Four 1200 dpi Scanners Under Scrutiny – THG.RU

Introduction

If you take a look at how a scanner works, you’ll realize that nowadays there is no justification for buying the most expensive model. Here are four of the most recent ones:

• The CanoScan D1250U2 is the first scanner for general use that is compatible with the new USB 2.0 interface. In North America, this model is sold as D1250UF, which includes a USB 2.0 PCI card and an adapter unit for scanning transparencies.
• The Epson Perfection 1250 is the successor to Perfection models 1240 and 640. The 640 is still considered by many to be the best in its class.
• The ScanJet 4470C is marketed by HP as a “reliable and affordable scanner, as simple to configure as it is to use.” It is supplied with a module for scanning slides and transparencies.
• The Umax Astra 4500 claims to be a speedy workhorse at a very low price. Certainly it was the least expensive model in our selection.

All four of them share an optical resolution of 1200 dpi and 48-bit color-coding, and all are USB compatible. In other words, all of them ought to be capable of producing good-quality scans at low resolution (website images) and at high resolution (retouching and enlarging photos).

In order to compare them, we timed them on the following tasks:

• pre-scanning an A4 page
• scanning a 10 x 15 cm photo at 72 (or 75), 300, 600 and 1200 dpi
• scanning a photo from a magazine at 300 dpi
• scanning a postage stamp at 1200 dpi and 2400 dpi (an interpolated resolution in this case)
• scanning an A4 photograph at 300 dpi

The test for quality consisted in comparing all the previous results, as well as:

• evaluating the color rendering of the optical system, based on our test patterns
• considering the scanners’ ability to scan 3D objects

The Current Situation

Ten years ago, scanners were incredibly pricey, and so they were only used by professionals to digitize images. Flatbed scanners were made accessible to the general public five years ago when a psychological price threshold was set at $150, which remains unchanged. Optical resolution was only 300 dpi at the time, but in general, this was perfectly adequate for most uses, such as web page illustration, optical character recognition (OCR), photo reproduction (without enlargement), etc. Today, the scanner has become a standard for processing graphics, even for the home user, and is probably the most important piece of equipment, next to the printer.

As in all sectors, competition is fierce! Manufacturers are constantly coming up with innovative features and making improvements in order to gain a greater market share. But not all of them have continued the fight; several have thrown in the towel. Who is to blame? Fierce competition is one culprit, and second is the very low profit margin, which, according to the manufacturers, is due to pressure from the chain stores to keep costs low. As an example, Agfa, one of the market leaders, announced last September that it was no longer going to compete in the mass market. No more scanners for them!

So, to get back to the subject at hand:

• Minimum resolution is currently 1200 dpi and may well increase to 2400 dpi by next year.
• All the models now on sale claim 48-bit color coding, implying accurate color-matching.
• The price range of the cheaper models remains the same (between $40 and $150).
• The advent of the USB 2.0 interface has substantially decreased processing time.
• The number of manufacturers currently on the scene is getting smaller by the month.
• The market has shrunk so that only the big names are still around.

But, far from being reassured by the fact that their position grows stronger by the day, the surviving manufacturers are on edge because multifunctional peripherals (combinations of printer + flatbed scanner) are about to push scanners out of the picture. The biggest optimists give them another five years, but the pessimists are talking about a period of survival of no more than one year… In fact, it would be hard to imagine individual users wanting to own scanners when the “all-in-one” machines are going to cost no more than $150, i.e. more or less the price of a scanner on its own.

How It Works

A flatbed scanner is little more than a hollow box, containing a mechanical and optical system that illuminates documents placed on its glass plate. The reflected light is captured and dispatched to a computer in bit form by an analog/digital converter.

In this context, the key points in choosing a scanner are its resolution on the one hand, and the number of colors it is capable of managing on the other. If you take a closer look, you’ll notice that both these details are clearly indicated in the product specifications, but still have to be assessed in various ways. Sometimes the results are quite surprising. Even if all the scanners currently on the market are of the same type, there are two basic families:

CCD Scanners

This is the largest family, and the four scanners reviewed here belong to this category. With this type, the light reflected by the document being scanned is reflected by a system of mirrors to a lens, which has the job of streaming the image to a CCD (charge-coupled device) detector. This is a fragile, accurate and quite expensive system, since the mirrors must always be perfectly aligned and the lens must be of the highest quality.

