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All About Scanning
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1. What is a scanner?
A scanner is several things all in one. Given that you have a color printer and a fax modem hooked up to your computer, a scanner is an Image editing machine, color copier, fax machine and can even take text that you may not want to re-type and OCR it . We will get into the OCR portion of scanners a little later.
There are lots of things scanners can do that you may not
be aware of or that come as optional accessories such as Automatic Document
Feeders (ADF) or Transparency Media Adapters (TMA). These
devices have their specific duties and may come in handy somewhere down the road, so make
sure whatever scanner you purchase that it will have the capabilities to "grow"
with your changing needs or you might be throwing your money away. An ADF attachment to
your scanner comes in handy for people who have large amounts of text, OCRing, or faxing
to do. When deciding on an ADF make sure you get one that:
A) Is fast
B) That can hold at least 25 pages or more
C) It does not jam up all the time
Transparency Media Adapters (TMA) sales
have been growing more and more by the day. Why are they so popular? More and
more people are learning that they have a lot of 35mm slides laying around and tons of
negatives that may be useful to "preserve" for future use and since we are in
the "digital age" they may wish to preserve these images for future generations
etc. We have noticed a large increase in TMA's for medical and dental use. Doctors
and Dentists are realizing the value of such a tool so that they can enlarge a specific
area of a problem on an x-ray and even e-mail this picture to a colleague who may be
thousands of miles away for a second opinion etc. Dentist also like them for the same
reason. Some scanners have these built into the lid of the unit while some (better ones)
replace the lid of the scanner when needed. New tray TMA's pull out from the middle of the
scanner and produce some of the nicest transparencies we have seen. When shopping for a
TMA make sure of the following:
A) Will the TMA be able to do the size of the transparent image?( i.e. 4" x 5" ,
X-Rays or just smaller transparency's such as 35mm or negative strips) Do not under
buy a TMA.
B) Is the TMA just a lit light source or does it move in sink with the scanning lamp?
C) Is the TMA built into the scanner (such as a tray holder) or is it something that
attaches and plugs into the rear of the scanner and replaces the lid?
D)There is another alternative to buying a transparency adapter for your color flatbed
scanner. They are called "Dedicated Film Scanners". These units are made
strictly for the purpose of scanning 35mm slides and negative films. Several
considerations should be made before purchasing a dedicated film scanner such as the size
of the transparency. Most only do 35mm (in the card board borders or out) and negative
film, such as you get with your processed film from your local film developer. Please
remember this, if you see a dedicated film scanner on our site (or anywhere else) for a
very inexpensive price, don't expect the quality and performance that you would get out of
a much higher priced unit. In other words, don't expect something for nothing. The lower
end dedicated film scanners may be just fine for doing scans to email friends or to place
on CD's through a CD-Rom writer, but they lack when it comes to doing nicer larger print
outs such as 5x7's or 8X10's. Usually the dynamic range (which is so important to
dedicated film scanning) on lower end units are very poor compared to a higher end
dedicated film scanner which are usually much better (Read more about "Dynamic
Range" in this article).
The nice thing about owning a scanner is the ability to store just about EVERYTHING on your computers hard drive instead of everything just taking up space around your home or office. There are some great programs designed to "manage" your documents and images for latter retrieval.
2. What do all the numbers mean?
NOTE: Before we discuss numbers, we need to give you a piece of advice here, if you are a Windows user, please make sure that your system's color pallet is set higher than 256 colors. Set it for 24 bit true color or at least 16 bit High Color. Anything less than this will make any image scanned look patchy or splotchy.
Numbers
This is probably the most misunderstood part of a scanner, the numbers! You
will usually see something like this: 300x600 or 600x1200 or sometimes a manufacture will
list them like this 600x600 or 300x300. Then on top of all that, you see 9600x9600
or 4800x4800 then the key word "Interpolation".
Let's take the lower numbers first. if you see 300x600 DPI this means the scanners highest hardware number (in this case 600) is the most "dots per inch" (dpi) the unit can scan through its internal hardware. In other words, if you scan an image at 600 dpi you will be getting 300 dpi horizontal and 300 dpi vertical giving you a total of 600 dots (pixels) in every inch of the image.
Now the first number in this example 300, tells you how many CCD's (Charged Coupled Devices) that are on your scanning lamp. A CCD converts a analog signal to a digital signal so that your computer can process the information it is getting from the CCD so that you can see the image! A CCD is an electronic sensor that's all. Getting the highest numbers for a scanner may prove to be more than what you may actually need. Don't get scanner dpi confused with a printers dpi. Agfa, actually uses the term "ppi" it stands for "Pixels Per Inch" and this makes more sense since a scanner, video card or monitor cannot show you dots, only pixels. Most people seem to think that if they have a printer that will print 1400 dpi that they need a scanner that will do the same. Nothing could be further from the truth. Scanning at a lower dpi's does not make the picture less appealing it makes it more manageable.
