Frequently Asked Questions

Scanner Imaging Technology

CCD Imaging (Charged Coupled Device): 
This method of scanning involves capturing images through the use of a series of cameras that are spread out across the scanning area. These scanning systems use a fluorescent light source and a series of mirrors to reflect light from the surface of the document and pass it to the camera array. The number of cameras will vary depending on brand, model, and scanner width. These systems are also very sensitive, and require calibration from time to time as atmospheric and environmental factors can throw the camera alignment off. The main calibration that needs to be performed is a stitching calibration which aligns the areas where camera fields intersect. Color and white point calibrations generally required for these scanners as well.

CIS Imaging (Contact Image Sensor):
This method of scanning involves capturing images through the use of light reflected off of the surface of the document on to a silicone light sensing array. The silicone sensors are divided into individual sensing cells, and the size and density of these cells determines the optical DPI of the Scanner. The illumination for these Scanners is produced by Light Emitting Diodes (LED) pulses that are directed along surface of the document, and then on to the sensor. Color CIS sensing is produced by rapidly pulsing red, green and blue LEDs. Because there is no color filter used, the color gamut (range of the color spectrum that the scanner can capture), is generally somewhat less than that of a CCD scanner. One big advantage to these Scanners is that they do not require a warm up period like CCD scanners do.  

Which Technology is right for me?
This question is somewhat dependent upon the application that the scanner is being used for. A good way to make this determination is whether you need to capture color at a high resolution and with a wide and highly accurate color gamut. If you really need high end graphics resolution, then a CCD Scanner is what you should be looking at. If you primarily scan line drawings, blueprints, or any other document that does not require high end graphics resolution, then you may want to consider a CIS Scanner. CIS Scanners require less calibration, will maintain calibration longer, are very effective and accurate machines for most scanning applications.
Dots Per Inch (DPI)

What is DPI?

Dots per inch (DPI) is a measure of the resolution of a scan or print. In other words, it is a measure of a scanner or printer's accuracy based upon how many individual dots can be read, or printed within a one square inch area. There are two main ways that DPI is used in the industry, and the difference between them can be very important. There are other considerations that weigh into a machine's DPI capabilities such as scan/print speed, and other various driver settings. Optical DPI (or true DPI) is a measurement of how many dots per inch a scanner/printer is capable of handling without digitally changing the scan and/or print.

Optical DPI:

Optical DPI is generally considered to be the most accurate measurement of a scanner or printer's capabilities. Most large format scanners and printers will have a DPI range from 96 up to 600 DPI.

Interpolated DPI:

Interpolated DPI is a measurement that refers to images that have been re-sized. When an image that is 600 optical DPI is blown up, the DPI needs to be interpolated by software in order for the image to retain integrity. This means that the software will expand the image, and then go through the image and fill in the white space that is created between the dots when the image is expanded. Interpolated images, while a good concept in principle, lack the accuracy and definition of non interpolated images. Interpolated DPI is often what manufacturers list as the product's DPI in order to make the product appear more capable than it really is. If you are unsure as to which DPI information you are looking at for a particular product, we can help you accurately assess the machine's capabilities.

DPI and Scanning Speed:

Scanners usually list the speed capabilities of the machine in their sales materials. Generally, scans that are conducted at higher speeds will see a reduction in resolution quality. However, this does not mean that using the slowest setting will necessarily give you the best possible result. Most scanners will have an optimal threshold that will produce quality scans. We are happy to make recommendations as to optimal operational parameters based upon the scanner, scanning technology, and documents being scanned. Generally, the best way to determine the proper settings for your scanning needs is through trial and error.

Tips for Scanning and Printing at Optimal DPI:

  • Avoid interpolating the DPI.
  • Scan at a lower speed when scanning.
  • Bring your white and black points in a little.
Scanner Rental Information

contex iq 2490 quattro

Large Document Solutions is one of the few companies in the United States that rent large format scanners. To be successful renting scanners, we rent the best scanners available on the market. The characteristics of these scanners include: the most functional software, ease of use, ease of setup, and most important very durable. We rent 42” Contact Image Sensor (CIS) color and monochrome scanners because these are the most flexible scanners for the rental market. Our rental price includes shipping round trip.

Every scanner is thoroughly checked out before it goes out on a rental:
  • The document hold-down unit and image sensors are checked and adjusted, then tested and re-tested.
  • The paper sensors are tested to make sure the scanner is in excellent working order.
  • The glass is examined and cleaned.

