Author Archives: Jane

Digital Proofs vs Press Proofs

The printed proof is a dispassionate simulation of the ultimate output – a CMYK press sheet. The mission of a proofing system is to create accurate predictions, not pretty pictures. The primary goal of ‘proofing’ is to serve as a tool for customer verification that the entire job is accurate. Prepress proofing (also known as off-press proofing) is a cost-effective way of providing a visual copy without the expense of creating a Press Proof. If errors are found during the printing process on press, correcting them can prove very costly to one or both parties involved. A Contract Proof usually serves as an agreement between customer and printer and as a color reference guide for adjusting the press before the final press run. Most contract proofs are a Prepress Proof.

Digital Proofs and Press Proofs

There are mainly 2 types of proofs, the digital proofs and the press proofs.

The press proofs, also called wet proofs is the most accurate and costly proofs both for four color and pantone color jobs. Wet proofs use the exact paper and inks to be used in the final job and therefore give an exact representation of the finished job. It requires special set-up on press and special plate output which makes it a pricier proofing option. However, this type of proofing process yields the best color proofing result. Wet-Proof is an option especially recommended on projects that are critical on colors. This includes art books; museum quality projects and photography books.

The digital proof, sometimes also called color proof, provides the color-reliable/color-true reproduction of the contents of the file intended for printing. Color proof is made with inkjet printers or thermal sublimation printers in combination with powerful color-management systems. Proofing is usually performed in full-size format, but in some cases small-page format is also acceptable. Color proof serves as a guideline for a printing press operator, and usually stands for a contract proof.

Below is the comparison of the digital proofs and the wet proofs.

Digital Proofs vs. Wet Proofs:

Advantages of Digital Proofs

The cost to output digital proofs is more competitive compared with wet proofs if only one set of proofs is required.

Preparing digital proofs are faster than preparing wet proofs.

There are fewer problems with dirt, spots, or registration problems which are common in wet proofing.

Translating Digital proofs to Printed sheets: digital proofs are warmer than wet proofs because of the nature of chemical ink–it is different from actual printing ink. The color tolerance between digital proofs against the press sheet is about 10% to 15%.
Digital proofs are the fastest to output (it takes about thirty minutes to output eight pages of an A4 size).

Disadvantages of Digital Proofs

Digital proofs do not reveal problems in the files, such as trapping, overprints, or moirés.
The tint colors in digital proofs cannot be matched during actual printing.
PMS colors are not accurate in digital proofing as it is in wet proofing.
Digital proofs are not suitable for black and white images, duotone, or 4-color black and white images.
Lineart or rules will be thicker than actual size due to distortion.
Digital proofs are printed on digital paper so the color will be slightly different because is not on the “actual” paper.

Advantages of Wet proofs from CTP Plates

The cost to output wet proofs is more economical if several sets of proofs are needed.
The color is more accurate for black and white, duotone, and 4-color black and white images or for PMS colors.
Problems in the files will be apparent, such as trapping, overprints, and or moirés.
Wet proofs use the same paper type and weight as it will be used during manufacturing.

Disadvantages of Wet proofs from CTP Plates

Wet proofs take longer to prepare than digital proofs.
Dirt, spots, and registration problems cannot be avoided.
The cost of outputting wet proofs is high if only one or two sets of proofs are needed.

Halftone

In the color printing, ink of only 4 colors are used, which are cyan, magenta, yellow and key(black). When CMY “primaries” are combined at full strength, the resulting “secondary” mixtures are red, green, and blue. Mixing all three gives an imperfect black. And for each color, it has infinite shades and tones. (learn more here about the color basics, hues, tones, shades and tines).

CMYK color                                                CYMK subtractive color

The problem here is that how can we simulate the different shades, like pink color,  of a color with the only the magenta color ?

In the 19th century, the graphic designers find that the discrete dots, varying either in size, in shaping or in space can used to generate a gradient like effect. And this reprographic technique is called halftone.

