Scan2CAD raster to vector conversion software

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What's the best scanner width for CAD?
Is DPI (resolution) a good way to evaluate large format scanners?
What's the best file format to save my scans in, TIFF, BMP or JPG?
I'm told that 48-bit colour capture is best. Is this true?
I want to scan and save PDF files. Is this possible?
Do I need an extended warranty option?
What are the benefits of leasing a large format scanner?
Can you recommend a scanning bureau?
I'm thinking of buying a Contex Hawk-Eye. Please advise?
How do I scan damaged or torn drawings without them snagging?
What is the best large format scanner for an Apple Mac?
I've got a Return to Factory Warranty but I've lost the box. Help!
Do you know of any scanners that can output DXF files?
What are the limitations on the length of a scanned drawing?

Q: What's the best scanner width for CAD?

A: A 36" image scan width fits all A0 and E size CAD applications.

The standard image scan widths on today's large format scanners are 36", 40", 42" and 44", although smaller A1 / D size scanners and super wide scanners up to 56" are also available.

A0 sheets (33" x 47") must be scanned in portrait mode on ALL these models. In other words, you get little or no extra benefit from the extra width if the maximum size of your drawings is A0.

E size sheets (34" x 44") must be scanned in portrait on 36", 40" and 42" models but can be scanned in landscape on 44" models. The advantage of scanning in landscape is that there is no need to rotate the drawing after scanning. Other possible advantages are that it may be marginally faster (no rotation required, less drawing length to scan) and that scanning drawings long side first means they are less likely to skew because they are being gripped by more rollers.

Super wide scanners such as the Colortrac SmartLF Gx+ 56 can scan A0 and E size sheets in landscape, but are much more expensive than standard width scanners.

Q: Is DPI (resolution) a good way to evaluate large format scanners?

A: DPI used to be an important factor to consider when buying a large format scanner because of low resolution scanners like the 200 dpi Contex Hawk-Eye.

The optimal scanning resolution for most CAD drawings is 200 to 400 dpi. If you buy a scanner with a low optical resolution like 200 dpi and you need to scan a drawing at 400 dpi or 600 dpi, the resolution will be interpolated and the quality will be less good.

However, all current large format scanner models have optical resolutions of at least 400 dpi, and most have 600 dpi optical resolution. 600 dpi should cover ALL your CAD, GIS or map scanning needs, so any scanner you buy today should meet your resolution needs - so long as it is a current model.

Image Access scanners offer 1200 x 600 dpi resolution. Colortrac Gx+, Contex XD and Contex SD scanners offer 1200 x 1200 dpi resolution.

Scanners4CAD believe that 1200 dpi is overkill for CAD and is not practical. For example, consider the size of an A0 / E size drawing scanned at 1200 dpi:

* Mono - 266 Mb
* Greyscale - 2.1 Gb
* Colour - 6.2 Gb

You are going to need a powerful PC to cope with those sizes!

Q: What's the best file format to save my scans in, TIFF, BMP or JPG?

A: We recommend TIFF files every time. There are several types of TIFF file. TIFF Group 4 is widely used for saving black and white images. Other TIFF file types can save colour. TIFF files are usually compressed. Because they are compressed they save disk space but unlike JPG files which are also compressed TIFF files don't lose data or quality during the compression process.

BMP (bitmap) is good because it does not lose file quality, but being an uncompressed format it creates very large files.

JPG files are the worst. When an image is saved as JPG its quality deteriorates. This can often be seen on CAD drawings as "clouds" or smudges around what should be clean, sharp drawing lines. In addition, JPG files are always colour files. If you save a black and white (2 colour) image as JPG, it will be converted to 16.7 million colours and your clean, sharp black lines will be converted into different colour shades with "clouds" or smudges around them.

If you are intending to convert your drawings to CAD using raster to vector conversion, DO NOT save them as JPG. The reduction in image quality may make accurate conversion impossible.

Q: I'm told that 48-bit colour capture is best. Is this true?

A: No, it's untrue that 48-bit colour capture is best. 36-bit colour capture is as good and if you are buying a scanner for scanning technical drawings it's irrelevant anyway!

While some large format scanners capture colour in 24-bit and output it as 24-bit, most scanners capture colour in 48-bit or 36-bit and output "the best" 24 bits as 24-bit.

To give you some idea of the numbers of colours we're talking about:

* 48-bit - 281475 billion colours
* 36-bit - 68.7 billion colours
* 24-bit - 16.7 million colours
* 8-bit - 256 colours

36-bit colour capture captures the entire range of colours that can be represented on the best quality scannable media (film transparency).

