Prepress preparation of layouts

Before sending the layouts to print, it would be nice to make sure that the result will be worthy, and to do this, it is enough to go over a small check sheet and correct all the flaws that he revealed. So, the checklist for pre-press layout:

1. Translate all files to CMYK color format

The RGB color model is based on the fact that each pixel on the screen emits its own light, but the paper cannot do this, so the RGB files printed on it will be dark. To avoid this, the files are converted to CMYK format. With it, a full-color image is formed by mixing colors: cyan (cyan), magenta (magenta), yellow (yellow), key (usually black).

More information about the selection of colors in the article "Colors for printing, select" Pure "CMYK colors."

2. Make sure that the colors used do not exceed 280-300% in total

The selection of colors for printing is not the easiest thing, here you should take into account many features. The most vivid example of one of them: paper is of different density. Most commonly used in print:

Writing paper from the printer has a density of 70 g / m2.
leaflets, flyers, and menus are printed on paper 110-150 g / m2.
business cards, covers, packaging up to 300 g / m2.
Accordingly, paper with different densities absorbs ink differently, and the results on printing turn out to be different. If there is little ink on thick paper - the colors turn out to be pale, if there is a lot of ink on thin paper - the color will leak onto the back side of the sheet, which is especially unpleasant when duplex printing.

Glossy and matte surfaces also behave differently with paint.

If you do not take into account all these factors, it is likely to get a joint in the final product. To avoid unpleasant consequences, colors in the layout are selected on the basis of the indicated factors, and most often converge in the rule that the sum of colors (the sum of CMYK indicators) should not exceed 280-300% (in rare cases, 320%).

And also, choosing colors it would be good not to forget that the more colors a paint describes, the darker it will end up.

More information about the selection of colors in the article "Colors for printing, select" Pure "CMYK colors."

3. Set the file with the layout resolution at 300dpi

An important parameter when printing is the image resolution, it is measured in the number of pixels (dpi) or points (PPI) per inch. According to research, the human eye is not able to distinguish pixelation above 300 dpi (at lower values ​​on professional prints pixels will be clearly visible), and higher values ​​are impractical.

Statistics of using different dpi:

for industrial printing all images should be 300 dots per inch (dpi);
for a domestic printer come down 100-150 dpi;
for large format printing, which the viewer will admire from a distance of at least a meter. or even two 90-120 dpi;
for 72 PPI screens - for the eyes and for the ears.
Life hacking: How to find out how many dpi (actually PPI) in the picture? Measure the length and width of the layout in centimeters, multiply each value by 118 (for 300 dpi) and get the desired size in pixels.

21 x 29.7 cm = 2478 x 3505 pixels

4. Make sure that the necessary graphic elements are presented in the vector.

Small elements presented in the form of graphics risk to be smeared and fuzzy.

5. Convert all fonts to curves and embed images into a file.

It’s not at all the fact that in the printing house where you are going to print the file, the font used in the layout will be installed. You can, of course, transfer them along with the layout, or embed it in a pdf file, but it is much easier to translate it into curves.

And don't forget about the images, all the images used in the layout must either be attached to the layout or embedded in it.

6. Make sure that the correct paper size is set in the layout that matches the final format.

The scale of the layout should be 1 to 1 equal to the size of the final product, but add flights to itself (that is, A4 leaflet is 210x297 mm and 3 mm each in total 216x303 mm).

7. Bring all images to the size of the printed product.

If the pictures in a multipage edition were originally made larger or smaller than planned in the layout, and then decreased or increased in Illustrator or inDisign, then in the end, either the PDF size is put indecently huge, or the image quality in the product leaves much to be desired. Of course, this item will not interfere with the printing of budget or short-run products, but if you plan to store the layout for later reuse, then why not put it in order?

If you use TIFF files, it is advisable to use the LZW corporation.

8. Check availability of departures and indents.

Large-circulation printed products are cut into piles, and the knife tends to deviate, within the margin of error, therefore space should be provided in the layout that will allow avoiding incorrectly trimmed fragments. This space should be a continuation of the image, and not a white frame around the layout unless of course a white frame is provided in the layout around the composition. Departures are usually made from 3 to 5 mm.

