LESSON 4.1
INTRODUCTION TO PHOTOSHOP
DURATION 1 LESSON
Key concepts: main tool bar, fly-out menus, main and sub menus, palettes, the workspace and layers.
Key tools: selection marquee, constrain modifier [shift], gradient fill
Major concepts: Tool sub-menus, saving authoring files (.psd) and exporting output files (.jpg)
In this lesson we will be introduced to resolution, DPI, and the graphical user interface (GUI). This layout will look very familiar, as it resembles the organizational layout we just learned in Adobe Illustrator. We will look at the location of tools and navigate the basic interface, pointing out important concepts and tools along the way.
Once we have been familiarized with a few tools, you will create a 3D sphere using some basic tools and post the output file on your portfolio.
LESSON 4.1a
INTRODUCING THE INTERFACE
Watch on YouTube
Understanding Image Resolution
Terms: pixels, dots, PPI (pixels per inch), DPI (dots per inch), raster, vector, screen resolution
In this class, we are mainly concerned with digital images, but we must also understand how what we see on screen turns into an image on paper when we send it to the printer. To understand this, we must understand resolution.
Resolution is the amount of detail in an image.
There are two ways computers can show an image. Raster, and vector. For this lesson, we will be concerned with raster images. To understand raster images, you need to know what a pixel is.
Think of the screen in front of you as a detailed sheet of graph paper. Each of the boxes that make up the grid in your graph paper can show only one colour. These tiny boxes are called pixels.
If your entire screen was black and you got close enough, you would see each of the tiny boxes (or pixels) and since they can only show one colour, each of them would be black.
If the screen was all white it would be the opposite, and if you got close enough you would see tiny boxes, or pixels, filled with only white.
Below this line of text, you can see a single grey line
If you were to get close enough, you would see a single line of grey boxes, lined up like this:
Drawing curves
Now, this isn’t only true for straight grey lines. Every image you see on a screen is shown to you by assigning pixels a specific colour value, sometimes white, grey or black, but often any of millions of available colours. Each pixel is the same size and when viewed as a whole, shows you an image.
Since what we see on screen isn’t always straight lines like the grey line in the example above, the computer tries to smooth out curved edges by shading some boxes between two different coloured items, so that when we view the shapes at normal size, things look smooth. Here is a green circle on a black background. Next to it, you can see the pixels used to make the green circle appear smooth.
We referred to the screen as a kind of sheet of digital graph paper. Each of the pixels making up the grid is assigned a colour value, and when viewed at a small enough size, combine to display an image. Sticking with the idea of a sheet of graph paper, imagine you were working with a sheet of graph paper that only had 10 boxes across the top of the page, and 15 boxes along the side. Imagine drawing a circle, like the one in the picture above. You would only have 150 boxes to make your image. The circle would probably not be very smooth, since you don’t have enough boxes to smooth out all the edges.
Now imagine if instead, you had 1000 boxes across the top of your grid and 1500 along the side. That’s 1.5 million boxes! But to fit that many boxes onto the page, each box would have to be much smaller. This, essentially, is what happens with high resolution images. By fitting in more pixels, into the same amount of space, we are able to add higher detail, and thus, higher quality to an image. Here is the same green circle, and a close up of the pixels used to make it. Notice how much smoother the higher resolution version is. Notice also, how much smaller each pixel is.
DPI: A measurement of image detail
DPI stands for dots per inch (sometimes, resolution is referred to as PPI, or pixels per inch, but these mean the same thing). Since images can be any size we wish, knowing the number of pixels across the entire image does not give us enough information. We need common denominator so we can compare values. We use DPI to understand how many dots, or pixels fit into an inch of an image.
If you are working with an image that is 100 DPI, that means there are both 100 horizontal dots and 100 vertical dots, which gives you a 100 x 100 grid in a single square inch. That means you have a total of 10,000 individual dots (100 x 100 = 10,000).
Important resolutions
72 dpi. When we open up a new image in Photoshop, often the resolution will be set at 72 dpi. This is based on what is known as screen resolution. This number is based the display limitations of older monitors, but isn’t really relevant now because screens have become so much more advanced.
300 dpi. On a screen, the dots we refer to are pixels, but if we are printing something the dots we are referring to are tiny dots of ink. The smaller the dots of ink, the higher the resolution. The higher the resolution, the higher the quality and thus, the clearer the image. The human eye can’t see any difference between 300dpi and anything higher quality than that, so we use 300dpi for any printed materials (the exception being newspapers, which print at lower quality to save ink and cut costs).
So why not use 300 dpi all the time? Think back to our green circle. If we wanted to print an image at 8″ x 10″ at 300 dpi, the file would need to have the following dimensions:
8 inches x 300 dots per inch = 2400 horizontal dots
10 inches x 300 dots per inch = 3000 vertical dots
That’s a total of 7.2M pixels! Each of those has to have a colour associated with it (green, black, white, or any of the millions of colours) and that affects file size. The more information (or the higher the quality) the higher the file size. The implications of this are different for web and print based applications, and will be covered in a later lesson.
LESSON 4.1b
3D SPHERE GRAPHIC
In-class activity 4.1
Using the elliptical marquee tool, the gradient tool and the brush tool, create a 3D sphere. Add a shadow on a separate layer behind the sphere.
3D sphere tutorial :
Create a 3D sphere using selection tools and a soft-edged brush
Watch on YouTube
Extension activity: Bowling ball
Using the skills you just learned, make a bowling ball.
REVIEW QUESTIONS
Blog Entry 4.1: Intro to Photoshop
Create a blog post (titled 'Intro to Photoshop') on your WIX website that includes your sphere and your bowling ball. Categorize your blog using the Photoshop category.
Include the questions and answers below in your blog entry
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In the video, I discuss this idea of graph paper to explain what is happening on your screen (in terms of resolution). Explain this concept in your own words.
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What does DPI stand for? Explain why this measurement is needed for images.
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Identify 3 similarities between Photoshop and Illustrator
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Identify the 3 differences that you think are most important between Photoshop and Illustrator (so far)
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Why is it important to note that the History palette gets cleared when you close a file?
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I mentioned 'marching ants'. What was I talking about?
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What does the grey and white checkerboard indicate in Photoshop?
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Write a short paragraph about your experience with this activity.