Printing in color: Practical & Technical guide

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Hello everyone! in this tutorial I will teach you all the things I learned about printing over the years! I will share with you general settings & practical tips for the most common use cases I experienced.
I'll divide the tutorial into two parts. From Canvas size & Preferences to color output & profiles while trying to give a more technical explanation of some of the key concepts to keep in mind.
I hope it helps!

Video tutorial

Please check the video tutorial for a narrated explanation▼

https://youtu.be/Rxx9KG7Tpgo

1. Canvas size

[1] Lets review the settings in [File] > [New]▼
■[1.1] Canvas size, width, height & resolution.
■[1.2] Measuring units. I divide them between physical (cm mm in) & digital (pixels) units.

▼ For digital, we select Pixels as our unit and simply define the canvas size. For example 1920x1080px
For web & screens, the resolution is usually set to 72dpi, but it isn't really important to the final outcome in digital. Focus on the final canvas size.

▼For printing, we need to pay attention to the relationship between the physical canvas size, the resolution & the final pixels.
For example, an A4 page is 29.7 x 21cm
■ At 300 dpi the final pixels are 3508 x 2480px.
■At 72 dpi the final pixels are 842 x 595 px.
Why does this happen?

1.1 Understanding Resolution

▼ Let's define a couple of concepts to understand how printing resolution works:
■DPI = Dots per inch. Its the amount of printed ink dots a printer can place in a 1-inch line (2.54cm)
■PPI: Pixels per inch. The number of pixels per inch displayed on a screen.
The two terms are often used interchangeably, even if they aren't technically the same.
For our purposes & to stay practical, we are going to call DPI the amount of "pixels" per inch printed or displayed.

So, for a given Physical size (in cm mm) the resolution defines the total amount of pixels in the image. At a higher resolution, there is a good amount of pixels or dots to cover the size of the page. So the pixels are small and we can't see them with the naked eye.
With a lower resolution, we still need to cover the same physical size with fewer pixels. so each individual pixel or dot needs to be Bigger.▼

Bigger "pixels" result in a percived loss of detail and what is called pixelation.▼

So, should we always just use 300 dpi?

1.2 Optimal resolution | Its not always 300dpi

While 300dpi is a number often recommended for print. It's not always necessary or even practical to use.
They are different factors that affect the decision of optimal resolution for print.
■ Printing methods & materials can affect the optimal resolution. For example, the printing of fabric is usually done at 180dpi, using more resolution can even cause the print to look less sharp in some cases. Some printing processes like using stochastic screens need even higher resolution than 300dpi.▼

▲ Sometimes it simply isn't practical to work at a high resolution.
For example, if we need to create a large format print of 2m.
■ At 300dpi would be an enormous size of 23622px. We would need a powerful computer to work with it. and even if our computer can handle the file it can cause troubles in other ways.▼

Even if our computer can handle the file, working with too many pixels can cause other problems.
For example, if I paint with the biggest brush size of 2000px on a canvas size of 3508px wide
I can cover a good amount of the canvas.
With the same brush and physical size, I go to [Edit] > [Change image resolution] and change the resolution to a bigger value. This results in a canvas 14032px wide. Now the same brush is a lot smaller & it also slows downs my pc. ▼

Try to achieve a balance between details & performance.
Next, I will cover probably the most important factor to choose the optimal resolution: Viewing distance.

1.3 Optimal resolution | Viewing distance

Prints are intended to be viewed at different distances depending on the size.
When choosing the optimal resolution we need to decide at what point we can no longer see the pixels in an image
We don't stand at the same distance when reading a book, looking at a poster, or a Billboard, if we stand further away from an image the pixels get smaller.
Here is a general guide assuming someone with good eyesight:
■Printed materials that viewers will hold are viewed at 30cm / 1ft. They need a minimum resolution of 300dpi
■ A small poster may be viewed at 1m / 3ft & needs a minimum resolution of 180dpi.
■ A large canvas print would be viewed at around 3m / 10ft & can be printed between 90 - 60dpi
■ A Billboard can be printed at 30dpi or even lower since its intended to be viewed from far away. lets say 10m / 30ft or more.

