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Adobe InDesign CC - Essential Training

What is Effective PPI & Image resolution in the InDesign links panel

Daniel Walter Scott

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Hi there, in this video we're going to look at what image resolution is, or DPI, PPI, effective PPI. Basically it comes down to the quality of your images. Let's go and do that.

So image resolution might have come up in your world before, and you might be like, "Ugh, I can't understand, or maybe I don't." Maybe you've never heard of it. So, let's have a quick little look at what it is.

Resolution is basically the quality of an image. I'm going to click on this background image here. I'm going to go to my 'Links' panel. If you can't see 'Links', go to 'Window', 'Links'. What we're going to do is, you might be able to see it already, but I don't have mine activated. See this little arrow here, it says 'Show/Hide Link Information'. I'm going to make mine go up a little bit higher just so I can see a bit more of this link information. You can twirl it down, make it bigger. It just gives you information about the image. So there's the name, it's a JPEG, it's on page 1, it's RGB. What we're really looking for is this one, the major one, the 'Effective PPI'.

PPI is an acronym for Pixels Per Inch. If you've ever heard of DPI, or Dots Per Inch, it's exactly the same thing. Just a new way of explaining it, pixels instead of dots. And we've got targets to hit. So the effective PPI, maximum, should be about 300. That's going to give you amazingly beautiful, crisp, clear image when we print it. And the lowest that we can go is variable. So, it comes down to what its purpose is. If this is going to be printed commercially through an offset printer, and then put out in our display case at our showroom, then we want it to be as close to 300, or above. You can even have 1200, and that's fine, there's nothing wrong with that. Above is good, below is where it starts getting into the gray area.

So 300 is the target, it's totally just a made up number that looks really good. Some people use it like some sort of carved in stone, can never be changed number, but really, if you're close to 300 like this one here, it's 291, I would not care. It is probably to impress people that they might-- I'll be going to a red kind of color now but if we were honest, we've all printed stuff below quality, and nobody's noticed the difference. So, it's how low can you go? And what really happens is it's depending on how big you stretch this image. This image, you can see, its actual PPI is 300. So here is a 300 DPI image, or PPI image. Now I just stretch it a little bit bigger to cover the 'Bleed'. So I made it just a teensy bit bigger, so it reached over this 'Bleed' here.

So, let's look at an example that won't work. I'm going to delete this guy in the background temporarily. I'm going to go to 'File', 'Place'. And I've got an example in '03 Newsletter', grab that one. And let's go to 'Image Resolution Example'. I'm going to bring it through, and I'm going to bring it in-- I've just clicked it once and that's come in. And it says it is 72. So, if going to a commercial printer, it's not going to work. It needs to be at least 300. But it looks okay on screen, so if it were going out to a screen as in, it's going to be emailed, or downloadable from your website, 72 is just a fine size. I'd like it to be a little bit higher but the minimum is 72 to look okay on those screens. On a retina screen, like this MacBook Pro I've got in front of me, it will look a little bit pants, but-- I got to stop using the word pants, it's UK slang for bad. They're kind of pants, not bad, anyway.

Back to resolution. So it is 72 Dots Per Inch, or PPI, Pixels Per Inch. So it's going to work for screens, but it's not going to work for print. But let's just say, "Let's just make it bigger." I want to use it for the whole cover, so I'm going to make it quite big. I'm going to make it nice and big, so it covers the 'Bleed'. I'm going to trim that up there. It's looking okay, right? Looks kind of fine on my screen now, might look okay on your video but it will print really badly. You can see, if I select on it, the effective PPI is 30 now. Why is it changing? It's because I'm scaling it out. Watch the effective PPI as I keep scaling it up. Scale it up, there it goes, 28. It's kind of stretching those little pixels if we zoom right in.

It's actually made up of little squares. That's what resolution is, or Pixels Per Inch. These are the pixels, and how many pixels are in an inch? At the moment there's only 28 in an inch. You need a lot more dense pixels for this to work. I'm going to zoom out. You can start to see now, it's looking a bit red around the outside, pants even. So the main thing to look at-- don't worry about the quality of the image that came in first. Back in the days of yore you had to make sure everything was 300 PPI before it came in. What you can do now is, you're just looking at effective PPI. Ignore this number here, whatever is here. So if this is going out to commercial print, this is so far from 300. That is not going to work at all.

Now, what are the boundaries? Say I do want to use this commercially, I'm going to scale it down. You can see, it's still too little. So if I want to use this in commercial print and I want to use it at 300 PPI you can see, I'm going there, 138. Might as well move it across so you can see it closer. Getting smaller. 227. 312, close to it. So that now is the right resolution to be printed. Unfortunately, it's teeny tiny. So if you're downloading images from the internet you've got to make sure they're really big. So at least when you scale them down, you get close to 300.

How low can you go? Now this is total personal preference. Now the rule is 300, but I know if it's a good quality image from a stock library site, you can get down to about 180. 150, if you're really sneaky, and it will print fine. I probably wouldn't do this for the front cover because it's such an important part of this document, but say it's an image on page 2, and it's just a small image, and the resolution is about 180, nobody will notice. Again, it really depends. If you're trying to sell Bentleys and you've got some low quality images that are just slightly off, I'd be looking for 300 and above for resolution. But in the true day-to-day world, 180 works just fine for me.

And to recap, if you're working on screens, that means it's going out via digital means, it's going to be emailed, or downloaded from a website, 72 is the minimum. A lot different, because screens deal with resolution a whole lot better than when it's printed physically. So if that's the case, I can have this all the way up at 54, not quite there, but we're getting close, 59. Come on, Dan, you can do it. Okay, 71, 72, that is fine if it's a physical size, it's going to be a digital download.

So in summary, just make sure your effective PPI is between 72 and 300, depending on its purpose.