Some of the scanners we rent are out for up to 6 months at a time. During those rental periods, the scanner could scan 35,000 to 50,000 documents of any size, shape, and material. Customers use our scanners to scan mylar and paper, old and new. Mylar is a very abrasive material to scanner glass. Before we send a scanner out for rental, we clean the glass with a fine razor then with our own glass cleaner exclusively used for scanner glass. After all the repair and adjustments are complete, the scanner is calibrated. Calibrating your scanner insures the scanner scans what you see on-screen and what you print are all the same.

For more information, please visit our Rental Page.

Protecting Fragile Documents

Carrier sheets are a great way to protect your documents when using a large format rollfed scanner. White-backed sheets are best for most applications and to reduce light reflection. Black-backed sheets are for specialized applications, including template scanning and tracing patterns for the apparel and upholstery markets, as well as semi-transparent originals printed on both sides (such as newspapers and double-sided maps) –  to prevent backside image appearing in the frontside scan.

Benefits of carrier sheets:

  • Protect fragile, dry, aging and valuable materials.
  • Protect scanner glass from documents contaminated with storage debris and dust.
  • Scan documents in badly torn condition or with missing edges.
  • Scan lightweight or oddly shaped originals, including upholstery patterns.
  • Scan transparencies more effectively and minimize light reflection.

Depending on the condition of the documents being scanned, each carrier sheet can last for hundreds to thousands of scans before it should be replaced. To extend the life of your carrier sheets, you can apply a product called Rain-X - with a new formula designed to be used with plastic. Normally this is done to protect glass from wear and tear, but it also works great for scratched carrier sheets. 

Please visit our Carrier Sheet page to place an order.

Plotter Inks and Toners

Pigment Inks, Dye Based Inks & Dry Toners:

When shopping for a plotter, the question of which types of ink are appropriate for your application is one that can be confusing, and is often a deciding factor in which machine to purchase. There are a few main factors that should be considered when looking at plotters.

Essentially, there are three main options that we offer in plotters that should be taken into consideration; pigmented inks, dye based inks, and LED based printing technology.

LED Printing:

LED (Light Emitting Diode) technology can be a very effective method of printing for black and white applications. LED printing is similar to laser printing in that light is projected on to an electrostatic drum, thereby allowing toner to be attached to the drum in the areas that have been charged by the light emission. The toner is then transferred from the drum to the paper where it is pressed and heated in order to bond it to the paper. LED printers tend to be very effective for black and white renderings, and tend to have great longevity. There is only one toner to deal with, and no print heads that can clog and need to be replaced.

Dye Based Inks: 

Dye inks are just what they sound like, ink that dyes the paper or other medium. The potential advantage of these inks is that the end result gives a smoother surface layer on the medium which will result in a more even light refraction. This in turn can, in theory, deliver more consistent color interpretation. This theory does not, however, take into account the light refraction properties of the surface of the paper or other medium. The potential disadvantage of these inks is the bleeding of one color into another as the wet ink is laid into the paper.

Pigmented Inks:

A simple description of a pigmented ink would be crushing a berry and using the crushed pulp to color a medium. These inks have come a long way since the days of cave paintings. Canon's current line of pigmented inks have a smaller drop size than that of the competition's dye based ink. Additionally, the Canon Pigment inks have been chemically formulated to prevent the different inks from mixing, so that there is no bleeding of one ink into another. This allows for precise printing of one color over another. The potential disadvantage of these inks is that the pigment particles, as they dry, leave a slightly rough surface, that affects the light refraction properties of the ink, which can effect color interpretation. However, the roughness of the surface of the ink can be effected in different ways by the surface properties of the printing medium, and in our experience has shown no noticeable adverse effects in regards to color interpretation.

Ink Longevity:       

There have been numerous tests performed on the longevity of dye vs. pigmented inks. Most of the data points to pigmented inks as being able to last longer than dye based inks. There are many factors that play into this. Under artificial lighting conditions, the two inks generally perform similarly, but under natural light, tests have shown that pigmented inks do generally hold up better. The tests suggest that the time range that these inks will withstand light depredation is in the range of 80 to 100 years. If you desire greater longevity for your plots, there are spray sealants that can extend the life of your plots.

Do Print Heads clog faster when using pigmented inks?

There is no evidence to suggest that print heads will clog faster when using pigmented inks as opposed to dye based inks. With Inkjet printers, the inks are distributed through print heads that have thousands of tiny holes, or jets in as little as a couple square inch area. With both dye and pigment based inks, the ink is suspended in a liquid medium that evaporates away, leaving the dry ink on the paper. After printing, ink that remains in the jets can dry, and clog the jets. The technology is designed so that when new ink enters the print head, that the dry ink in the jets can be re-dissolved in the suspension medium, thus clearing the jets. The best way to prevent clogged print heads is to print regularly. When a print head is stagnant for too long, the ink in the jets can dry to a point that it can not be entirely re-absorbed into the print medium, thus clogging the print head.