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73 - What is the difference between RGB and CMYK in Adobe Photoshop CC


Questions & Comments

XINJUAN DENG - 4 months ago

so we dont need cmyk at all, right???

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Video Transcription

Hi there, this video is all about the differences between CMYK and RGB. So why do we need two of them, and what are they? Basically there is a way of mixing colors that your computer can do, using red, green, and blue, that's why it's called RGB. And it can mix those three colors together to make all of the colors you can see in front of us, in this kind of like color explosion. The trouble is your commercial printer or your printer sitting on your desk. You pop it open and have a look, it uses a different group of colors, to try and mimic what we've got here on the screen. It uses CMYK, which is cyan, magenta, yellow, and black. 
You've probably bought lots of those cartridges in your life. The big difference is that RGB has a secret ingredient. It has light, so your computer screen, looking in front of you, has light shining out of it; luminance. So it's able to achieve different colors or more colors, whereas CMYK has to deal with a bit of plain old white paper. So there's no light coming out of it so the colors can't be achieved. You've probably seen it before, looks good on screen, hit print. Your poor printer turns it to mud, because it just doesn't have light coming out of it. So it can't achieve some of those really strong rich colors. 
Let's have a look at the difference between the two, so I've opened up, 'File', 'Open', and in your 'Exercise Files' called '13', there's one called 'RGB vs CMYK'. This one's an RGB. How do I know? You can see in the tab here, it is RGB. And that's how most things are going to come to you in the world. Digital cameras, RGB, downloading something from the internet, RGB. Let's have a look at it in CMYK. 
Let's go to 'Image', 'Mode, and switch it to 'CMYK'. Ready, steady, go. I'm not sure how much of a change you can see in this video, but I'm going to go undo. RGB, CMYK, RGB, CMYK. Great, not great, great, not great. So why would you end up in CMYK when it doesn't look as good? It's when you're going out too often to a commercial printer. So you've been asked to do a print, say it's one of your amazing photographs that you're getting printed commercially, or you're working more as a designer, and you're getting an image ready for a magazine. They're going to say, we want CMYK, please. So what you're going to have to do is open up your image and switch it to CMYK. And now save out a JPEG and give them that. 
So it has kind of a really specific use case, it's physical printing. You might be sending it to a sign writer. As part of their specifications they might say, it has to be this big, this much resolution, and it has to be CMYK. So that's how to convert it. The trouble is there's not as many colors, so often I'll have two versions, because so much of things we do today have dual use, especially for me, maybe as a designer, I'm doing stuff that's going to print, but it's also going to be downloaded from a website, or uploaded to the website, or going to social media, banner ads, all sorts of stuff. So if I'm going to convert this one to CMYK to send it to print, it's a one-way street, right? 
So if I go to 'Image', 'Mode', and I go 'CMYK', and then I go back to 'Mode', and go to 'RGB', watch. The colors just don't come back, it's a one-way street. So once you've gone to CMYK, you can't, like, convert it back to RGB, it's still going to look flat. It is RGB technically, but you've lost all those colors. So you might want to do a 'Save As', so you've got two versions. I'm going to go to 'Edit', 'Step backward' until it was legitimately RGB still. Nice and colorful. 
So I'll just go to 'File', 'Save As', and I'll add the words CMYK. So I know it's a slightly more washed out version. It's, I guess a funny one to understand, but I guess I don't want you leaving this course, because it's only a matter of time before it pops up, that you need to understand what RGB versus CMYK is. Let's talk about two use cases, and then we'll move out of this video. Let's talk about the first use case. Let's say I'm a photographer, I'm working on this photograph that I've filmed, that I've shot of the color splash here. Done my tweaks, done my levels, done my masking, all looks great, and now I've been asked for it, from my designer, they want in CMYK, or from a print shop, they want it in CMYK. 
So what I'm going to do, first of all I'm going to make sure I've got a RGB version, because remember, it's a one-way street. So I'm going to save it as, I'm going to put this onto my desktop. This one's going to be called 'Color Splash RGB'. So now I've got that one, right? Now I'm going to go down the one-way street, for the one that Bob, the graphic designer needs. Lost all my colors, there's just no way of getting them, because paper just doesn't have that illuminance. So now we'll go 'File', 'Save As' again, and this one's going to be my CMYK. So I've got two versions of it, right? One of them is the one with a fuller color, and one of them without it. So I'm going to send this one to Bob because that's what he asked for. 
And the other use case, and the more typical one is, let's say I am this photographer or graphic designer, and I've got this, however we got this image, this is my original, no, I want the original a RGB one. So one with all the colors. So I've just got the RGB one open, and now I need to put this in to, say it's going to go into some social media, I just use this RGB version. Copy and paste it into the file I'm working with, but let's say we're doing something different. Let's say we're going to physical print and digital. So I'm going to load this into InDesign to make our little brochure. It's going to be printed off, and it's going to be both in the reception. So physically, so I need CMYK version, but also it's going to be downloaded from the website, emailed around, it's going to be used as a PDF. What to do then? Do you have two versions? A print version of a magazine and a digital version. No. 
What tends to happen these days, there will be purists out there who don't like this method, but for me, in my experience, what you end up doing is, just use the RGB document wherever it is, it doesn't matter if it's InDesign, and it's going to print, just leave it as RGB, and let the printer change it on their side. So that you've got one copy, one PDF that you've made, that's got all the great colors in it, it makes life easier for you. And what ends up happening is, modern printers, so the ones that are going to physically print and bind your magazine, they have some pretty cool rip software and kind of pre-processing software. It actually extracts probably more color from your RGB, and they have a really good conversion process to CMYK. Better than what just Photoshop's going to do here. 
A lot of printers will use more than just cyan, magenta, yellow, and black. They'll have a bunch of extra colors and try and match RGB a little bit more. So I just grab this image, dump it into InDesign or Illustrator, into my graphics, and just leave it as RGB, send it to the printer, make sure they know. Say, "Hey, I'm just leaving as RGB, can you convert it for me?" They might come back and say, "No, you need to go the traditional route, and make sure it's CMYK before it's all in InDesign", but most of the people would just take your RGB, print it off, and it's pretty amazing what they can come up with. Some pretty good matches to this RGB. 
Are you a little bored of RGB and CMYK? If you've made it this far you'll get a gold star. Go draw one on your hand, that is you for the day. You hung out and watched this whole video. As a little surprise, well it's not much of a surprise. 'File', 'New'. One thing to note is, when you're making a new document, see down here, Color Mode? You can pick RGB and CMYK before you get started, but if you pick CMYK now it will always default to CMYK. So just make sure color mode's RGB to get started. Pretty much everything, unless you're going to print. And then they ask for it. Enough Dan. Let's get into the next very exciting video about resolution. Super important, just as nerdy.

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