If we get close to a billboard we can easily see the printed dots. But when viewed at a normal distance the print looks good.
So basically the bigger the print the further away we are going to see it, so we can get away with lower resolutions.

1.4 Printing size practical guide

The easiest way to decide the optimal resolution is to work with physical units.
■Define the physical size first.
■Determine the viewing distance & resolution (dpi) using the reference chart. This would give us a good canvas size in pixels.
■While in doubt use a higher resolution that doesn't slow down your computer and is easy to work with.
■In pixels. A flexible canvas size that works for me is 7000px. It would look good even on 4k Screens & it would print well on multiple print sizes. Try to find a flexible size that works for you.

Using [Edit] > [Change image resolution] with the Fix pixel(C) enabled, pick a physical unit like Cm & change the resolution, it would keep the number of pixels fixed & change the physical size to an optimal size.
So we lower the resolution to print bigger & if we want a higher resolution we need to use a smaller print size.▼

1.5 Preview Print size

I think is a good idea to work around the optimal resolution for the physical size.
We can calibrate our monitor to preview the printing size on the screen.
Go to [File] > [Preferences] > [Canvas] > [Display resolution settings] This will pop up a ruler in the screen.
Grab a trusty ruler and align it with the screen. Use the slider if necessary to calibrate the monitor. Now we can preview the print size.▼

Here i have an small size physical size with a high resolution.▼

I can zoom in really close & work in some details.▼

Now lets go to [View] > [Print size]. The actual print size is pretty small, so all the little details I just painted are lost. We need to keep in mind the print size to avoid wasting time or making the image too busy.

Here are some bonus tips:
We can add a shortcut in the command bar to quickly preview the print size.
Rigth click the command bar and choose command bar settings.
Then select [print view] and click Add. An icon is added to the command bar. Press it to Preview the print size.▼

Another workflow tip is to create a new window and set it to print size. This way we can work in the main canvas and see how the details will look printed.
Go to [Window] > [Canvas] > [New window].

2. Color printing | Color models

I will give a brief explanation to understand how color works in clips studio paint.
Color models are a system of 3 or 4 primary colors that combine to produce a larger number of colors.
Two typical color models are RGB & CMYK

■RGB is an additive color model. The primary colors are Red Green Blue & are produced by light. Like the LEDs on a computer screen. The sum of the 3 at the maximum value creates white light.
This color model produces vibrant colors & is used on screens & digital files.

■CMYK is a subtractive color model. It uses Cyan Magenta & Yellow inks or paint to subtract color from reflected light, creating the different values. The sum results in a dark value.
To add detail in the shadows, Black (K) ink is added.
This model uses the white from the paper.
Typically used for printing.

2.1 Color space | profile

A color space is an specific implementation of a color model.
■For example two common Rgb color spaces are Srgb & adobe Rgb.
They define the way color is described & the amount of colors.
The range of colors is known as Gamut.
■Different profiles can reproduce a limited number of colors from the full color spectrum.
Adober rgb has a wider gamut than srgb so it can use more colors.▼

As a general rule, CMYK has a smaller gamut than RGB. That's the reason why when we convert colors from RGB to CMYK, the colors change, especially the brighter & saturated colors will not reproduce well.
We call this colors "out of gamut" since they are outside the range of colors the cmyk space can reproduce.

We can say that RGB & CMYK are relative color modes since they depend on the displaying device.
Two monitors would describe a particular color difference even if they are the same model.
Papers have different gamuts as well, so the same file printed with a specific printer would look different on each material.

To achieve consistent colors we need to embed the information. A value of "G :255" would look different on each specific device. so we need to "explain" how the original color is supposed to look.
To achieve this we embed the color profile in a .ICC file. The other devices will have the information they need to interpret the colors correctly.

