Hewlett-Packard ScanJet 4100C USB flatbed scanner

Review date: 4 December 1998.
Last modified 03-Dec-2011.


Oh, I don't know about this.

Hewlett-Packard used to be run by engineers, dammit. They made things with pointy corners, and incomprehensible packaging you needed a PhD in applied topology to put back together again, and 4,003 features including complete Reverse Polish Notation programmability.

hp4100c160.JPG (8169 bytes)
Yes, you can take those garish stickers off.

Now they're making funky looking slopey scanners with swoopy curves and cute aquamarine buttons. What's the world coming to?

What you get

If you do not share my prejudices about the Reprehensible Decline of Form Following Function, you'll probably quite like the look of the ScanJet 4100C, HP's current lowest cost flatbed model. The curved front makes it easy to lift the lid, the buttons are readily accessible, and nothing else has been mucked about with. I've got no idea why they decided to make the scanner bed slope towards the front, but this doesn't matter unless you're scanning marbles or something. You can always jack the front up with a magazine, anyway.

The HP scanner's primary claim to fame is that it's one of the first scanners to use the Universal Serial Bus (USB) interface. Pretty much every PC made in the last year or so has USB ports, but most of them are currently sitting there empty, which is a shame because USB is a really elegant, simple way to connect large numbers of low to medium speed peripherals like modems and mouses and cameras and scanners.

Most low-end scanners, like for example the bargain basement Avision 260C, reviewed here, are parallel port devices. They usually have a passthrough port for a printer, and work passably well. But they're not terribly fast, and tend to paralyse the computer while they do their thing. More expensive models use the Small Computer Systems Interface (SCSI) protocol, which is very fast but requires a SCSI interface card for the PC. USB is a very handy innovation. If your computer lacks USB ports, you can get an expansion card with a couple of ports on it for $100 (Australian dollars) or less.

The USB connection also promises to make the 4100C compatible with Apple's USB-equipped iMac, but the included software is only for Windows, and HP do not appear to offer a Macintosh driver.

Setting up

Ideally, USB is supposed to be completely plug-and-play; you connect a new device, the computer maybe finds the driver software itself but probably asks for the disc that came with the new gadget, the driver's automatically installed, and you're off. No need to turn the computer off to connect or disconnect the device, no need to have the device on when the computer's turned on, no muss, no fuss.

The 4100C's implementation of the system is nearly as good. You need to run the driver installation software before you plug the scanner in. Once you've done that, it just works. Presto.

Those two cute buttons have a function. This is HP's entry level home scanner, and the strong emphasis in hardware and software is simplicity. With most scanners, you have to put what you want on the scan bed, then run a paint program or something else that can take scanner input, then use the Acquire option in the File menu to access the scanner's TWAIN driver (which you previously have to install with the other scanner software, then manually select in the programs you want to use it), then set the resolution you want to scan at, then do a pre-scan, then draw a box around the thing you want to scan, and maybe tweak the brightness or gamma, then do the scan.

With the HP, you stick the thing you want to scan in the scanner, then hit the scan button. The PrecisionScan LT driver software runs, automatically pre-scans, automatically highlights the object on the scan bed, automatically figures out what it's looking at (photo, line art or text), automatically chooses an appropriate colour mode and resolution, and asks you where you want to send the scan - to one of a list of programs or to a file. You can send your scan to an image editor, a fax program, or a word processor. If you choose a text handling program, PrecisionScan automatically applies Optical Character Recognition (OCR) to the image and outputs text.

If you hit the print button on the 4100C, the scanner pretends to be a photocopier - it scans automatically and sends the output straight to your printer, which of course makes it a colour copier, if you've got a colour printer.

Vital statistics

In common with many low cost scanners, the HP's optical resolution is 300dpi and its mechanical resolution is 600dpi. This is more than adequate for home, business and indeed most professional use. It has 36 bit colour, and comes with Adobe's PhotoDeluxe - essentially a cut-down, simplified, automated version of PhotoShop - and Caere's excellent OCR software, a cut above the superannuated packages included with bargain scanners, is built into PrecisionScan LT.

The 4100C's scan bed is 8.5 by 11.7 inches, making it big enough for both A4 and letter size paper.

The HP's scan speed is ordinary - it took one minute and 20 seconds for a full bed scan at 300dpi, against less than a minute for the budget parallel port Avision 260C, which has the same size bed. But because of the 4100C's USB interface, doing scans doesn't stop you from doing other things with the computer; parallel scanners force you to sit and wait as they scan. The HP scanner always does a ten second lamp warmup before its pre-scan, so pre-scans are also slower - about 40 seconds, versus a mere 12 for the cheaper Avision. The extra 20 seconds or so is because PrecisionScan pre-scans at 150dpi, a much higher resolution than most scanner drivers use, in order to do its clever image analysis tricks. If you just want to knock out a load of scans, this is a pain.

Fighting the driver

Shiny coin test
A creditable result on the dreaded shiny-coin test.

For most home and small business users, the 4100C/PrecisionScan combination is a brilliant system. By and large you can count on PrecisionScan to figure out the right dots per inch and colour mode, and it's also pretty good at finding the object on the scan bed. In my tests it did well with normal jobs - colour photos, black and white documents, but identified various odd objects incorrectly. For instance, it decided a green circuit board - I scan a lot of expansion cards - was a black and white photo. It also unhelpfully "straightened" scans of 3D objects when it found elements that looked as if they were crooked, when they actually weren't, because it wasn't allowing for perspective.