Check the picture below for a better and clear understanding:

Left: Halftone dots. Right: How the human eye would see this sort of arrangement from a sufficient distance.

halftone explaination

File Format For Print

1. Native file format — acceptable print format for printers

When preparing pages for printing, the graphic designers generally use page layout programs to provide the structure and design for the job. Page layout files include the overall page design elements (rules, columns, screen tints, and so on) as well as text. These files, also known as native files, vary in format from one program to another and generally do not contain photo or illustration files. Instead, graphic files are linked to the page layout file. In addition, page layout files do not contain the fonts used to display and output the typefaces used in the document. Thus, jobs delivered by the designer to the printing company or other service provider in the native format must be accompanied by both the fonts and image files. Page layout programs provide a method to “collect” or “package” the supporting files that must accompany a native page layout file in order for that file to output properly.

.psd is the native file format for the Adobe Photoshop, .ai for Illustrator, .indd for InDesign.

EPS (short for Encapsulated PostScript) is a vector format designed for printing to PostScript printers and imagesetters. It is considered the best choice of graphics format for high resolution printing of illustrations. EPS files are created and edited in illustration programs such as Adobe Illustrator or CorelDRAW.

Vector graphics are a scalable, resolution-independent format composed of individual objects or shapes. Vector images can be resized easily without loss of quality making them an ideal format for initial logo designs and illustrations to be used in multiple sizes.

2. Recommended file format (PDF)— stardard print format by SWOP

PDF/X1a is the most widely adopted, all-inclusive file format relevant to the printing industry based on the Adobe’s Acrobat PDF format. The printing layouts created in the Adobe Photoshop, Illustrator and InDesign all can be saved in the PDF format.

TIFF/IT-P1 is an internationally-accepted format accredited by the International Standards Organization and known as ISO 12639:2004. “ISO 12639:2004 specifies a media-independent means for prepress electronic data exchange using a tag image file format (TIFF). ISO 12639:2004 defines image file formats for encoding colour continuous-tone picture images, colour line-art images, high-resolution continuoustone images, monochrome continuous-tone picture images, binary picture images, binary line-art images, screened data, and images of composite final pages” (International Standards Organization, 2004).

PDF verse TIFF

Although SWOP allows designers to save files in either format, a review of the specifications pages for numerous publications reveals that the trend is toward PDF/X1a and away from TIFF/IT-P1.

3. Web image format (JPEGs, PNG, GIF) — the least wanted file format

JPG (short for Joint Photographic Experts Group, and pronounced jay-peg) is a file format best used for photo images which must be very small files, for example, for web sites or for email. JPG uses lossy compression (lossy meaning “with losses to quality”). Lossy means that some image quality is lost when the JPG data is compressed and saved, and this quality can never be recovered.

GIF (short for Graphics Interchange Format) is a file format for storing graphical images up to 256 colors. It uses a lossless compression method which makes for higher quality output.

PNG (short for Portable Network Graphics) was created as a more powerful alternative to the GIF file format. PNGs are not restricted to the 256 color limitation of GIF files and have better compression. A PNG file can be saved with a transparent background which allows you to place your image on top of another image without an outlining white box.

GIF files are probably the most popular on the web being used in logos and color images. Even though PNG files are widely supported, GIF is still the most popular.

TIFF, JPEGs and PSD

TIFFs, JPEGs and even PSDs are what you should be saving your bitmap files as (the sort of things created in Photoshop).

TIFFs and PSDs are lossless. You don’t lose any quality by saving a file as a TIFF or PSD.

JPEGs normally lose quality when you save them but take up a lot less space on your computer. A very high quality JPEG is often not a lot different to a TIFF or PSD, but it does very much depend on the sort of image you’re saving.

A TIFF or PSD is normally a better option than a JPEG. But if you’ve been supplied with a JPEG, from a camera or stock photo website, and you’re not modifying the image then you will gain nothing from saving it as a TIFF or PSD. A TIFF or PSD cannot create detail where there was none in the first place. But a JPEG can remove detail where once there was some.

There’s a couple of thing to notice in the pictures here related to JPEGs. Firstly, JPEGs can’t handle spot colours. So when this JPEG was saved it converted the Pantone colour into a CMYK value. Secondly, the white space in between the red lines on the JPEG is filled with a very subtle yellow/grey tint. This is due to the compression.