This is a simple explanation of the concepts. To learn more read this articles ▼

https://tips.clip-studio.com/en-us/articles/909 https://tips.clip-studio.com/en-us/articles/909

https://tips.clip-studio.com/en-us/articles/553

2.2 Preview & select colors

To set & preview a color profile go to [View] > [Color profile] > [Preview Settings]
In this window select a color profile. Ask your print service what profile they need.
In this case, I selected a CMYK color profile.

We can use the Navigator window to compare the results of the color conversion to the original colors.▼

As you can see we lose the bright & saturated colors of the original RGB image. Since CMYK has a smaller gamut.

The rendering intent defines how the colors are converted
■ Perceptual: Compress the image inside the destination color gamut. it keeps the relationship between the colors so the original colors may change, but its perceived as natural. This intent works good for color correcting the image after the conversion.

■Saturation: Focus on creating a saturated image, it won't maintain the balance between the colors. It works well for cartoons & graphics but it can result in some artifacts.

■Relative colorimetric: Changes the out of gamut colors to the nearest value inside of gamut.
Some colors that look different on the original can get the same color value in the conversion.
This intent maintains the original colors inside of the gamut which is important for skin tones.

■Absolute colorimetric: Simulates the white of the paper. It only modifies the out of gamut colors.
This intent can be used for Proofing.

Choose the intent that works best for your image. The most used intents are Perceptual & Relative colorimetric.

Activate the tonal correction to color correct the image using a tonal curve or levels.
We can change the overall contrast or specific channels.▼

Same as we did with the print preview, We can add a shortcut on the command bar to quickly toggle the preview of color on/off. If our computer can handle it we can create a second window as well.

We can use the CMYK color slider to select colors inside the CMYK color gamut.▼

If we select a color outside of gamut & change a value on the sliders it would change to the closest value inside of gamut.▼
■Keep in mind that Blending modes & correction layers can still result in out of gamut colors.

2.3 Export the correct colors

To export the file for print go to [File] > [Export single layer] and choose a file type without compression like .tif or .psd▼

■In the export window select the correct color space. The color profile set for preview its the one used. If we didn't set a color profile the program will use the default one from [Preferences] > [Color conversion]
■Make sure Embed icc profile is selected.
■If you need you can change the output size.
■Remeber to save a copy of the original file. CSP works in Rgb. it can preview & export cmyk but if we open the exported file it will be converted to rgb. This can cause color degradation.

Hopefully after exporting you will have a beautiful file ready for print.

2.4 Practical guide to choose colors.

■Whenever possible work in a calibrated monitor with a wide gamut.
■ Ask your printing service what color profile they need
■Setup the color profile for preview & check out of gamut colors.
■If using CMYK know that while it will look good on print, we have limited colors.
■Use the CMYK sliders to pick colors inside of the gamut.
■Export a file type without compression (.tif .PSD)
■Select the proper color space & embed the profile.

■RGB give us more flexibility.
■Wider gamut alow us to create vibrant colors.
■ It looks great on screens.
■ A lot of modern digital printers prefer RGB files & make the conversion themselves.
■ Some printers even add more inks to achieve a wider gamut than CMYK like the extended gamut CMYK-OGV That adds orange green a violet inks.
This printers can reproduce more colors, so we are limiting ourselves by working in cmyk.
■I prefer to work in RGB keeping in mind that some saturated colors may not look the same on print.

No matter what settings you choose a lot of factors can change the printed result.
Its always important to make a test print to check colors before printing a full batch.

Closing thoughts

Color printing can be a complicated subject to understand, so keep in mind some of the technical aspects and approach it in a practical way.
Remember to ask the printers for technical advice if needed.

I hope you can apply some of my information to your own workflow.
Be creative I have fun experimenting.
Thank you for reading.

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