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In this movie, I'll introduce you to a couple of very important topics that are critical to your understanding of Photoshop, specifically in the larger realm of digital imaging in general. Now, I'm looking at this kind of psychedelic weave. And this far out, it looks to be extremely smooth, with these dark and light lines fading in and out vertically. And the colors fading back and forth horizontally. But like any digital image, this one is made up of pixels, and if you ever want to see those pixels, all you have to do is zoom in.
I'm going to press and hold the Z key and drag to the right in order to zoom. And even before I get to the pixel grid, it's obvious this image contains pixels. Once I go beyond 500% and I can see the pixel grid it becomes more obvious still. Now by the way, if at any time you want to hide the pixel grid, all you have to do is go up to the View > Show > Pixel Grid, to turn the command off. And sure enough, we've got a bunch of pixels.
In fact, this close in the image looks comically simple, almost like something out of the game Minecraft. The number of pixels that work inside of an image is known as the image size. So I'm going to go ahead and switch over to this graphic image right here. Which contains a couple of drawings I did with my kids a few years back. And these graphics are going to help us understand some key topics up front. We'll see how image size and resolution affects photographic images later in this cahpter. Now notice I'm viewing the image at the 100% view size which means that it's a very tiny image indeed. Often times you'll hear folks call this short of image, low resolution or low res for short.
But really, the more accurate way to describe it is small because it just doesn't contain many pixels. Now, I'm going to tour you through this image using what's known as Layer Comps. And I'll explain what's going on with Layer Comps in a future course. But, for now, if you want to see them, you can go to the Window > Layer Comps, to bring up the Layer Comps panel. And I'm just going to be advancing through each of these guys. The Layer Comp, in its most simple form, saves which layers are turned on and off.
Now I'm not going to need the panel, because I've set up a custom keyboard shortcut that allows me to advance from one comp to the next. Now this image, happens to measure 918 pixels wide by 632 pixels tall. Which means that we've got a total of 918 times 632, which equals more than 580,000 pixels. Now, at first glance, that might seem like a lot. And it would be if we were talking about dollars, for example.
But in the world of digital photography, that's nothing. Consider that a low end digital camera starts off at 12 megapixels and the high ends are somewhere in the 20's. Which means that we're talking about 12 to 20 million pixels, inside a photograph. Now the definition of image size, by the way, is that it describes the pixel dimensions and the total pixel count. In this case, what we were just discussing, 918 by 632 Equals 580,000 pixels.
Every single image you ever open or work with inside Photoshop has an image size associated with it. Meanwhile, there's Resolution, which is really like pixel population density. It's the number of pixels packed into a linear inch or millimeter. So in this case, for example, the resolution of the image, and I'll show you how to set that in a future movie, the resolution is set to 100 pixels per inch, also known as 100 ppi.
Which means that we have 100 per horizontal inch by 100 pixels per vertical inch, and therefore we have 100 times 100 which is 10,000 pixels in a square inch. That mean seem very high, but actually it's a very low resolution. And, something to know about resolution, it applies to print only It is meaningless for screen graphics, so if you're talking about a web graphic for example, you don't need to worry about resolution. Now you might say well Deke back in the previous chapter you were talking about screen resolution when you were discussion retina display, and high DPI monitors. And that is true.
So I'll go ahead and switch over to this graphic here, and just because it contains a Photoshop interface of its own, I'm going to press Shift + F in order to hide Photoshop's real interact here. So here's the retina display image. And the screen has a resolution of 2880 by 1800. That is a total of more than 5 million pixels, and it works out to a resolution of 221 pixels per inch. That's the screen's resolution.
It has nothing to do with the image resolution. The resolution of this image, happens to have been set to 300 pixels per inch. And that is entirely independent of the screen. Now, imagine if we had a hypothetical screen whose resolution was, essentially, half what we just saw, 1440 by 900, which is one of the possible settings with the monitor I'm using here. Which would be a total of about 1.3 million pixels or a 111 pixels per inch. In that case, the photograph would look like this instead. Still shown at the 100% view size by the way, so both of these images are appearing in at a 100%.
It's just because the screen display fewer pixels. Those pixels are going to be much larger and we're going to see less of the image at a time. So, the moral of the story is, image size is applicable to every single image you create because it describes the physical pixel count inside the image, whereas, resolution is only applicable to images that you intend to print. And those are the basics of image size and resolution throughout the world of digital imaging, as well as right here at home inside Photoshop.
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