Resolution next to pixel dimension
I can confidently say that most designers have only a superficial understanding of resolution, often equating it with a 300ppi file. They might create such a file or simply change the resolution of an existing one through the Image Size window. However, the concept of quality in printing and its relationship to resolution is not limited to this number. Key points in this topic can guide you to a better outcome, almost like a miracle.
After reading several previous articles, like Bit depth or File resolution you must have realized that much of the information in the public eye is based on basic settings and some predetermined values. But this is not the case for us, as professionals or prepress managers. In fact, these are the theoretical and scientific foundations in our documentation, and someone who makes a conscious choice based on a complete understanding of this subject will undoubtedly achieve more different and impressive results in the printing industry. That's why I want to talk a bit about resolution in a file before we go to the printing press and lithography.
To put it simply, when you work with a raster-based software like Photoshop, that program has no understanding of metric dimensions! The only thing it understands is pixels. When you check a file in Image Size, you'll see an indicator: Pixel Dimension.
What are these two numbers?
Let's take an example and examine the values in the Pixel Dimension section: Take a picture with your mobile phone. Let's assume your camera quality is 50 megapixels. Now open the image in Photoshop and go to Image Size. Multiply both numbers in the Pixel Dimension and see what you get. Approximately, you will reach the same number of 50 million, and this figure is the same as the pixel area in your image. Now let's examine the subject a little more closely and create a connection to the concept of resolution.
Resolution enters the scene!
This is where we need to look at the subject from a different angle: "When we need to examine the file based on metric dimensions." For example, preparing a file for printing in specific dimensions. Here we need to tell Photoshop how to set the units of measurement. When we want to define resolution, we usually have two units of measurement available:
Pixel/Inch (PPI) and Pixel/Centimeter (PPC)
Most printing houses work with PPI units and measure the meaning of quality and resolution with this unit. But you can also ask the production manager to be sure. This is where a specialist is identified, because they are not supposed to act like a robot based on some predetermined information, but by understanding the file and the path it is going to take, they analyze the design and printing cycle to make the best choice.
I promise to make this completely clear to you with an example: Imagine opening a file with a resolution of 72 PPI. Activate the rulers, change the unit of measurement to inches; now place a guideline at the edge of one inch. Now if you count the number of pixels in this range, you will see that it is exactly 72 units.
In this way, wherever we give Photoshop metric dimensions, 72 pixels per inch are created in Photoshop's analytical system, and it calculates all sizes based on this. Even in other units like Cm or mm. For example, you need a 2×1.5 rectangle; according to the previous points, these numbers must be calculated and produced to create pixels: (2×72=144px) , (1.5×72=108px).
A very important point
You have certainly downloaded an image many times and in order to convert it to a file suitable for printing, you have changed the resolution from any arbitrary number to 300 with all your might. Of course, this number is usually 72 when downloading, but the point is not just in changing the resolution. Because understanding the concepts and paying attention to dimensions and the number of pixels prevents any arbitrary activity.
I think it's better to wait a bit because I want to ask a key question. In the following example, there is a 6-megapixel image with an area of 2835px × 2314px = 6560190 and an initial resolution of 72PPI.
Okay. Now I want to change my file to 300ppi resolution. Let's check the Pixel Dimension and area and even the number of pixels again in the new state: 11812 px × 9641px = 113879492.
Observe the difference between the two images with two different resolutions. Be sure to pay attention to the number of pixels in the first and second files, which is about one hundred thousand pixels:
113879492–6560190=107319302
Several questions arise here for you: First, is this amount of pixels added to the image?! Second, on what basis is their color information organized? Third, does increasing the number of pixels arbitrarily increase the quality of the file? Fourth, if I increase the resolution by a small number with any resolution, will it create a satisfactory result for printing?
Tips for the future...
This is the biggest disaster when resizing and modifying file resolution. Because the number of new pixels created by changing the resolution only exists in the file. But this creation process does not increase the quality of the file. Although increasing the resolution means more pixels per inch, the color information of each pixel is something that should be considered because there is no such thing as artificial intelligence here.
Although a larger number of pixels can mean better quality, it is when the initial number of pixels is high. If you suddenly change the resolution from a low unit to a very high unit, you have only increased the number of pixels and the final area, but the quality has been lost and this can be problematic in preflight principles.. Carefully review this article and valuable tips will be provided for you in the next section.