CIS or LIDE Scanners

CIS (Contact Image Sensor) or LIDE (LED Indirect Exposure) scanners, developed by Canon and Umax, are two and three times more precise than their CCD counterparts, due to the fact that they do not need the set of mirrors. This is replaced by a simple CMOS detector bar that covers the whole width of the page. This bar is located a few millimeters below the glass panel, and directly captures the reflected light without it passing through any secondary system or lens. An additional advantage is that these scanners are less sensitive to shock and the technology less expensive. There is a disadvantage however, in that CMOS detectors are less sensitive than CCD detectors, which translates into less color accuracy. Another feature with these detectors is that they require very little power. That is why most CIS and LIDE scanners are powered solely via the USB cable and do not need an external power supply.

A Few More Details

The manufacturers emphasize the following features as selling points for their scanners.

Resolution

The first is resolution. This is always expressed in dpi (dots per inch) and indicates the number of dots that the scanner is capable of capturing in one square inch (2.54 cm on each side). It often takes the form 1200 x 2400 dpi. The smaller of the two figures refers to the sensitivity of the detector, and the second (the larger) refers to the number of movements that the optical system is capable of performing as it moves along an inch at a time.

This statement is misleading because what’s written can’t always be taken literally. The true working resolution is always a square of values. If you want to work at 1200 dpi, the system will do so by making 1200 upward movements, not 2400 as the specification might lead you to believe. The fact that a scanner is capable of performing 2400 upward movements is only relevant for the interpolated resolution of the scanner. A 1200 x 2400 scanner is likely to produce better results than a 1200 x 1200 dpi scanner if you work at an interpolated resolution of 2400 dpi. This has absolutely no effect when working at 72, 75, 300, 600, or 1200 dpi.

Depth of Color

The detectors installed are of the RGB type. This means that each pixel is described by three factors, namely, its value in red, green, and blue. Each of them is generally 16-bit encoded, hence the statement in the specifications of a color depth of 16 x 3 = 48 bits. That’s being slightly economical with the truth! A distinction should be made between the internal depth of color and the so-called external depth. If it’s of the external type, this means that an image sent to the PC is actually 48-bit encoded. It’s therefore up to you to convert it to a format that is capable of handling such a large amount of information, although, as you know, a JPEG, for instance, would not be capable of doing this. If it is internal, this means that the detector is sufficiently sensitive to work at 48 bits. But nothing is said about what is actually transmitted to the PC. The message might only be transmitted with 24-bit encoding, for example.

Nevertheless, this point affects the quality of the scan. Although it’s said that CCD peripherals are generally considered to be more accurate than those based on CIS technology, all flatbed scanners lose a certain amount of sensitivity. The information lost en route is quite substantial. First, it occurs via the passage of light through the glass plate. Part of the light is reflected and passed back through the same glass plate. Once it has been reflected in the mirrors, the image passes through the lens. So, for the optical system alone, three steps are necessary and each of them adds to image deterioration. Then there is the decoding by components on 65,536 levels, which is really little more than an attractive sales pitch, and really due to the fact that manufacturers are so eager to offer more and more features that they have found themselves forced to economize on all components. Lens quality has suffered in particular, and the mechanical system has become more fragile, the classic problem being that the scanning carriage tends to stop moving. And so on. Everything becomes an excuse for saving money, as well a chance to reduce product quality in order to offer a greater number of more exciting features. That’s why some of the optical 600 dpi models, such as Epson’s Perfection 640, are far better than a number of 1200 dpi scanners.

Pre-Scanning At 75 dpi

The results obtained here varied widely. The Astra 4500 is almost four times faster than the Perfection 1250U and twice as speedy as the HP and Canon scanners. The D1250U2’s USB 2.0 interface has no effect; not much time is gained in comparison with the times measured in tests using USB-1.1 compatible scanners, and, in the real world, even less time would be saved.

Above: the scanned photo. The example shown is the scan (very slightly reduced so that it fits on the page) that was produced by the HP ScanJet 4470c, which, in our opinion, is best at 75 dpi.

The examples shown below and on the following pages are life-size excerpts of images scanned at the various resolutions that are specified in the caption.

Sections scanned at 72 or 75 dpi (depending on what the driver offers).

Speed at 300 and 600 dpi

At 300 dpi, the differences in speed are much smaller. The D1250U2 operating on a USB 2.0 connection is the winner, followed closely by the Astra 4500. The slowpokes are the HP, Epson and the D1250U2 tested on a USB 1.1 interface.

The USB 2.0 really only comes into its own from 600 dpi upward. It is then that the D1250U2 greatly outshines its USB 1.1 rivals.