Interpolated resolution is done through your scanners twain software. What it does is simply this, when you have exceeded you scanners highest hardware number you are now into software interpolation. The software now starts to take over and to make it simple, it may see a red pixel next to a pink one and decide to put maroon in between both of them. It does exactly what it says it does, Interpolates for the hardware through the software. Do you really want software to give it's best interpolation of the original image? No way! Not to worry, you will probably NEVER use these numbers, and most are just hype anyway. Hence, never pay attention to the interpolated resolution, they are just there to impress you, don't let them.
Size is Important!
If you are scanning an 8" x 10" color photo the last thing you will
want to do is scan it at 600 or 1200 dpi. Our rule of thumb here at The Scanner
Outlet is simple, the bigger the image to be scanned the lower the resolution you will
want to scan it at. The smaller the image (when we say small we are talking about an
image of 1" x 1" or a slide or negative) the higher the resolution you will want
to scan it at. If we try to scan a large image at a high resolution we will create a
nightmare for several reasons. The first thing you will notice is how slow the
scanner will be going. It would take about 15 or 20 minutes to scan a photo at that
size at that resolution. The second thing you will notice is your hard drive space
will be in jeopardy and that half of it is now gone! The third thing (and probably
the most important thing) the image doesn't look any better it is just bigger! You
will literally upset anyone you try to e-mail this picture to because it will take them
forever to receive it on their end and now their hard drive is also full. If you are
planning to do regular photographs and images a 300 x 600 dpi scanner will prove to be
more than enough, they are great for people who wish to do web pages etc.. Again, only buy
a higher resolution scanner if you plan on taking a portion of your image and singling it
out or making it larger than the original. Higher dpi scanners are great for transparent
film also! If you need a high dpi scanner don't worry, you can always set the dpi lower
when you don't need the higher resolution.
24, 30,36, 42 &46 Bits
Most people seem to get the Bits of a scanner mixed up with the bits of their
operating system. Most people have a 32 bit operating system such as windows 95, 98,2000,
NT etc. But the bits for a scanner usually 24, 30, 36 or 42 are telling you how many
shades of red, green and blue (colors) a scanner is capable of doing. A 24 bit
scanner scans 16.7 million colors, a 30-Bit scans over 1-billion colors, a 36-bit scans
over 68 billion colors, divide all these numbers by 3 and that's how many shades of red,
green and blue (RGB) your scanners capable of scanning. The only limitations rest in
your systems video card, operating system and image editing software.
Most (99%) of all the computer systems designed today (1998) are only capable of displaying 24 bit color. The most colors your video card, operating system and software are capable of displaying for you to see or edit is 16.7 million colors, divide that by red, green and blue and that's how many of those shades of colors you will be able to see or manipulate. So why buy a 30,36 or 42 bit scanner? Let's put it this way, if you were the coach of an all star basketball team and you had a chance to choose from thousands of great basketball players but you can only play the best 5 out of those thousands wouldn't you?. What a team you would have! Same thing with a higher bit scanner, you will be breaking down trillions & billions of colors to millions and only retaining the best out of them. You will have the best shades of red, green or blue and the shadowing and highlighting will be better than a 30 bit scanner. If you plan on doing transparent film or negatives, and since you will be scanning small things and making them bigger, you will want a minimum of 600 x 1200 and at least 30 or 36 bits. Adobe Photo Shop 4.0 and higher is capable of handling at least 30 bit scans, the only problem is your video card and operating system will only display 24-bit max, even if your video card driver allows more choices than 24-bit high color or true color the most you will see is 16.7 million of them.
The Scanner's Dynamic Range
What the heck is dynamic range and what does it have to do with anything?
When you are shopping for a scanner, and you see all these different models
some have the same specs and numbers but the price seems to be way different between the
two. You immediately go to the lowest price one and say to yourself "
wow!, I am the best shopper in the world", "Look at me, I've found the ultimate
deal on a scanner". "Nobody else could do what I have just done!".
Well let us be the first to burst your bubble, you just might not know what the
other guy does, Dynamic Range is Important! Software bundles, warranty, speed,
quietness and the construction of a scanner are also reasons why a scanner may cost a lot
more than one with similar "specs" but most of the time Dynamic Range plays a
big part in the scanners price.