As 36-bit colour is capable of capturing all the colours that can be represented the additional colours captured using 48-bit colour add nothing to the range of colours that can be captured or used - they simply slow down the scanning process by piling in more data and creating bigger files to work with. And that takes time.

So, in conclusion, the statement which we think is most correct is "36-bit colour capture is best". It gives you all the benefits of 48-bit colour capture without the time and hassle involved in processing extra, useless information.

Why has this misconception occurred? Because bigger sounds better!

Q: I want to scan and save PDF files. Is this possible?

A: Yes, all the major scanners do this, but check whether scan to PDF is included free with the scanner you're intending to buy or whether you have to buy additional software.

Typically, people who want to scan and save to PDF want to email the drawing to someone. As result, the size of the PDF file is an important consideration. Be aware that some scanning software creates bigger PDF files than others.

For more information on scanning to PDF, click here.

Q: Do I need an extended warranty option?

A: In our experience scanners are generally reliable. The worst problems often occur during the shipping of the scanner to you. If this should happen, a good customer-oriented supplier should sort the problem out immediately regardless of the warranty option you have chosen.

As a general rule, we do not recommend you buy an extended warranty at the time of purchase unless you have a good reason to get one, for example you can't afford to be without your scanner for a few days.

The free two year RTF (Return to Factory/Base) warranty supplied with most scanners as standard is usually enough for most buyers. The downsides are that you must pay the costs of shipping the scanner to and from the factory should a problem occur and that you need to keep the scanner's (huge!) box, as most RTF warranties are invalid if the scanner is not shipped back to the factory in its original packaging.

Extended warranties usually offer a visit to your premises by an engineer or a swap out scanner (a replacement while yours is under repair).

The advantage of the swap out option is that a it usually costs less and lets you get on with scanning while your scanner is being fixed. Engineers who visit may not be able to visit next day, and when they do visit they may not be able to fix the problem immediately. With no fix, you do no scanning.

The disadvantage of the swap out option is that you still have the hassle of packing and unpacking your scanner and the replacement scanner, and as with an RTF warranty you may be required to keep the scanner's original box.

Q: What are the benefits of leasing a large format scanner?

A: The main benefit is that you get the use of a wide format scanner for relatively small, affordable monthly repayments. You avoid the very high cost of buying one up-front!

Besides minimal initial cash outlay there are other advantages to leasing equipment. Some depend on the type of leasing agreement you have.

Most importantly, leasing means that you won't have to increase your bank overdraft or place a strain on other credit facilities to get the use of a large format scanner now.

Leasing will allow you to use your cashflow for other, more vital business purposes while at the same time giving you powerful new but affordable equipment to increase your cashflow.

Depending on the type of leasing agreement you have you should be able to change an existing lease for another. This allows you to replace old equipment with new during the term of the lease. By giving you access to the latest technology a leasing agreement can ensure that you don't use obsolete, unproductive equipment.

At the end of some lease periods the scanner may become yours. Sometimes it can be purchased for a small fee. However, at the end of, say, a five year lease, the scanner may be worn and outdated. You may not want to buy it but would prefer to get a more reliable modern scanner to replace it. Leasing agreements can be made to do this.

The main terms of any leasing agreement should largely be determined by you, the customer. What scanner and accessories do you require? How much do you want to pay per month? (Remember, this is not about being poor, it's about using your cashflow sensibly). What flexibility do you have at the end of the leasing term?

Look for a service-oriented leasing company that will listen to your requirements and advise helpfully. There are many leasing companies who will compete for your business. Shop around for the deal that's good for you.

Finally, ask your accountant to confirm what the tax benefits of leasing are, if any.

Q: Can you recommend a scanning bureau?

A: Please click here for a list of scanning bureaus.

Be aware that scan quality varies enormously from one scanning bureau to the next. You may get good quality scans from one bureau and utterly useless scans from another.

In our general experience, the majority of scanning bureaus are more likely to give you a mediocre scan than a top quality scan suitable for archiving and or automatic raster to vector conversion.

Yes, there are good scanning bureaus. The best ones take time and pay attention to the individual detail of each drawing. For them there is no "one size fits all" scanning solution. Because they take greater care to provide you with a quality end product they generally charge more for their personalised services.

Of course, there are some who will charge you as much as they can whatever the quality of their work!