If PrecisionScan gets it wrong, you can change the basic settings - but if you do a lot of scans that the software can't figure out properly, you'll grow to hate it. Custom resolution and colour settings are remembered for each PrecisionScan session, but when you close the scan driver it forgets the custom settings and picks automatically again the next time you press the scan button. It is impossible to change settings before you do a pre-scan, only after it's done it and decided on some automatic settings. It is also impossible to just stick a document in and scan it without a pre-scan. And if you're in a hurry and put a small item at the top of the scan bed, then allow the pre-scan to proceed until you see all of the thing you want to scan, then abort the pre-scan, PrecisionScan erases the partial pre-scan image. Nice one.

On the plus side, that slow, high resolution pre-scan gives the scanner software a ready-made 150dpi scan of the bed, which it can pump straight out without rescanning if the already-acquired data is good enough for what it needs to do. So you have to put up with a slow prescan, but the actual scan time is often zero!

Another time-saver is PrecisionScan's handling of multiple items in one scan. if you want to scan two or more things that all fit on the scan bed at once, you can do it - and, again, if 150dpi is good enough (and it likely is), you can just send them all wherever you want them, as individual images, without any more scanning.

By default, asking for a higher resolution than 150dpi is likely to result in PrecisionScan doing an ugly interpolation enlargement of the pre-scan, but you can easily set it to rescan every time, instead of just when you ask for a much higher resolution version.

Stretched blank scan
Since the 4100C doesn't cheat by making all of its brighter tones pure white, stretching the tone detail of a blank scan gives you this. Don't worry - the unprocessed scan looks nice and white, and there are no imperfections of note.

So, overall, PrecisionScan performs as advertised. But if you're not happy with its automatic sharpening and colour correction and other fudging about - tough. You can't turn the auto features off, and you can't tweak the settings. I never noticed PrecisionScan doing anything really terrible, like erasing colour detail in a scan because it thought it was looking at a block of an even shade (this is a feature, not a bug - it makes things like coloured logos come out better), but that doesn't mean it never will.


If you're looking for a click-and-go scanner with excellent image quality and good bundled software, the HP ScanJet 4100C is well worth the extra cost - it sells for around $550 (Australian dollars). If you already know how to use scanner software, though, and commonly need to do unusual jobs, the simplified driver will annoy you immensely. A scanner that costs half as much will give much the same output quality, provided you can can put up with a parallel port interface.

All of my complaints about this scanner would go away if only PrecisionScan LT offered an "advanced" mode that worked like every other ordinary scanner driver on the planet. But since it doesn't, and since there does not appear to be an alternative driver available, the ScanJet 4100C remains a scanner for the masses, not the pros. For the money it's decent, but not fabulous, value.




  • Good idiot proof low cost brand name package
  • USB connection is fast and simple.
  • Driver software can be annoying if you know what you're doing



Gamma: Adjusting the "gamma curve" of an image or of an image acquisition device gives you a way of brightening or darkening without losing as much detail as a straight brightness adjustment. Gamma adjustment works by changing the brightness of pixels according to how bright they currently are - the closer a pixel is to the extremes (black and white) the less it's changed, with the largest changes for pixels at the 50% grey level.

Interpolation: Every cheapo scanner in the world has some preposterously high resolution figure on its brochure, which tells you the maximum image resolution you can dial up in the scanner driver software. The actual maximum resolution of the scanner is determined by its optical and mechanical resolution, but the software can duplicate pixels to give the impression of much higher resolution.

smiley.GIF (58 bytes) smileybig.GIF (2120 bytes)

The smiley face on the left is an 11 by 11 pixel image, blown up to 55 by 55. The image on the right is an interpolated 55 by 55 version, in which the darkness of each pixel is determined by means of a clever algorithm that works from the darkness of its neighbours. 

Mechanical resolution: Flatbed scanners move their scan heads past the document to capture its image. Since the document isn’t changing, taking lots and lots of horizontal-line snapshots of it and sticking them together gives the same result as a far, far more expensive capture mechanism that could grab the whole image at once. The mechanical resolution of a scanner is the smallest step by which it can move the head, and it thus determines the maximum number of these skinny snapshots that can be taken. Mechanical resolution does not have to be the same as optical resolution.

Optical resolution: A scanner’s optical resolution is the number of dots per inch (dpi) its scan head can detect. A scanner with 300dpi resolution and a scan head 8.5 inches wide has a scan head 2550 dots wide.

36 bit: Most cheap colour scanners are 24 bit; they digitise each of the red, green and blue channels with eight bit resolution, making a total of 24 bits per output pixel. 36 bit scanners add another four bits of resolution to each channel, increasing the number of distinct colours they can output from 16777216 (two to the power of 24) to 68719476736 (two to the power of 36). This 4096-fold increase is invisible to the naked eye, but it means the scanner can use only a portion of the colours it detects and still maintain full detail. If, for instance, you push up the brightness of the scan in the driver software by 20%, the top 20% of pixel values will all run "off the top" of the permissible output values, and become pure white. A 24 bit scanner, in this situation, has to stretch the remaining 80% of pixel values into a complete 24 bit gamut, reducing image quality, but a scanner with 36 bit resolution has values to spare.

TWAIN driver: TWAIN stands for Technology (or Toolkit) Without An Interesting Name. No, really, it does. Who says programmers have no sense of humour? Anyway, a TWAIN driver is a piece of software that a paint or optical character recognition or other graphic-related program can call upon to deliver an image. The image may come from a scanner or a digital camera or anything else; the driver talks to the hardware and provides the user with its own interface, then delivers the final picture to the invoking program.

Give Dan some money!
(and no-one gets hurt)