The best way to explain Dynamic Range is how PC Magazine explained it. Dynamic Range represents the scanner's ability to register both a wide tonal range and the granularity of adjacent tonal values. The dynamic range is manifested in the accuracy of captured details and in the smoothness of gradations between highlights and shadows. Also called the "signal to noise ratio, dynamic range is derived by computing the difference between the whitest and the blackest gray levels captured by the scanner (the signal) and dividing that value by the standard deviation in the white signal (the noise). The results are expressed on a logarithmic scale. Simply put, the scanners we have tested with the highest dynamic range numbers, are usually the best produced images since the "noise" is less the colors flow smoother and more accurate to it's final destination. You will always notice that high end dedicated film scanners that do 35mm slides and such always have a high dynamic range number. Look at the Dynamic Range as a threshold for pain and replace pain with noise and you'll get the idea. Images look sharper, better detailed in the darker areas and throughout the entire image than scanners with lower dynamic range numbers. For people who get into the best graphics imaginable, they are always looking for a high Dynamic Range number on their scanners.
SCSI (Small Computer Standard Interface), Fire
Wire, Parallel Port or USB (Universal Serial Bus), what type of scanner connection
do you need?
Well, these are some big words. When I was interviewed on Jeff Levy's KFI
on computers, (his Sunday morning radio show) he got a big laugh out of the word SCSI
(pronounced SCUZ-ZEE) he use to tell me that it sounded like a dirty un-kept person! Well
in scanner terms it is the absolute best way to control a scanner. It is also
(sometimes) painstakingly hard to set up, but it is the most rewarding out of the other
three choices. A SCSI scanner usually works on both PC and MAC computers and
is without a doubt faster than a parallel port scanner or USB scanner. There are
some great advantages in the others, but lets talk about SCSI first.
SCSI Scanners
A SCSI controlled scanner is good for two reasons first because of its greater
ability to process and deliver information quicker and secondly it doesn't mess with
anything else on the system such as your printer, zip drive, tape back up or anything
external that might be plugged into your systems parallel port, it works independently
just like a modem, video or sound card. It also works with Mac systems (who to this
day still have the best graphics display) and also for PC's (newer Mac systems such as
G3's and G4's now have available PCI SCSI Slots that now except SCSI cards) which means
you will have to install a SCSI controller card into you systems ISA or PCI slot (provided
with most SCSI scanners). Older Mac users love SCSI devices because they have a
"built in" SCSI controller in their systems which means they do not have to open
up their system to install a SCSI card, just plug it in and your ready (after installing
the software). Some SCSI cards can control up to 7 devices on the same chain (a.k.a. daisy
chain) while the newer ultra wide SCSI controllers can control up to 15.
Some of the problems associated with some SCSI controllers is that they may require an interrupt or DMA address that may be in use by some of the cards mentioned above. This can cause several headaches while you try and move address's around to accommodate your new SCSI card. With plug-n-pray it is getting a lot better and easier to do. One thing to remember is that when you operate a SCSI scanner, you might want to get into the habit of making sure your SCSI device (such as the scanner) is ALWAYS turned on before you turn on your system or if you are using windows 95, 98, NT etc. You can always go to the device manager and click on refresh so that you may use your scanner in the middle of your windows session and let your system renew it's search for your external SCSI device. Windows always likes to see a device as it is booting up, powered on and ready to go! Also, SCSI devices have a number for each device (usually selectable) and you do want to make sure no other SCSI device such as a hard drive or CD ROM drive are on the same number as your scanner.
USB Scanners
USB (Universal Serial Bus) is a great new innovative way to connect up to 127
devices on a single chain. Although it is faster and easier than a parallel port scanner
it isn't as fast as a SCSI scanner. Without a doubt it is the easiest way to install a
scanner. Once you plug it into your USB port your system should automatically see
the new scanner immediately and allow you to take the appropriate measures to install the
scanners drivers. These scanners are becoming very popular and with time should become
faster and even easier (if you can imagine that) to use. For people who have a need
for speed, they might want to get a SCSI scanner, but if speed is not the most important
issue you may have but still a necessity, USB may be the best of both worlds if you are
willing to compromise a little. If you have an I-Mac a USB scanner may be the way to
go, but how many external devices can one have anyway?