NOTE: Avoid scanning bureaus who quote low (in order to get the work) AND WHO ALSO promise fast turn-around times. They maximise their profit by scanning your job as fast as they can. Too fast in our view! Their priority is to "get it finished ASAP!".

Of course, you can stipulate a reasonable deadline to reduce some of the pressure on them to "bang out the work" but, in our experience, most of these operators will continue to do it as fast as they can because that's the business they're in - low-cost, high volume scanning.

Some scanning bureaus have little or no knowledge of CAD or raster to vector conversion. Few care about the finer intracacies of scanning.

If you are serious about scanning and preserving your legacy data for posterity or for raster to vector conversion, don't accept the first quote you get. Choose those who stress scan quality first and price second.

It is reasonable to expect that a sample scan will show you the quality of work you can expect to get. Unfortunately, this may be the only scan a dodgy operator will put any effort into getting right. Worse, they may also use the settings from this scan as the basis for the rest of your job, the assumption being that all your drawings are the same. They seldom are. On interrogation drawings have many differences between them!

On a big job the worst offenders will use the same pre-determined settings on every scan. They will not interrogate each scan to see if it can be improved in any way by adjusting the settings. They will automatically save each scan with an unhelpful, incrementally updated file name, like "scanarch01", "scanarch02", etc. What they don't see, you get!

Caveat emptor, CAD user!

A good quality scan will generally take longer and cost you more.

Q: I'm thinking of buying a Contex Hawk-Eye. Please advise?

A: We generally don't recommend the Contex Hawk-Eye (now obsolete) because we believe its optical resolution of 200 dpi is too low and too limiting.

Contex gave us the opportunity to evaluate the Hawk-Eye G36 in their head office in Alleroed, Denmark. We really hoped that they would show us that the Hawk-Eye is a suitable scanner for CAD.

However, while there are drawings where 200 dpi is all the resolution you need to capture all the drawing detail, our tests confirmed that the Hawk-Eye's maximum 200 dpi optical resolution is simply not enough for it to cover all CAD scanning situations adequately. For example, on the drawings we tested the Hawk-Eye's low optical resolution and resolving power was unable to separate some closely spaced parallel lines that other scanners are able to separate.

According to Contex the main case for using the Hawk-Eye in professional situations is where large numbers of wide format technical drawings and documents need to be scanned quickly at low resolutions for archiving and future viewing-only purposes.

Our advice, however, is that you are limiting your future options by archiving drawings at resolutions that are too low to allow conversion to CAD at a later stage. If raster to vector conversion is a possible future requirement and you want to buy a Contex, we recommend that you buy one of their better specified newer models capable of higher optical resolution, like the Contex SD series or the Contex HD4230.

Q: How do I scan damaged or torn drawings without them snagging?

A: The traditional solution is called sticky-tape. It provides a quick fix but is not an ideal solution.

A good alternative is to put the torn drawing into a plastic wallet also known as a document carrier sheet or a "skin". This provides a useful solution to the problem of scanning delicate or torn originals which cannot be taped prior to scanning.

Available to order with your scanner or separately these plastic scan wallets come in A1 / D and A0 / E sizes and are made from tough acetate or flexible polypropylene.

Scan quality is generally unaffected by the use of a plastic scan wallet, however despite the manufacturer's claims that they will resist scratching both polypropylene and acetate wallets will scratch with long use. This will ultimately have a negative impact on scan quality.

Q: What is the best large format scanner for an Apple Mac?

A: The are several options.

The Image Access WideTEK range is OS independent, i.e. it will run as comfortably on a Mac as on a Unix or PC system. It connects the Mac or PC to the scanner via a network cable and is run from a standard internet browser.

Contex scanners and their OEMs support the Mac via the Contex Photoshop plugin or via third party software options.

Neither Colortrac nor Graphtec scanners support the Mac. One possible and relatively cheap solution (although an anathema to most Mac users) is to buy a PC and connect it to a Colortrac or Graphtec scanner. Any scans created and saved can be read into Apple Mac applications. This suggestion is not as outrageous or as preposterous as it sounds. Many professional Mac users have PCs for situations exactly like this.

Q: I've got a Return to Factory Warranty but I've lost the box. Help!

A: There is little you can do except contact the factory and ask them if you can drive the scanner over to them securely protected with wrapping in the back of your car.

Under the terms of a Return to Factory Warranty you are usually required to return the scanner to the factory in the original packaging. This is to ensure that it is fully protected in transit to the factory and back again.

As scanner boxes are huge the temptation to destroy them is great. However if you return your scanner to the factory wrapped in bubble-wrap, blankets and brown paper it will probably get damaged en route and you will be liable.

