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Resolution and Bit Depth

Lesson 17 from: Photoshop for Beginners: Essential Training

Mark Wallace

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Lesson Info

17. Resolution and Bit Depth

Mark explains image resolution and bit depth. You’ll need to understand these concepts for the best color and image reproduction when printing or exporting a final image for the screen.

Lessons

Class Trailer
1

Class Introduction

00:52
2

Introducing Photoshop

02:37
3

The Class Materials

01:36
4

How To Open Files

01:42
5

Using The Home Screen

02:35
6

Exploring The Interface

03:30
7

Getting Additional Help

01:36
8

Understanding Workspaces

05:11

Lesson Info

Resolution and Bit Depth

let's talk a little bit about image resolution and bit depth. Now this is something that you might need to know when you're printing documents or using filters and some other things in Photoshop. So I'm gonna give you a very high level understanding of what this is. You don't have to know a lot about it. You just have to know a little bit about some of the concepts. So we're gonna look at an image here. This is cami in the rain and this is a shot that I took with my Canon R five. So it's a pretty high resolution image. So what does that mean? Well the first thing we can do here is we can go up to the image and then we can go to image size and we can get a little uh idea of all the different things that this image has in it. So we can see that. It's 100 and 28 megabytes. That's the file size on a hard drive. It doesn't really matter too much except for hard drive space. The other thing we have here are the dimensions is how many pixels make up this image. What the heck are pixels? Well ...

let me just go and show you what a pixel is. So if we zoom in all the way. So as much as we possibly can you'll see that this image is made up of little tiny dots. So every digital image is made up of little tiny dots. Those tiny dots are called pixels. And so as we zoom out, those pixels look a little bit more and more like something. And so that's what we have. We have pixels. And generally speaking the more pixels, the higher resolution because we can make better transitions between different areas of the image. So we want lots of pixels. And so it's not just about how many pixels are in an image that make up the resolution of the image resolution as the name implies is how do those pixels resolve themselves? And so once we go back here again to image image size, you'll see something here. So we know how many pixels that we have in this image. And so we've got thousands of pixels wide, thousands of pixels high. But what we want to know is this resolution, how many pixels per inch or how many pixels per centimeter or how many pixels for? Per inch on a screen or dots per inch sometimes it's referred to. And so what that means is when you print an image and you have let's say one pixel per inch. Well that image is gonna just have one block. It's not gonna look like much. If you have two pixels per inch you have two blocks. The more pixels per inch, the more detail you can have in an image. And so you want more pixels per inch. Traditionally something of 242, pixels per inch is print quality. And for a screen. Normally you would have maybe 72 or 96 pixels per inch on a screen. But that's really determined by your monitor and how it does all of its pixels. And so really we're concerned with how many pixels do we have per inch? That's the resolution. And so we want higher pixels per inch for better prints and better display. That's sort of the the understanding there. Okay so let's go and look at bit depth and how all of that works. So we've got all these pixels and we have a bunch of pixels per inch. But what can we do with those pixels? Well when we zoom in again we're gonna zoom in way in. So we're gonna zoom in appear on you know, all these different areas of blue. So the background notice that there are dark blue and light blue and there's all kinds of different blues here and they transition into this sort of lighter gray. And so the bit depth is, how many levels of color do we have per pixel. How much color information is available per pixel. And so to illustrate this, let's go and look up here at image and then we have mode we have eight bits per channel 16 Serving in 16 minutes Per channel and 32 bits per channel. And we have index color and grayscale. So the more bits you have per channel, the more color information. Let's go all the way down to a grayscale image. And we're gonna discard some color information. And then we're gonna go all the way down to bit map and we're gonna flatten layers. Yes. Okay so what this does this is a bit depth of just one basically. So we have black or white. That's it. We don't have any color information and we go all the way in. So we'll go up here Camille's face, we're going to go all the way all the way all the way in. You can see that we either have black or white, nothing else, no shades of gray, nothing in between. So this is the lowest bit depth possible if we go up one. So let me go up one here to grayscale. So I used my undo my history palette to do that. Now we see that we don't just have black and white, we have shades of gray. So the more bit depth the more information you have per pixel. And if I zoom out you can see that this grayscale looks a lot better. Now. If I undo that we're gonna go back here let's make this image I guess it's eight bits per channel. Okay so that's what was shot and we go all the way in let's go all the way in back here and we can see that we have all these different variations of color in each of these pixels. So we're not just at black and white were at different colors and in different shades of each of those colors and the different luminosity levels. And so the bottom line is when you're looking at the image resolution and bit depth you want the largest file size. The most pixels that you can get. That is determined by your camera that you're using or the scanner that you're using and then you want the most pixels per inch. Again, generally that's determined by the equipment that you're using to capture your image and the highest bit depth. So you have the most color. Again that's usually determined by the equipment that you're using capturing those images. If you're creating something in Photoshop from scratch and you're illustrating and painting you would like to make it a high bit depth and a high lots of pixels so you can print. And so that's sort of image resolution, image size and bit depth at a very high level. Now there is one gotcha. And that is that for some of the filters that we have, they do not work in an image That is 16 or 32 bits. So so for some of the filters that we're gonna be showing you later on, you'll have to make sure that your image is at eight bits so that those filters will work and you'll know that because you'll get a warning dialog. And so sometimes those are filters that you either you don't use or you use at the very very end of your editing so that you keep as much color as possible all the way to the very end. So that's all you have to know for image size and bit depth.

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Ratings and Reviews

Katie
 

Mark did a great job at explaining things and going over them multiple times throughout the lessons. My only issue was that sometimes it went a little faster than I could keep up and I needed to rewind it a bit and start again. But from someone who has never worked in photoshop before I 100% recommend this class to anyone trying to learn.

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