Sections scanned at 600 dpi

Extract 2

1200 dpi Photo, Postage Stamp at 1200 and 2400 dpi

Once again, the D1250U2 with USB 2.0 outshone its rivals. Here are some of the details:

• the ScanJet 4470c had very reliable color when scanning detail at 1200 dpi
• the D1250U2 won consistently
• the Astra 4500 did very poorly at 2400 dpi

Details of the Photo

Sections scanned at 1200 dpi

Section 2

1200 and 2400 dpi Postage Stamp (Excerpts)

Details of a postage stamp at 1200 dpi

Details of stamp at 2400 dpi

Color Fidelity

Scores for color fidelity were obtained from the following test:

We scanned a grayscale consisting of 20 shades ranging from white to gray (coordinates 0 x 255) to pure black (19 on the horizontal axis, 0 on the vertical axis). Each shade is composed of the primary colors red, green, and blue. Once the pattern had been scanned, we broke it down into images in red, green and blue, and then we compared them with the theoretical values. A perfectly calibrated scanner would produce an RGB image of gray no. 10 with equal value and thus equivalent to 121.

In each of the following graphics, the white line represents the ideal, theoretical line. The red line records the red components of the scanned pattern. The green line represents the green component, and the blue line represents the blue component.

How should the curves be interpreted?

The further the RGB curves are from the white line, the greater the color changes made by the scanner.

If the RGB points are below the theoretical white point, the scanned dot is darker than the original. If the RGB dots are above the white point, then the scanned area is lighter than it ought to be.

Finally, the scanned pattern was in perfect gray, and the RGB elements for each point were supposed to be equal. Thus, the RGB curves ought to be perfectly superimposed.

In the case of the Astra 4500, at dot 10, the red dot is lower than the blue and green dots, indicating a tendency in the scanner to add too much red to this gray, with a risk that all the images will be slightly redder than they ought to be in other patterns.

The D1250U2 was the winner, with RGB curves that were almost perfectly superimposed.

The color balance (which indicates whether the RGB curves are superimposed or not) is 9.14 / 10.

The RGB curves are quite close to the white line. There is thus a good degree of color compliance: 6.94 / 10. The further the distance between the RGB curves and the white line, the lower the grade.

Hence the average final grade between the two grades of 8.1 / 10 as shown in the table at the top of the page.

How should the curves be interpreted?, Continued

Color balance score: 8.09 / 10

Color fidelity score: 6.07 / 10

Average for these two grades: 7.1 / 10

Color balance grade: 7.73 / 10

Color fidelity score: 7.45 / 10

Average for these two scores: 7.6 / 10

Color balance score: 5.86 / 10

Color fidelity score: 7.60 / 10

Average for these two scores: 6.7 / 10

When studying the four curves, you’ll notice that a major defect of these scanners is that they don’t make very faithful reproductions. Other types of imaging equipment perform much better. Although the white balance is very well managed, the same test performed on a digital camera produces much better results. This is due to the loss of light when it has to pass twice through other surfaces, the glass plate, the imperfect lens, the converter, etc.

Scanning 3D Objects in A4 Size at 300 dpi, Descreening

CCD scanners are capable of scanning 3D objects, at least in principle. We wanted to check this out using a cell phone. The image shown above has been reduced in size to enable it to fit the page. The following extracts are taken from the actual scan size.

Descreening

The Descreen function is used to remove the moirй effect that occurs when scanning pictures and photos from printed matter. Here, we can see that the Canon and the Umax scanners perform better than the other two contestants. For the Epson and the HP scanners, it necessary to apply a slight blur effect by using image editing software such as Photoshop.

Scanning Quality

Score (1-10)

With regard to scanning quality, these four models can be split into two groups. On the one hand, there were the Canon, Epson and HP, and on the other hand, there was Umax, all by itself. The difference is all the more striking if you consider the scores for color fidelity. The Astra 4800 performed slightly less impressively than its rivals, but did quite well nevertheless. A subsequent test often improves upon a previous result that was not as good. None of the four models chosen were far ahead of their rivals.

To sum up, the Astra 4500 works very fast, but at 75 dpi, its performance is poor. The opposite is true of the Canon D1250U2, which is in pole position in terms of both speed and in offering the most accurate digitization at 1200 and 2400 dpi. On the other hand, tests performed at 75 and 600 dpi are less impressive, since the colors turn out rather drab.

The ScanJet 4470c seems to be the ideal scanner if the scanned photos are only viewed onscreen – for web sites, say. Tests performed at 75 dpi are fast and very nice. The scanning function is rather disappointing however, because the application has a slight tendency to blur the images, but this isn’t terribly serious, since it is easy to touch this up in Photoshop, which captures the image perfectly. Finally, we did not test scans of slides for either the Perfection 1250 or the ScanJet 4470c. You should check this function out for yourself if you need it.

