Common Large-format Jargon

April 12th, 2012

Do you speak our language?

by Dave Winfield

Here is a list of common Large-format printing terms that frequently require a little extra clarification and consideration when producing printed digital graphics.

1) PDF – stands for Portal Document File, and was created by Adobe Systems, Inc. This file format creates a stand-alone document, which includes vector, bitmap and font information in an all-inclusive compressed file. The caveat to using this format is that it is not easily modifiable if changes need to be made. With new PDF editing software, and basic editing tools, we are more willing to except this file format for printing as long as you consider the following.

a. Bleed. Make sure that enough bleed is provided for our finishing requirements.

b. Color space and transparency. PDF will give unexpected results if you mix different color spaces and transparency effects.

c. White ink. If using white ink in the printing process, a spot white ink layer must be set up in the file. As well, trapping of the spot white ink layer should be employed.

d. In all of these cases, if you are unsure how to employ any of these techniques, please call ahead for some consulting, or simply supply an unflattened working file. We will gladly set up the file correctly.

2) Color space – refers to RGB, CMYK, or LAB settings of a computer display. These settings are translated via calibration tables at the printer RIP station to output a graphic from the printer that is close to what you may see on a similarly calibrated computer display.

a. We are a certified G7 printer which means we went through an intensive training, and certification process to insure our printers and digital processes are all in calibration. This calibration is employed daily to insure color consistency across our different printing platforms.

b. To insure you get the expected color results from our printers, start by creating your digital graphic files using either Adobe RGB, or CMYK GraCol_2006 Coated color spaces. This includes, vector files, and bitmap files. It is UNADVISABLE to mix these formats; Use either, or. By standardizing, you will avoid unexpected digital artifacts that are created in mixed color space environments, and you are starting from a common color space that we employ.

c. We do NOT rely on our computer displays to judge what we get out of our printers. Instead, we make sure proper color spaces are used and produce color print proofs on calibrated proofers. Then we view those in a color accurate proofing booth. This is the best way to truly see what to expect for a final print. Every computer display is different, and every lighting environment is different so we use a controlled environment to standardize our proofing process.

3) Second Surface – refers to which side a graphic will be viewed when mounted to a transparent substrate. Imagine a piece of glass on a table. Now place a piece of paper on top of it; this is considered first surface. If you place the piece of paper underneath the glass, it would be considered second surface.

a. Second surface is used for mounting graphics to the “backside” of Plexiglas, or window glass. It is generally a safer application because it removes the ability for the public to “pick” at the graphic.

b. When performed properly, second surface mounting produces stunning results.

c. Considerations when using second surface mounting are:

i. Imperfections in the Plexiglas or window glass will be visible, i.e. bubbles or imperfections in the glass or Plexiglas, or trapped air and/or particles between the surface and the graphic.

ii. It is a more difficult mounting procedure and is therefore more expensive.

iii. An optically clear adhesive has to be mounted to the face of a graphic or a clear adhesive vinyl that is “reverse” printed needs to be used.

4) Contour – refers to a cut shape. Graphics that need a cut shape other than squared off corners are easily producible with our digital cutter. Within your vector graphics program, create a layer named “contour”. Create a “spot” color on your color palette called “contour”. The color can be any color, as long as it is a “spot” and is named “contour”. Then, draw the shape of the cut you want to be produced on the layer “contour”, using the “contour” color. That’s it.

a. Our rip will know this layer is to be used for cutting and not printing. It will produce a set of registration dots that our cutter will use for final cutting.

b. Considerations when creating contours are:

i. Tightness of contours. Our digital cutter can cut any angle in amazingly small increments of space, but substrates have limits to how much they can be cut. Too tight of turns on rigid substrates will tear them. Tiny indentations can create odd points that will never be missed by the human eye if left out, but may damage the final piece and become noticeable.

ii. Routing of rigid materials. Substrates like Sintra, Plexiglas, Wood, and Diebond need to use a router bit. We have many sizes of router bits; the smallest is 3mm (approx. 1/8”) wide. Imagine a line that represents the path you want cut. If the 3mm bit follows that line down the center, it will remove a 1.5 mm of material off both sides of that path. To compensate the router will “offset” the bit to the outside or inside of the line, depending, and no extra material will be removed. However, if your indentations and curves in the contour are narrower than 3mm, the bit will cut out areas you do not want it to cut out. Therefore, you need to simplify your cut path so you avoid these unexpected issues.

iii. Using router bits, on inside corners. Looking at a capitol letter “D”. The interior cut of the “D” has 2 “sharp” corners. With a router bit, those corners will have a small round shape the same size as the router bit. To get around this, a softer rigid substrate may need to be used for cutting so the knife blade can be employed, or the inner corners could be filed sharp for an extra finishing charge. But more realistically, due to viewing distance and “read-through”, the general public will not notice the slight roundness of the edges and your message will be understood without distraction.