If printed materials are cut one by one (billboards, signs, etc.), then this item can be skipped.

In addition to departures, it is good practice to indent text and important parts from the edge of the page, which should be at least 5 mm.

9. Check black color

As a rule, deep black can be achieved using C 25 / M 20 / Y20 / K100. In any case, the composition of black should include 100% of black, and the rest of the colors — at your discretion, but not exceeding the established rate of 2 points — 280-300%.

10. Check gray

Gray color can be obtained in two ways.

First way: take black gradations and set the desired value, for example, C: 0 M: 0 Y: 0 K: 50.

Second way: mix yellow, purple and cyan in a certain proportion. For example with 50% black, this is C: 47 M: 37 Y: 37 K: 0.

In theory, in both cases the same gray color of medium saturation should turn out, but, in practice, the second way will lead to an imbalance — an unpredictable stall into a warm or cold shade of gray. Moreover, printing defects will be the more noticeable, the lighter the shade of gray.

11. Uniform fill

On uniform fillings, a whole bunch of problems is often noticeable: spotting, different shades, moire, bubbling, longitudinal or transverse rinsing (when stripes of different tonality are noticeable). So that such defects are not conspicuous, you can add noise, gradients and other “decorations” to the homogeneous area, but if you need the exact color of a uniform fill, it is advisable to print it with “Pantone”. Pantone blend paints are prepared in advance at the paint mixing stations, according to the number of the special catalog. They come to the printing house in finished form, which eliminates the occurrence of an error in obtaining color, as happens when mixing four colors.

12. Transform effects

For the best quality of the final output, all the effects created in the layout, such as shadows or gradients, need to be converted to a raster.

13. Fit color profile

Ideally, you should ask the printing house for information about the color profile used. This is necessary because each printing device "understands" the color differently. Most often in Russia for offset printing:

on coated paper with a density of 100-150 g / m used profile Coated FOGRA39 (ISO Coated v2)
for papers with a density up to 100 g / m - ISO Coated v2 300% (ECI) profile

14. Overprint and Tremping

When offset printing, black objects should be placed on top. This rule has increasingly begun to be forgotten. Why and why? Look at the diagram of how the offset printing looks like:

In order to carry out printing, paints in printing houses are “smeared” on sheets (or cylinders) and these sheets make an imprint on paper. Under the elements of a different color left white space, so that the paint could lie on the white paper. And if a sheet of light ink lies on top of an already printed dark one, such an unpleasant effect can be observed, when the paint does not fall on a fraction of a millimeter and leaves part of the sheet unsealed. If the black ink will be printed last, the “white space” for another color will not be envisaged in the plate below, the background will lie in an even layer. In order for the black elements to be printed last, it is worth applying the “overprint” property to them.

If at first the whole area is sealed with light paint, and then dark, there will be no gaps, and the black color will be juicier.

To combat the similar effect of color inconsistencies, resulting in printing products with large fields of color, trapping is done. Trapping is a small allowance (stroke) in places of overlapping colors on each other. If trapping is correctly done in the layout, the colors are almost indistinguishable, and the likelihood of a gap (an unprinted area) between colors is reduced to zero.

Roughly speaking, not to get like this:

It is necessary to do this:

As a rule for printing small products, there is enough trapping at 0.25pt, for printing large formats - 0.5pt. But it is better to clarify this information with the printing house.

15. Features of multipage editions

When preparing multipage editions, errors of cutting, creasing (when a groove guide for folding is pressed between sheets) and folding (an operation to assemble sheets in a notebook) usually arise due to a misalignment of the left and right sides of the spread. This can be an unpleasant moment if there are images in the layout that are transferred from one part of the reversal to another. If in the printing house such an error goes beyond the limits of the norm, then it is probably worth refusing such a move or changing the printing house.

For the same reason, it is better not to bring texts or meaningful images closer to the fold point less than 15 mm, otherwise, the perception of the text may be difficult.

As for the norm, then you can refer to the GOST, which states that: “the allowable combination of folds in the finished notebooks on papers weighing 100 g / sq. m and above is 1.2 mm. "

Color proof and test printout

And, of course, even after you were convinced that all necessary points were observed, you should not ignore the need to make a printout of the prototype. It will help identify unsuccessful features of the layout.