of the scanned prints. These make a great index to the contents of a CD/DVD.

One thing to check for when having slides and negatives scanned is whether the service uses scanners equipped with software called Digital ICE from a company called Applied Science Fiction (http://www.asf.com). This software automatically identifies and removes surface defects, such as dust and scratches, from a scanned image, sometimes improving upon the original image. The latest versions not only remove surface defects, but also restores and corrects color, reduces film grain noise, and optimizes contrast and exposure.

When it comes to sending your photos off for scanning, it's nice to know you are dealing with a quality company. The first time you try a service, you may want to send them a small group of photos the first time to see how the order is handled and the quality of the images you receive. Even in you like their work, you may want to break your job into parts so all of your photos are not at risk at the same time. Even large, brand-name firms such as Wal-Mart and Kodak make mistakes and can loose your images.

Kodak's Qualex subsidiary offers a picture scanning service to on-line and retail customers. You can either pick up a kit from a participating retail location or order a kit from an on-line web site. You then follow the instructions to package your photos either return the kit with their prints to the retailer, or ship it directly to Qualex. Qualex scans the images, uploads them to an online account and stores up to 2000 of them on Kodak's Picture Movie DVDs. The original pictures and DVD are returned in the same manner they were delivered to Qualex.

If you don't want to send you photos off into the unknown, you can scan them right in some stores. Kodak's s1220 Photo Scanning System lets you feed multiple prints for batch scanning, and associated software to capture the photos and perform simple enhancements such as sharpening, removing red-eye and restoration. The scanner scans up to 30 pictures-per-minute and the images can be stored on a CD/DVD or uploaded to on-line photosharing sites.

Scanning Basics

Color scanners work, as cameras do, by creating separate red, green, and blue versions of the image, and then merging them together to create the final digital image. Some scan all of the colors in one pass while others take three passes, a slower but higher quality method. Which method is used depends on the scanner's image sensor. Most scanners use linear CCDs arranged in a row. Those that require three passes use a single row of photosites and pass different filters (red, green, or blue) in front of the sensor for each pass or use three different light sources. Other scanners use 3 rows of photo sites, each row with its own filter so they can capture all three colors on a single pass.

As the image is scanned, a light source travels down the photo (some print and document scanners instead move the document past the light source). The light source reflects off a print or passes through a transparency and is focused onto the image sensor by a mirror and lens system. Because of this mirror and lens system, the sensor does not have to be as wide as the area being scanned.

The horizontal optical resolution of the scanner is determined by the number of photosites on its sensor. However, the vertical resolution is determined by the distance the paper or light source advances between scans. For example, a scanner with a resolution of 600 x 1200 has 600 photosites on its sensor and moves 1/1200 of an inch between each scan.

• Some scanners are designed to scan photos and other documents, called reflective copy. Others are designed to scan slides and larger transparencies.
• Reflective scanners can scan 8� by 11 originals but some can go much larger. Transparency scanners scan 35mm slides and negatives and some will scan even larger photos. As the size increases, so does the cost.

Color or Bit Depth

Just as cameras capture JPEG and RAW images using a different number of bits per color ( 8 or 16) so do scanners. At the moment, most affordable units capture 14 or 16 bits per color—4² or 4⁸ bits total.

Resolution

The true resolution of the scanned image depends on more than the scanner's resolution. It's ability to capture details is known as its resolving power. This resolving power is determined not just by resolution but also by the quality and alignment of it's lenses, mirrors, and other optical elements and the accuracy with which it moves along the image when scanning. It's possible for a very well designed scanner with a lower resolution to outperform a cheaper one with a higher resolution.

As with other digital imaging devices, be sure to look at the hardware resolution, not the interpolated resolution. The differences can be dramatic. For example one scanner lists a hardware resolution of 800 x 1600 dpi and an interpolated resolution of 9600 x 9600 dpi.

Dynamic Range

Scenes in the real world are full of bright light and deep shadows. The extremes are referred to as the dynamic range (called tonal range while editing). Film doesn't have anywhere near the dynamic range of nature, so when a scene is captured on film, the image doesn't usually capture the entire dynamic range or all of the details. When the film is then used to make a print, more of the dynamic range and more of the details are lost. This is one of the reasons that it's better to scan slides or negatives then prints. Monitors have a dynamic range closer to slides than to prints. This means that when you scan images for the Web, you need to be sure you capture as much of the dynamic range as possible.