Canon CanoScan 1250 U2

This is not the only scanner in its category, but it is likely to be the least expensive for what you get. The CanoScan D1250U is sold in North America in the D1250U2F version, priced at $199, with a USB 2.0 PCI card. In theory, this means output multiplied by 40. In practice, we measured improvements in processing times of 15%, up to nearly 70%. When tested successively on a USB 1.1 interface and a USB 2.0 interface, the D1250U proved to be consistently faster in the second configuration. The acceleration is not particularly noticeable at low resolution (75 dpi), less than 20%. It is more obvious at 300 dpi, when scanning is up to 60% faster. The greatest improvement was noticeable at the highest resolutions, namely 1200 and 2400 dpi.

Except when operated at 75 dpi, connection to the USB 2.0 interface can be said to be responsible for increased processing speeds of around 60% – provided , of course, that the computer is compatible with the new interface. Canon recommends the installation of an Adaptec USB2connect 3100LP, which is not supplied with the scanner. We used this card in order to perform our tests using the new interface.

The PCI Adaptec USB2 connect 3100LP card.

Regarding functionality, the D1250U is a successor to this manufacturer’s previous models. Two driver interfaces are available, but the first so-called “simple” driver can be disregarded, since it is restricted to resolution management only. It is better to switch to the “Advanced” mode, which contains far more parameters, such as contrast, gamma, moirй, etc. There is also the Qare function. This was present on some previous models, and is designed to clean up scratches and dust on photos. During the scanning process, the scanner compares the set of colors captured and checks to see if they are logical. It then corrects the image if there are clear discrepancies. As might be expected, the process is not 100% reliable – far from it. In some of our tests, this feature did nothing to improve the final image, which actually lost sharpness. Other tests proved conclusive, however, because the quality was surprisingly good – so much so that you might think it wasn’t the same photo, that we’d used a flawless original.

The D1250U is the most reliable scanner in terms of color-rendering. It also produces the best high-resolution scans. In short, this scanner is a runaway success. It ought to meet user expectations if they intend to use it for what it is best suited, as a 1200 dpi optical scanner! If it is only used for 75 and 300 dpi scans, its full potential will never be exploited. Other scanners, such as the HP, might be slightly better for this type of use. On the other hand, anyone who needs optimal quality will always be prepared to spend the money on it. As color-faithful as it is, the D1250U tends, as usual, to darken the intermediate shades. It also has an irritating tendency to lighten the darker shades. So, while the D1250U is the best of the less expensive scanners, it’s not quite perfect. But we didn’t expect it to be perfect anyway, in view of its extremely reasonable price.

Note for users of the previous N1240U: the D1250U provides truer colors and is much faster.

Note: two color profiles are offered in the driver. Tests were performed with one that is “recommended” by default. The second optional driver is called Canon Color Matching. It seems to be of limited use, however, since the colors here turn out to be less true (more saturated) than with the recommended driver. By default, the color fidelity score decreases from 8.1 / 10 to 6.3 / 10 when the new profile is activated. As with the default profile, the darker shades are noticeably rendered too pale.

Epson Perfection 1250

Our favorite scanner used to be the Perfection 640, but it disappeared from the shelves this fall and was replaced by the 1250, with an improvement in optical resolution from 600 to 1200 dpi.

The Perfection 1250 is a good product but, in our opinion, not as good as its predecessor, the 640. We liked the previous model for its exceptional speed as well as for high and low resolutions. The greatest differences are at 75 dpi, a resolution at which the 640 was at least three times faster than the 1250. There is nothing to compensate for this loss of speed either, although scanning is slightly faster on this new model, there is no noticeable improvement in the quality of the scan. The interpolated 1200 dpi of the 640 was only as good as the optical 1200 dpi of the 1250 – in short, a disappointment.

Leaving the 640 and taking a look at the 1250 and its 1200 dpi rivals, the results are no better. Even if you take no account of the super-fast Canon D1250U2 because of its USB 2.0 interface, Epson’s1250 is four times as slow as the Astra 4500 at 75 dpi. The difference is not as great at 600 dpi, though the Umax is still faster, even then. In short, only the HP scanner works as fast, and that is not necessarily a compliment.

The scan quality is reasonable but, yet again, not outstanding. The color-rendering is slightly better than that of the Umax model, but it is not as good as that of the HP and Canon scanners. In short, the1250 is accurate but not very interesting in its stripped-down version. The 1250 Photo is preferable; it is only slightly pricier and has a backlit module for scanning film.