Some of the problems associated with a USB scanner is that most manufactures of USB devices are not putting a USB pass through on the back of their scanners. If USB is going to be such a great way of hooking up hundreds of devices, then why not put a USB in and a USB out (to the next device) on all USB devices? It makes sense. Another problem for PC users is that you must be running Windows 95B or Windows 98. They will not work with any other operating system at the moment. You must also have a system that supports and has a USB connection built into it already. Some older systems do have USB pins on their mother boards but they are not so "universal" they may not work like the newer ones do. Make sure your system has a USB connector attached to the back of your case and chances are you'll be safe.
FireWire Scanners
Newer, better, faster, easier, this is what we all heard about FireWire connections.
Well maybe yes, maybe no. The good thing about firewire devices is its ability to go into
one device and out to the next creating a chain. Another is its speed (it is suppose to be
faster than SCSI), but I failed to see ANY significant speed changes that would make a
difference between FireWire and SCSI. One major issue is not to many PC's have this
ability yet. Although you can go out and buy a firewire card, you might as well use the
open slot for a good SCSI card (most SCSI scanners come with one). Most new Macs have this
option with their newer systems but the older Macs do not. The price on firewire scanners
are expensive, only you can decide if it's worth it or not. Overall, I'd take a "wait
and see" attitude on one.
Parallel Port Scanners
Well what could be said about parallel port scanners that would make you
want to get one after hearing all the great things about the SCSI, FireWire or USB models?
First of all a Parallel Port scanner is EASY to hook up, they
can be moved from the computer in your office to the computer at your house to the laptop
on the road or just about any place where you may need one! They are by far the
biggest sellers (because of their price) and they work with just about any PC's operating
systems. For someone designing a web site or for people who don't plan on taking an
eye-ball out of a picture and blowing it up for a poster, a parallel port scanner can be
the answer to all your problems. Who scans at 1200 DPI anyway? Not a parallel port
scanner user. For the beginner a parallel port scanner is a viable option.
They don't cost and arm and a leg either, why not?
Some of the problems associated with a parallel port scanner are as follows: Speed, parallel port scanners are slower than USB, FireWire or SCSI. A parallel port scanner can make your printer get totally disconnected from the loop, sometimes requiring the user to resort to an A/B switch box which can be a real pain. Another problem lie's in your systems bios LPT settings, some older systems do not support EPP (extended parallel port) mode. This is the fastest way to run a parallel port scanner, but not all EPP modes are the same. In other words there is not a "standard" EPP mode when there are several types of bios chips in manufactures mother boards. Some Parallel port scanners will run in the SPP(standard parallel port) mode which most bios chips have, but then the scanners manufacture may not support SPP mode only EPP! Make sure when purchasing a parallel port scanner that it has a bi-directional mode and that it will operate in EPP, SPP, ECP or all of these modes. A great parallel port scanner is the Plustek 9636T because it supports all these modes and even combinations of them. It also has a very fast buffer. It even does 35mm slides and negative strips.
What is TWAIN?
You won't believe what TWAIN stands for. Ready? It stands for
Technology Without An Interesting Name! Believe it or not, that's what it stands
for! TWAIN is a driver that all scanner manufactures use to make the scanner perform
with any TWAIN compliant software program. ALL SCANNER MANUFACTURES MAKE THEIR OWN TWAIN
DRIVE. In other words, I couldn't use a Mustek TWAIN driver with a Umax scanner nor
could we take a Microtek TWAIN driver and make it work with an HP scanner. One thing
they all have in common is that they will all work with their prospective scanners and
software such as Adobe PhotoShop, Micrographfix Picture Publisher, U-Leads Photo Impact,
Omni Page, Xerox Text Bridge, Visioneer or any OCR & Image editing software that is
TWAIN compliant.
Now let's talk about what a TWAIN driver does. When you are in a program such as Adobe Photo Shop or Xerox Text Bridge, you will want to get to your scanner and get what's on it. You will usually use the "Acquire" function or (in Adobe PhotoShop's case) TWAIN 32 or TWAIN 16 selection under"file", - import. What happens here is that your software program calls up the TWAIN driver and the next thing you should see is you scanners twain driver program. This is where you will choose the DPI settings, mode settings (i.e. color, RGB, Line Art-Text, Gray Scale etc.) contrast, brightness, gamma correction, sharpness, descreening (for removing the dots in pre- printed material you will be scanning) pre-view, zoom in features and anything and everything that has to do with how you want this image or text to be delivered to the program you are using. The first thing you will want to do when your twain driver comes up is to do a "preview" of what it is that you placed on the scanning bed. Once the scanner delivers this preview image to the twain programs preview window, you will see what is that your about to scan. Choose either a portion or all of the image (or text) that you may want or need by dragging and dropping the outlined box in the preview window so that it in-circles either part or the entire image. You will then set the DPI and mode you wish to scan the final image at. Once you've completed all this you will click on the scan button and viola!, your image is now in the software program that you originally started from. Now you can do whatever you want to the image or text, your only limited to your software programs imagination.
