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In this exercise, I'm going to introduce you to the somewhat confusing notion of image resolution. I'll show you how Illustrator makes it even more confusing. I'll show you how Photoshop handles image resolution beautifully. So the moral of the story is get the resolution right inside of Photoshop before you import the image into Illustrator. All right, so at the end of the last exercise, I went ahead and saved over the original Sepia image.psd file inside the 20 images folder. So I did the exact same work I did before and then I saved over the original image, which is important because that image had already been linked to the Final advertisement.ai file that we have seen a few times over the course of this chapter.
And so since I have made a modification, Illustrator is going to be savvy to that modification. But I went ahead and saved this image at a different resolution. I'm just telling you that upfront. How do you know what the resolution of this image is? Well, you go up to the Image menu, and you choose the Image Size command. Now this is such a useful command here inside Photoshop, that's where I am, that you can press Ctrl+Alt+I or Command+Option+I in order to bring up the Image Size dialog box. And notice that the Resolution is set to 220 pixels/inch. Now what in the world does that mean? That means that there are 220 pixels packed in every linear inch of this image.
So 220 pixels per the width of an inch, and 220 pixels per the height of the inch. So that means in a square inch you have 220 times 220 pixels, which is 48,400 pixels which you would really think would be enough pixels to get the job done. But it actually falls short of the commercial print standard, which is 267-300 pixels per inch, and we'll come back to that in just a moment. But anyway, 220 is what it's set to. Go ahead and cancel out for now. And what that does is that determines the physical print size of the image. It also determines how big the image is when it imports into a print application like Illustrator or InDesign or what have you, all of which are resolution savvy.
All right, so I'm going to go ahead and switch over to Illustrator. I have open right now the Final advertisement.ai file and so notice when I switch over to Illustrator by press Alt+Tab or Command+ Tab on the Mac, it recognizes that the file has been changed. It says hey something has happened to one of the linked files. Do you want me to update it or not? And you would say yeah, absolutely update it. So we have the most recent version of that image. All right, it doesn't look any different than it looked before. And if you have been following along with me, as long as you did all the steps right, it should look the same as well. But something has happened because I was telling you there is a different resolution value at work right now. So go ahead and press Shift+Tab to bring up the Layers palette or at least I'll because my Layers palette is currently hidden. And I going to twirl open the image layer.
I'll find Sepia image.psd. That was the image we were just playing with a moment ago. Meatball it to select it. Sure enough, that's the image right there. If I go up to my Control palette, I can see that it is a linked file and I could click on that little link there to bring up the Links palette if I wanted to. I can also see, hey, there it is. Sepia image.psd. And I could hover over that option to see the exact path for the image on disk. And then I go over here Transparent CMYK. So far so good because I did convert it to a CMYK image and it does have transparency and it is not 267 pixels per inch. What in the world is that about? So PPI, pixels per inch, 267. No, it's 220. I just saw it a moment ago.
Well, let's confirm things. You can bring up the Links palette either by going to the Window menu and choosing the Links command or just by going to this link right there. So let's click on that guy and then click on the fly-out menu icon and I want you to choose Link File Info, and that will give you the real goods on this image inside this gigantic multi -panel xmp dialog box. And you will see right there that we have got the name of the author, and the file number, and his URL at istockphoto.com, and so on.
You want to go ahead and scroll over if necessary and then click on Advanced. And then this is so unfriendly but this is the way it works. Here inside the Property Tree, we go down to Schema http://ns.adobe.com/tiff/1.0/. So obvious right? Go ahead and twirl that open and then down below, there are the tiff:XResolution and YResolution values right there and they are the same value because we are working with square pixels. But they are measured in 10,000ths of a point. So we have 2.2 million over 10,000 essentially. If you divide 2.2 million by 10,000, you get 220. So it is acknowledging right here that the resolution of the image is 220 pixels per inch.