HP Scanjet 4470c

HP once decided to produce efficient but rather crude scanners. Design was obviously a secondary consideration for this manufacturer, who didn’t even attempt to hide the fact! But strategies have since changed. The 4470c is a good example: it has a very attractive aerodynamic design, is dotted with buttons, attractive colors, a backrest for slides, and even a miniature LCD screen that is frankly not indispensable, but nevertheless welcome.

While the aesthetics of this scanner are commendable, this is far from the case with the driver, whose interface seems to have been inherited from Windows 3.1. Using the excuse of an attempt to simplify its use to the maximum, HP has limited the default parameters available to the bare minimum. So much so that, if you are not happy with the interface as it is without venturing into the menus, you will not even be able to choose the resolution! If the scanned image is in color, the resolution will be only 150 dpi.

Therefore, your initial reaction when launching the driver for the first time is to resort to the Tools menu and activate the “change resolution” option. This action will result in the appearance of a free-floating scroll menu that is indispensable because it lists the available resolutions, from 75 through 2400 dpi. Once you have made your choice and finished scanning, the driver closes automatically. This is useful if you only have one scan to perform, but frustrating if you intend to do a series of scans. But worse is yet to come: if you want to capture a series of photos from magazines, this is what you will have to do for each photo:

1. Open the driver.
2. Automatic pre-scanning begins, 13 seconds, which cannot be stopped. The carriage returns to the starting point, which takes 8 seconds.
3. Go to the Advanced menu and select “Descreen.”
4. Automatic pre-scanning begins again, which takes another 13 seconds, and again, it’s impossible to stop. Carriage returns to its start position, 8 seconds.
5. Then, finally, you can start scanning, which takes 24 seconds, and your image can then be saved, but you must go right back to step one for the next photo.

As you can see, it’s a pretty slow process (more than one minute per photo!) and not exactly optimized.

Fortunately, the scanner does much better on other points, starting with its very good work at low resolution. When used at 75 dpi, the 4470c is quick and reliable. The colors are bright and sharper than those of its rivals. The main defect, when all’s said and done, is the same as that of Epson’s Perfection 1250: an inefficient scanning procedure and slowness at resolutions above 600 dpi. As for the scanning itself, the processed image can be improved by softening it slightly in Photoshop. But this involves more manual settings, of course.

Umax Astra 4500

(Not available in North America)

The Astra 4500 works very fast at low resolution, but not very satisfactorily. It is at least four times faster at 75 dpi than Epson’s Perfection. And yet the latter scanner is preferable, because the image delivered is poor and lacks sharpness. Apart from this, the Astra 4500 handled itself well on all the tests. As for quality, it is average, although without any notable weakness. There is simply a tendency to veer into the red. So if you choose this scanner, be sure to learn how to use retouching tools.

Similarly, although we think it a good idea to avoid the lowest resolutions, it does not do well at the highest resolutions, either. This is rather limiting if you know the optical specifications, but it is preferable not to use it at 1200 dpi and even less so at 2400 dpi. Scans at such high resolutions lack accuracy and the red is markedly too bright.

It is best kept to standard use. When used for 300 and 600 dpi images, it does perfectly well. The Astra 4500 is thus fine if you want to use it for storing family photos or scanning text documents.

Conclusion

(*) only sold in North America in the D1250U2F version, with a PCI USB 2 card and an adaptor for transparencies

(**) Not available in North America

Scanners are currently in an awkward position, because they are swiftly being overtaken by multifunctional equipment, and this is happening at the very moment when new interfaces are being introduced. Only Canon has reacted promptly, by offering an economical and innovative product that is USB 2.0-compatible. The D1250 U2 is thus the hands-down winner by virtue of its extremely fast processing speed combined with its accurate digitization. As long as you purchase a separate USB 2.0 PCI card, you will have the best value-for-money scanner on the market.

Second in line is HP’s ScanJet 4470c. We were particularly impressed by the high quality scans at 75 dpi. Unfortunately, it’s quite slow at 600 dpi and over. Furthermore, it would have been a good idea for HP to develop its driver a little more. The driver supplied with the equipment is seriously out of date.

Epson’s Perfection 1250 is rather deceptive. We still remember the Perfection 640U. The 1250 does not do much more, although it is slightly faster at scanning images. In other tests, the 640 was generally, and by a wide margin, much faster than this new scanner and despite its lower resolution, just as accurate.

The Astra 4500 is the least expensive but also the most limited of the four models. It would be better to leave it for routine work at 300 or 600 dpi. The scanning process, however, is quick, but it is rather disappointing because it is less accurate that that of its rivals. Furthermore, scanning with the test model tended to veer into the red. Despite all this, it is not a bad buy when compared to the others. You will save a few pennies and have a scanner that is perfectly good in the lower, more frequently used resolutions.