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Because pixel-based images are made out of little mosaic tiles, there's a limit to how much you can scale them up without causing degradation of detail. The time-honored rule of thumb for print images is 300 pixels per inch at final size. Now if you're in control of the photography, you can ensure that the appropriate images are available. But you don't always have that luxury, do you? Your own clients may provide less than optimal images, and you have to make do. So what can you do? Let's take a look at this image. If I go to Image and Image Size, it's very small, just a little over 2 inches by a little under 2 inches. And what if I need this at about four times the size? Can Photoshop help me out? Well, let's see.
If I go to Percent and choose 400, it's going to make it a lot bigger. Oh! Look it's going to be 300 Pixels/Inch, so it should be okay, right? Not so much! When you zoom in, you can see that it wasn't a very good image to begin with. Photoshop has tried to interpolate pixels, it's trying to make stuff up where there wasn't anything there, and it looks very soft and very out of focus. And the truth is there's really nothing you can do about this. Photoshop tries real hard, but it can't make stuff up that isn't there. What can you do? You can just sort of accept the results, just know going in that it's going to try, but it's not going to be the best image possible.
Of course, if you can get a new image that's the correct size, do so. You just rarely have that opportunity. When you're creating your own work, maybe you're combining images, you may find that you want to scale and rotate and skew and experiment, and you are not really sure how this is going to end up. Now that you have seen the penalty for scaling up, scaling down, and so forth, maybe that makes you a little hesitant. Let me show you an approach that may give you a little more flexibility. Now I have a couple of layers over here because I'm experimenting, and what happens if I want to scale this girl down and she's just sort of dominating the image? So I am going to make her a little bit smaller.
So I am going to select her layer, go to Edit > Transform > Scale, and I am going to do this numerically. So up in my Options Bar, I am going to set the Width to 50% and link that to the Height. Well, she looks okay, and now I'm going to commit, but when we compare it to the original, well, of course she is smaller, we have to suspect that we've lost some detail. What happens if I restore her to her original size? So I am going to use my keyboard shortcut, Command+T or Ctrl+T, I am going to go back up here and set this to 200% which is going to restore her to her original size, commit to that, Transform, and then when I move her around and zoom in, you can see that we've lost detail, look at the eyes and look at the teeth and that checked pattern on the scarf around her neck.
Photoshop has done a pretty good job, but clearly we've lost some information. So that means that if I keep experimenting, I am going to lose even more information. So what can I do if I know I want to keep changing her? What I can do is I can turn her into a smart object. All I have to do is select the layer, go to the Layers panel menu and choose Convert to Smart Object. You can see there is a little decoration on the corner here, so what does that mean? That means that it's actually storing the original information in the Photoshop file. It's not linked to the original image that I placed in here, it's locally stored, it's inside this Photoshop file, and it gives me this kind of flexibility. I can scale her way down.
Let's see, I am going to scale her to 25% in both directions or she's going to look really skinny and then commit, move her around. Now what happens if I scale her back up? So I am going to use my keyboard shortcut again. This is kind of interesting. Notice that it recognizes that that content has been scaled down to 25%. It didn't do it with the plain old image, but it understands that with a Smart Object. So all I have to do to get her back to her original size is scale her to 100%, move her back up, let's zoom in, and we haven't lost a thing.
So one of the advantages of Smart Objects is that you can scale, rotate, skew, whatever kind of transform you want to perform, and you can always get back to the original. Now, don't let this mislead you. This doesn't mean that you can take a little bitty image and scale it up as a Smart Object and get better results than we did a minute ago in that other image. It can get back to the original, but you still have the same rules when you try to go beyond the original size. Now, it adds a little bit to the file size, but it gives you such wonderful flexibility. When you place Vector art in, it automatically becomes a Smart Object.
Again, look at the lower right hand corner of my little thumbnail. You can see that little decoration that indicates that this is a Smart Object. So I am going to scale my little bear way down, it's going to get really, really tiny. But remember he's vector, so there aren't any pixels to throw away. And when I scale him up, I can scale beyond his original size and Photoshop is going to look at that original vector information, and it's going to scale that vector information up. So Vector objects as Smart Objects, there's no limitation to what you can do to them.
Just be a little cautious with raster smart objects, but remember that great flexibility that they give you. Now if you have to build software manuals, and you have screenshots, when you take a screenshot, it's the resolution of your monitor. So if I go to Image > Image Size, you can see that it's 72 Pixels/Inch. Now after I just told you that everything should be 300 Pixels/Inch, if you can. Well, that looks pretty awful. So, if you're tempted to scale this up, watch what happens. If I go to Image > Image Size, and I set this to 300--I am going to Cancel on this one because I already have an image to show you--what's the result? Look how nice and sharp this is. Look how nice and blurry that is.
So here's my original screenshot. If I scale it up to 300, or I change the Resolution to 300, it doesn't improve it, does it? So what can we do? 72 sounds so scary. The truth is that I could use this image at its original resolution in print and if I put it in at 100% and it's going to look just fine. But that makes some people twitch when they see that 72. So let me give you a little advice. If you're going to scale this up and if you are going to give it a higher resolution, do it this way, go to Image > Image Size, set that Resolution to an even multiple of the original.
So here I have started with 72, and if I had done the screenshot on a PC, it would probably be 96. So I am going to set it to 288, four times the 72, and I am going to choose a special method, Nearest Neighbor. Notice that it says preserve hard edges. Remember Nearest Neighbor when you have screenshots because that's the way to go. When I click OK, look, it's nice and sharp, it has a nicer resolution. What I do sometimes if I want to make sure that my editor isn't going to freak out, I'll go back to Image Size-- sometimes people freak out when they just see the 288-- I uncheck Resample Image, I change that Resolution to 300.
What that means is that it's not making new pixels, it's just making the existing pixels a little bit smaller. When I click OK, nice and sharp, and I haven't lost anything. That's your overall goal, you don't want to lose any information, you want to maintain detail, and you have to understand the consequences if you're forced into a position where you have to scale a little bitty image up, just have a realistic notion of what the results are going to be.
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