5) Pole Pocket – refers to an area on a banner that is created to accommodate a pole for hanging and/or for creating structural rigidity.

a. Considerations for creating pole pockets.

i. Safety Zone. The Safety Zone is an area on a graphic where critical information like logos, headlines, or text should NOT appear to avoid the pole pocket area. If critical information is placed in or near these areas, readability may be affected do to sew lines, the roundness of the pole itself, or pole pocket edge alignment. It is important to place important information at least 1″ away from these areas.

ii. Creating the Safety Zone. Using the number π (3.14) times the diameter of the pole, then adding 1″ extra, will give you the size of Safety Zone you need. For example, 3.14 x 1” (pole diameter) + 1″ = 4.14”. Draw a guide down from the top of your banner at this dimension. This is the top Safety Zone. The same can be used for a bottom Safety Zone. On the sides, It is a good idea to use at least an 1″ as a standard Safety Zone.

6) Resolution – refers to the pixels per inch (ppi) your bitmap images are created at, and/or the dots per inch (dpi) our printers can produce output. Resolution can be confusing, but if you follow the simple rules noted below, you will be able to expect an excellent print from our printers.

a. Here are our minimums for Photographic Lambda prints.

i. If using our Lambda, your minimum resolution for your images is 100 ppi at final size. If you place your scanned image in your layout at 100% size, and the layout file is created at 100%, then your effective resolution will be 100 ppi.

1. Good Example; You have a layout file of 12” x 12”. You place a tif file that is 12” x 12” at 100 ppi. You will get excellent results when printing on our Lambda printer.

2. Poor Example. You have a layout file that is 12” x 12”, and you have a tif file that is 3” x 3” at 100 ppi. In the layout file, you enlarge the tif file to 12” x 12” to fill the entire page. Your output will only be 25 ppi at final size, you will get a very pixelated image when printed.

b. Here are the minimums for Inkjet prints.

i. If using our large-format inkjets printers, it is a little more complicated. Depending on viewing distance, your resolution can vary from 30 ppi used on billboard sized banners, to 90 ppi on POP displays. Generally, we prefer to use 90 ppi at final size as a minimum. Same consideration applies when working at scale.

c. Determining resolution at scale – examples.

i. Desired output 100 ppi, working scale 25%, required resolution is 400 ppi if image is placed at 100% of created size.

ii. Desired output 90 ppi, working scale 50%, required resolution is 180 ppi if image is placed at 100% of created size.

iii. Desired output 30 ppi, working at 10%, required resolution is 300 ppi if image is placed at 100% of created size.

d. Maximum Resolutions.

i. Photographic – 200 ppi max. for images and normal sized text, 400 ppi max. for very small text (6pt) and lines (.5pt or smaller).

ii. Inkjet – 180 ppi max. for all applications.

**Resolution for Vector graphics is not a consideration. Vector graphics will be “ripped” at the resolution the printer requires when we print files. Example, if your printer prints at 360 dpi, your vector graphic will be produced at 360 dpi.

7) Res-ing UP – “Res” stands for resolution and refers to taking a bitmap image file and adding resolution to the file. An image that has too low of a resolution will look pixelated and have jagged edges. To avoid this situation, an image needs to be “res”ed-up.

a. Considerations when “Res”-ing up images.

i. Start with the highest possible resolution scan that you can have produced for an image. The more initial data an image has when enlarging the image, the better the detail of the image after “Res”-ing up is done.

ii. Images that are “res”ed-up will become softer when viewed. Software used for “res”ing-up, i.e. Photoshop, or Genuine Fractals, analyze an image and add pixels logically using algorithms that only computer scientists can explain. The best outcomes are “soft” images. But, when you account for viewing distances of a large graphic, it usually does not matter and the results can be spectacular.

iii. Imperfections are more visible. In the scanning process, dust and scratches on the original art, or imprecise Photoshop cloning may, at small size, be unnoticeable. When you res-up and enlarge the image, these flaws become much larger and may become very noticeable. It is always advisable to carefully inspect your images for these types flaws before you submit your art for printing.

iiii. Photo grain and jpeg noise.

1. All photographic film, at microscopic scale has a grain to the color layers. Grain looks just like it is described, colorful sand. When viewing from a distance, this grain is not visible to the human eye. When you enlarge the image, it becomes more and more visible.

2. With digital cameras, you may see a “jpeg” noise on the images. It looks like odd areas of color that surround good areas of color. This “noise” is created by the compression applied to the image file when the images are saved on a digital device. It is usually not very visible at small size, however, when it is blown up it becomes more noticeable.

In both instances, undesirable grain or noise can be minimized using image blurring techniques, if done carefully.