In our experience many resellers do not advise their customer of the requirement to keep the box. Equally, most customers do not read the fine print of the terms and conditions of the warranty. Finally, the terms and conditions of the warranty itself often fail to highlight this very important requirement.

We have heard about a customer who bought a flatbed model of a leading brand of scanner. The box was destroyed in the unpacking. On start-up the scanner failed. The customer phoned the distributor who sent an engineer to examine the scanner. The engineer concluded that the scanner was repairable, not Dead on Arrival. Because it was repairable, the scanner had to go back to the factory to be fixed.

As the box was destroyed, it was impossible for the customer to return the scanner to the factory under the terms of the warranty. The customer was advised by the distributor that if they wanted the scanner repaired free under the terms of the warranty - it was that or not at all! - they had to buy a box from the distributor for £150.

Whilst we disapprove of this response to the customer's problem - we think that issues like this are not the customer's fault and should be quickly, sensitively and responsibly addressed by the manufacturer or distributor - these are the terms and conditions that come with the warranty when you buy a large format scanner.

Q: Do you know of any scanners that can output DXF files?

A: No, not one. No scanner creates DXF!

Scanning is a raster image process whereas CAD is a vector image process. The two are mutually exclusive.

The act of scanning breaks an image down into little squares, aka dots per inch (dpi) or pixels, basic raster elements. A scanned image is made up of hundreds of thousands of pixels. The higher the dpi, the greater the number of pixels. To get a DXF file from a scanned raster image you must use a raster to vector converter like Scan2CAD which will automatically convert the pixels into vectors (lines, arcs etc.) for editing in CAD.

Scan2CAD is a professional raster to vector converter. It is capable of generating more accurate vectors than similar programs but, like all other automatic raster to vector converters, Scan2CAD cannot achieve perfect results. Some tidying up in the CAD program will always be needed. If the combination of scanner and raster to vector conversion software is unacceptable, one alternative is to consider using a digitising tablet.

Q: What are the limitations on the length of a scanned drawing?

A: Large format scanners can physically scan drawings of any length.

In practise however the actual length of the drawing you can scan is limited by the size of the file in Mb that your PC is capable of accepting from the scanner.

The size of the file that will be created by the scanner depends on the resolution you are scanning at and whether you are scanning in mono, greyscale or 24-bit colour.

Scanning in mono at lower resolutions creates smaller files than scanning in colour at higher resolutions. Therefore, you will be able to scan longer drawings if you scan in mono at low resolutions. However, the resolution you use must be high enough to capture all the detail you need in the drawing, or the scan - although long - will be useless for your future purposes.

Let's say you scan an A0 / E size drawing. Here are the approximate sizes of the file you will get scanning at different resolutions and colour depths:

* Mono - 200 dpi: 7 Mb, 400 dpi: 30 Mb, 600 dpi: 67 Mb

* Greyscale - 200 dpi: 59 Mb, 400 dpi: 237 Mb, 600 dpi: 532 Mb

* Colour - 200 dpi: 177 Mb, 400 dpi: 710 Mb, 600 dpi: 1.6 Gb

Using a Pentium IV 3.4GHz PC with 1Gb RAM connected to the scanner by USB2, we were unable to scan an A0 / E size drawing in colour at 600 dpi with any scanner we tried except the Image Access WideTEK. The PC just hung.

The Image Access WideTEK contains its own powerful integrated onboard PC which allows it to scan larger images than scanners that are dependent on external PCs. However, even if you are able to scan very large images, you should consider the usability of the scanned files you create.

The size of the file in Mb might be so large that it is unwieldy to store or email and either impossible or very, very slow to open in an image editing program.

In addition, as well as Mb size, older versions of Windows could not handle images with a physical length greater than 32,000 pixels. This equates to the following drawing lengths (the same for mono, grayscale and colour images):

* At 200 dpi - 160" (13.3') or 4064mm (4.06m)

* At 400 dpi - 80" (6.7') or 2032mm (2.03m)

* At 600 dpi - 53.3" (4.4') or 1355mm (1.35m)

Although the 32,000 pixel restriction has now been lifted from Windows itself, it is still retained by many image editing programs. By creating images that are longer than 32,000 pixels you might be restricting what you can do with the image later.

So to conclude, yes there are limitations on the length of the drawing you can scan using a large format scanner. However these limitations are due to the current ability of PCs and software to handle large image sizes rather than due to the scanners themselves.