Changing Canvas Size
Let's take a look at another command which is slightly different but also useful to know about, which is called Canvas Size. So Image Size is used for when you say, how big is my file in terms of dimensions, all the stuff we talked about, and I wanna be able to scale it up or down. Canvas Size, you need to think of it almost like we went into the craft store and bought a physical canvas on which we were going to paint. If I had done that, and this obviously wouldn't work in the real world but let's just pretend, so I went and bought this canvas. And it was three feet wide and I was painting. I thought, oh I wanna paint some more over here, but I've run out of canvas but I need more, so I'd have to go to the store and buy another canvas and somehow stitch them together. That's what Canvas Size is in Photoshop, where you need to add more room to the image. So it's not going to scale this existing pixel in for me. It's gonna add more to it. So if I scaled down a bit, you can see there's t...
hat same photograph, and let's say I wanted to add, try and add some more of this photograph by artificially copying it or something. I need somewhere to put it, 'cause right now, if I go to this command, remember Image Size said it was 900 pixels. Canvas Size also says it's 900 pixels. So if I just clicked OK, there'd be really no point in using this. What this allows me to do is say, but I want more pixels to add more information. So I'm basically adding artificially more room on to the edge of this to do something to it. So down at the bottom, you'll see there's this thing that says Anchor, and this determines where do you want this extra canvas added? By default, it assumes around all four edges. That's just what it defaults to, which is neither here nor there. I want to add more canvas to the right side in my scenario, so that means I want to anchor the left side. So see how the arrows kinda change, they only add canvas this way. So now whatever number I put in, it will say: I'll keep the left-hand edge as it is and I'll add more canvas on this end. So, let's say I want 300 more pixels, so I do the math myself and say 1200 pixels. Notice how the height doesn't change, 'cause on like Image Size, these are not linked to each other. These are independent, and when I click OK, it basically says: Okay there you go! Now, you got more canvas. Notice how it didn't automatically say, I'll just fill in more photo, 'cause there isn't any. But if I wanted to artificially do the kind of things we can do in Photoshop or maybe add another photograph and blend them in, I need somewhere to put it. So that's what Canvas Size does, is gives you a bigger overall canvas that you can work with. We don't necessarily have to use this all the time, 'cause if you had a big photo and you wanna put a small photo right in the middle of it, there's no reason for extra canvas. If we were trying to create, say, a layout of several photographs and you start and then realize, I didn't make my original photo quite wide enough, that's where Canvas Size can let you give yourself more room. It doesn't add pixel information. In this case, you'll see it's got this checkerboard thing, which as we'll see just means nothing. It's just transparency. But now, at least, I could do something like bring another photograph in or do whatever I wanted. Maybe I just wanna add a white box with type on it or something, but I needed somewhere to put it. So that's the important difference between the two. Image Size actually scales the physical image up or down. Canvas Size is saying, I'm gonna give you more room to work. So, it's one of those things where some people say, I'm still not sure. When should I used Canvas Size versus Image Size? And you probably already know the answer is: Well, it depends. What are you trying to do? If you're trying to add more information that wasn't there before, you need more canvas to put that on. Some people like to think of Photoshop always in the context of painting, 'cause it kind of helps them figure things out. And this is not a bad example of that, whereas if you bought a canvas that was this wide, that's the extent of it. But if you wanted to add more painting on here, you'd have to have more room to do it, so you'd need a bigger canvas. So that's what Canvas in Photoshop's terminology means. It's still gonna add to the file size, 'cause ultimately we'll be adding more pixels, but we're not massaging the existing pixels. We're adding more room to put more pixel information on there. So as you saw in this case, the original photograph of the ice didn't change. I just have more space on the side to do something with. And because of this, now if I go back to Image Size, you'll see they do work hand in hand. Now the Image Size is bigger, and it's saying 1200 whereas before it said 900. But again, the photograph itself wasn't affected. It was just the canvas on which the photograph was placed, so to speak. It's not, I mean, I think it's good to think of it that way from a painting standpoint, but when you open a photograph, you're just opening a photograph. But from a Photoshop terminology standpoint, it's as if that photograph is sitting on top of a canvas. And if you choose to do certain things, you need to make the canvas bigger. So, for example, if I decided this photograph would look great if it was rotated on a angle, if I go to rotate it, it's gonna get cut off at the top or the bottom, 'cause the canvas isn't tall enough. So I'd have to make the canvas taller to have room to put something on an angle. So, more often than not, the purpose for increasing the canvas is 'cause you need to do that to accommodate whatever you're trying to do. You know, add some more information, add another photograph, whatever it might be.
[Male Audience Member] So if you selected on the cropping option that you didn't want to discard the pixels,
where is that information, is my first question or the first part. Second part is if you didn't delete those pixels, when you do something globally to the rest of the image, are those affected?
And then, last but not least, relative to the Canvas Size and your Image Size, is that information still attached?
Okay, good bunch of questions. So, the cropping part, if you do a nondestructive crop, it's kind of in your file. So what's gonna happen is, visually, it'll look smaller, but in terms of file size, it's still gonna be, in affect, the same size so you haven't really got rid of anything. It's still there. If you're making global changes, it depends how you do those. Other words, when we talk later on about adjustment layers, adjustment layers affect every pixel below. So even the ones that technically aren't visible, soon as you make them visible, they'll be affected, because now they are visible. Whereas if you did some other method of adjusting, you'd probably say, oh it doesn't look right, because the original crop is affected, but the other pixels aren't, so it kind of affects that. And then, the Image Size, Canvas Size part, it's almost, that's gonna be more based on whatever you're working with the moment. So when you're doing any kind of math, you have to, sort of, discard the fact that you've done that temporary crop thing, because it's gonna kind of mess up your math a little bit.
If you are, say, doing a page in a book, and you're gonna do nine images, 3x3, do you need to take into consideration the canvas size at that stage? Or is that a later feature when you're laying out and arranging them for us?
I would say, I mean, if you're gonna ultimately take those photos you've worked on separately and combine them all into one, then it's at that last stage I would think that that's the page as your final destination. So as long as that is the correct dimension resolution, where you'd have to consider it is, to make sure that, in that case the resolutions are the same. Meaning, if you've determined that it's, say, a 10x10 page at 300 and this one's 2x3, it should be a 300 as well, 'cause then the 2x3 inches will stay the same when you drag it into the 10. Otherwise, if the res' one's off, it could scale slightly up or down, and your math would be a little off. So, one of the factors, when I had said before I don't really talk about resolution, except for printing. So if I know the final result is printing, that's a factor all along the way. Any decision I make, I wanna make sure that whatever resolution I'm aiming for stays constant. Otherwise, you're gonna see some slight sizing differences.