Selecting the best twain driver for what type of scanning you will be doing is almost as important as the scanner itself. Some TWAIN drivers are very basic and some want to give you little or no control at all, we like the ones that have a wide range of options so that you don't have to do them all in your image editing software. Professional graphics people will always want a twain driver that allows them the most choices because they want to "be in control" of the delivered image and not have the scanners twain driver deprive them of making choices that they may want to be in charge of.
One cool feature a lot of scanner manufactures are including in their twain software drivers is called "batch scanning". What this feature does is allow you to place several items you wish to scan on the scanners bed and choose (individually) the DPI settings, mode, contrast, brightness, gamma, and once you have done this for all these items (and giving them a title) you can now click the scan button and it will go get them all! This is great for people who have multiple pictures they want to scan all at once and it saves time rather than scanning each image one at a time, separately.
OCR (Optical Character Recognition)
Optical Character Recognition is one of the coolest things a scanner can do and
what it basically means is that with a good OCR program such as Text Bridge or Omni Page,
you can scan a page of text right into Word or Word Perfect without having to re-type the
whole page yourself. This is done in the Line Art or Text mode and usually at about
300 DPI (depending on the size of the text). The scanners CCD's send the information
to the OCR software which in turn, deciphers the character (font) information and tries to
replicate it the best it can. No OCR program is 100%. Some scanners OCR better
right out of the chute than others, These are usually scanners that scan naturally
darker than others. If you have a great OCR software program but your text looks a
bit off, try upping the contrast to around +30% to +35%, you will find it gets much more
accurate.
The Scanners Bed Size
This is very simple. There are several different bed sizes (scanning area)
that scanners come in. Some bed sizes are legal (8" width and 14" length).
Some are 8" x 11" (A4 Size) and some are even as big as A3 size
12" X 18". One important thing to remember here is that if you are going
to get a bigger size than letter (8" x 11") than you might want to make sure it
is SCSI. Although there are some really impressive Parallel Port legal and A3
size beds, they can get really slow especially for bigger than average size color images.
A great parallel port model in an A3 size scanner is the Plustek A3-I . It does not come
with a transparency unit nor is their an option for one. Much more higher end models
such as the Umax Mirage II or the Microtek ScanMaker 9600XL have transparency adapters for
lager than average size transparency's. Both are SCSI and both are great
units. The Mirage has a nice dynamic range and resolution.
CIS Technology (Contact Image Sensor)
A new scanning technology has arrived on the seen and although there needs to be
some improvements made on it, it is swiftly becoming popular among scanner
enthusiasts whom wish to save space on there desktops at home or in the office. CIS
replaces CCD technology and what it does is eliminate the bigger and more space consuming
housing, mirror, lens and the cold cathode or fluorescent tube lamp, all of which are
needed for a CCD scanner. Instead of a lamp it uses a closely packed row of Red, Green and
Blue L.E.Ds to create white light. The sensors closeness to the glass and the original
image(or text) can be made as thin as a laptop, hence the space saving attributes.
Another bonus is since it uses LEDs, It uses very low power consumption which means that
they can run off battery's or a powered USB port.
One problem we have noticed with CIS scanners is that the image or text to be scanned must be totally flat (pressed) against the scanners glass, therefore making it a bad choice for someone wishing to do objects such as coins, jewelry or anything that may be lifted a little bit off the scanning glass (bed). Contact Image Sensor means just that, the scanners scanning sensors must make close contact with the item you will be scanning. At this time most CIS scanners are only 600 X 1200 but we are sure some higher resolution models are in the works.
Buying Tips
Well this ends the tutorial. We hope that this may help you understand some
of the questions you may have had on scanners. We here at The Scanner Outlet feel that an
educated buyer is always a better customer. So many times we have heard nightmare
stories from someone who thought they were getting a good deal only to find out they
didn't know what they were buying in the first place. That's why we thought (when we
started The Scanner Outlet) that we should be a master of our trade and not a jack of all
like other re-sellers. You make the decision, does it make sense to purchase from a
company who specializes in their field? Or, should you buy from someone who knows little
to nothing about the product they are putting in your hands? Like we said, we hope
your a better educated scanner buyer now. Never under buy, for you will pay for it ALL
again sooner than later. Never over-buy because a scanner is an awfully big coaster for
your beer!
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