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Scanners - PhotoCourse

AA30470C

Scanning—Photographing Photos

Cover

An Extension to

The Textbook of Digital Photography

Scanners

Photographing Photos

AA30470C

D e n n i s P . C u r t i n

h t t p : / / w w w . ShortCourses. c o m

h t t p : / / w w w . P h o t o C o u r s e . c o m

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Scanning—Photographing Photos

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Scanning—Photographing Photos

Scanners—Photographing Photos

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.

Kodak’s family of

scanners.

Sites to Visit

• scanmyphotos.com

• britepix.com

• digitalmemoriesonline.net

• digmypics.com

• yesvideo.com

• scancafe.com

A proof book from

scanmyphotos.com.

Kodak’s s1220 Photo

Scanner.

The Kodak i660 scanner

will scan 240 images

per minute.

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://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.

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Scanning—Photographing Photos

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.

As the liner CDD moves

from right to left (top

row), the image is

captured a line at a time

(bottom).

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 photosites, 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).


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Scanning—Photographing Photos

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 8½ 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.

Tip

Since the dynamic

range of a scanner

is specified by the

manufacturer and

not an independent

authority, the numbers

are always a

little suspect.

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


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Scanning—Photographing Photos

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 scanner courtesy of

Nikon.

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 x

4000—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.

A substitute for a film

scanner is a slide

copier—but they are

hard to find. Courtesy of

Ohnar.

A substitute for a

flatbed acanner is a

copy stand. One of

these also lets you

photograph objects that

can’t be scanned.

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.


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Scanning—Photographing Photos

Umax has a variety

of scan frames that

simplify scanning slides

and transparencies, and

help avoid newton rings.

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 scanner courtesy

of Fujifilm.

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.

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