How much dynamic range you can capture depends on the scanner's ability to register tonal values ranging from pure white to pure black and separate out tones at the extreme ends of the range. If the scanner doesn't have enough dynamic range, details are lost in shadow areas, highlights, or both.

A scanner's dynamic range is measured by the manufacturer and expressed as a numeric value between 0.0 (white) to 4.0 (black) that indicates its ability to capture all values within the full dynamic range. Common flatbed scanners typically register values from about 0.0 to 2.4. Newer 42-bit scanners claim a dynamic range up to around 3.4, making them more adept at pulling detail out of shadow areas within images.

Although image density ranges from pure white to pure black, no detail can be seen in those areas. As you progress from pure white into slightly darker areas, detail emerges. The point at which a scanner can detect this detail is called DMin (minimum density). The same is true at the other end of the spectrum. The point at which detail can be detected before the image goes to pure black is called DMax (maximum density). The dynamic range is calculated by subtracting DMin from DMax. For example, if a scanner has a DMin of 0.2 and a DMax of 3.2, its dynamic range is 3.0.

Film Scanners

To scan slides or negatives you need access to a film scanner (sometimes called slide or transparency scanner). By using the included filmstrip holder, negative strips up to 6 frames in length can be scanned, one frame at a time.

Because slides and negatives are so small and must be enlarged so much, these units must have very high resolutions to be really useful. A scanner that scans 4000 dpi, creates files from slides and negatives that are 6000 x4000—24 megapixels.

If all plan on scanning mostly prints and some negatives, look into flatbed scanners with transparency adapters and film holders for negatives and slides. Some of the best film scanners use Digital ICE from Applied Science Fiction to eliminate dust and scratches on the surface of the scanned film.

Flatbed Scanners

Flatbed scanners are reflective scanners useful for scanning both black and white and color prints. Flatbeds are excellent for scanning old photographs for restoration purposes. (The print should be removed from any frame to make flat contact with the scanner glass. Make sure the glass on the flatbed is clean.)

One advantage of flatbed scanners is that they do double and sometime triple duty. In addition to copying prints, some can also scan slides and negatives, and many also come with OCR (optical character recognition) software that converts printed text to an editable digital form.

There are two primary image-capturing sensors used in flatbed and sheet fed scanners: the Charge Coupled Device (CCD) and the Contact Image Sensor (CIS). Since scanners using a CCD required an elaborate lens and mirror optical system, there is lots that can go wrong if things get out of alignment. To simplify the system, and lower its costs, new CIS (contact image sensor) scanners use a single row of sensors that are in contact with the document being scanned. The document is illuminated by a row of red, blue, and green LEDs. Various proportions of these colors reflect to create mixed colors that are then captured. This design makes it possible to have very thin scanners but the image quality does not yet match CCD scanners.

When first encountering a copy machine, many people have tried copying money, photographs, and other objects. Some even go so far as to press their nose or other parts of their anatomy against the glass to capture an image.Basically, they are using the copier as a lensless camera. You can do the same with a flatbed scanner and the results can be interesting. One trick is to try different background materials laid on top of the objects to be scanned. These can range from another image to black velvet.

Many flatbed scanners come with a transparency adapter so you can scan slides and negatives. The adapter replaces the standard copyboard cover and diffuses light evenly through the transparent media. Generally, the resolution of these units is below those of units designed to scan transparencies.

Drum Scanners

When price is no object and quality is paramount, you need to have prints or transparencies scanned on a drum scanner. On these scanners the transparency or print is affixed to a glass drum. As the drum spins, the image is read a line at a time by a photomultiplier tube instead of a CCD. A bright pinpoint of light is focused on the image and its reflection (prints) or transmission (transparencies) is measured by the tube. These tubes provide the highest quality RGB and CMYK scans with greatly improved highlight and shadow detail. Their dynamic range is so high they can capture detail in both deep shadows and bright highlights and they also capture subtle differences in shading. Resolutions range up to 12,500 dpi and higher and these scanners have very large scanning areas. Drum scanners use liquid mounts to mask surface imperfections such as scratches. The liquid also minimizes rainbow colored Newton rings that form when film is placed against a polished drum.

These expensive scanners are available at service bureaus where you pay by the scan. The cost of the scanner, computer time, and labor involved with a drum scan demands a higher charge.