Now it's not acknowledging that in English or any language any of us would understand but that's what it means. So I'm going to click OK to get out of there. So it is most assuredly 220. Why is it showing it to us up here in the Control palette that it's a 267 pixel per inch image? And by the way, if we were to re-import this image, or we were to place it right now, it would appear bigger. And you know why don't I show that to you? Because you need to see what the results of resolution are. I'm going to go to the File menu and choose the Place command. This is the command that you use to place images into Illustrator.
And then inside of your 20_images folder, you will find Sepia image.psd. Make sure the Link checkbox is on. Click Place and it just comes in like so. Move it over and you will notice that this new image is bigger. See how her eyebrows are a little higher than they are over on the right, and her chin is cut-off down here on the left, and it's not on the right? So she is much bigger. That's because she has a lower resolution. So lower resolution means fewer pixels packed in a square inch and that means bigger image. When you pack more pixels into an inch that is higher resolution, you get a smaller image.
So there is an inverse relationship between resolution and size where digital imagery is concerned. And this one is acknowledging that it's PPI of 220 but they are the exact same image. If I bring up the Links palette once again, same image Sepia image.psd, Sepia image.psd. They are exactly the same size, they were modified on the same date, blah, blah, blah. They are the same file. All right, so let's just delete that guy. What's the deal? Why is this one saying it's 267? Because it's effective resolution is 267 because it scaled down.
So it's reduced in size and Illustrator just did that automatically, just automatically transformed it to maintain the original size. And you can change that if you want to, but in my opinion it's so convoluted as to not really be worth bothering going into. It's better just to do the work in Photoshop in the first place, so let me show you how. We'll go ahead and Alt+Tab or Command+Tab back to Photoshop. I'll go up to the Image menu. I'll choose the Image Size command. Ctrl+Alt+I, Command+Option+I on the Mac brings up this dialog box. Make sure Resample Image is turned off. If you turn it on and you change the Resolution value, notice that you are going to add pixels to the image. Now Photoshop is no magician where adding pixels is concerned. It just averages neighboring pixels using something that's called Bicubic interpolation and it makes the transitions between pixels softer, which after all this sharpening work is not something that we want. And it basically rewrites every single pixel in your image.
Talk about a lossy transformation. It's rarely a good idea to upsample images to add pixels inside of Photoshop. Better to turn Resample Image off and that's definitely what I want you to do here. And notice now the difference between 220 pixels per inch, in which case we have an image that is 7.3 approximately inches wide and tall because it's a square. And if I raise this Resolution value up to 267, the size of the image drops down to 6x6 inch square. Now here is something interesting to note. You would think that increasing the Resolution from 220 to 267 is no big deal. You are just adding 47 pixels per inch in each direction. But 267x267, which is the number of pixels inside of a square inch, delivers you 71,289 pixels.
So 71 up from 48, so you added more than 20,000 pixels per square inch. That's a big significant difference in the resolution of this image. And what it means is you are going to get smoother, sharper output when you send this illustration to a commercial printer. Click OK. Because you had Resample Image turned off you won't see any change inside the image window. That's because not a single pixel was been harmed. Then you would go up to the File menu and all that's happened is the Resolution value got changed, just a little bit of metadata, just a single number got changed. So go ahead and choose Save. There is no reason to choose Save As. You didn't do anything destructive. Just choose the Save command to update the file on disk.
Now Alt+Tab or Command+Tab back to Illustrator. Aha! It knows something happened. Click on Yes in order to update the image and it looks exactly the same because once again it fit it into that same image area. If you go ahead and meatball that image here inside the Layers palette, you will see that it says PPI 267. But it said that before, right? That's because it had been transformed to fit this space. What's the real resolution? Go to Link File, go to the fly-out menu, then choose Link File Info. Brings up the big old xmp dialog box again, twirl open that tiff option right there, this guy right there. Aha! Look down there.
XResolution and YResolution now say 267 blah, blah, blah. So all you really care about is those first three numbers and they are right, yes. Click OK. So all is right in the world. Thanks to the fact that you set the resolution of the image in Photoshop before you import the image into Illustrator.
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