Understand Pixels & Resolution in Photoshop®
We've covered Illustrator, now we're gonna be working on Photoshop and going through and editing our images, doing some basic color retouching, or color correction, some retouching, filters, effects, some basic layering. What Photoshop is used for, used for all those things. What it's not used for, any type of logo creation, any type of text, posters, brochures, business cards, logos. No, not gonna use them for that, but we are gonna show you some really great Photoshop tips and techniques, and hopefully get you over into Photoshop so that you don't feel as intimidated by it as I'm sure you do. So, basics of Photoshop. Going through, got several images that we have open in Photoshop. Great thing with Photoshop, if you have an image, you open the image, Photoshop can pretty much handle it. So, I've got this photo and it's a little bit underexposed here, a little bit dark, and would like to go through and take this, be able to bring the color back. Get a little bit more saturation, maybe...
apply an interesting filter to it. Couple things we have to figure out about Photoshop first. What are we gonna use this image for? Is it gonna be used for print? Is it gonna be used for web? Is it gonna be used for output on a large billboard? What do we have? Well we had talked about what a raster image is, and a raster image is something that is made up of pixels, and all those little squares of color. Well we have to determine if we have enough pixels or squares of color in order to satisfy our end result. And what that normally translates into is the resolution of the file. How many pixels per square inch do we have, and how many do we need if we're going to be using something for print, something for web, whatever the output may be? Well we find out about that by going into the Image menu and checking out the Image Size. Now, general rule of thumb, when anything is going to be done for the web, mobile devices, any type of tablets, anything that's going to be displayed on screen on a light emitting device, we need a resolution of 72 pixels per inch. That's what we use to display on web or any light emitting device. 72 pixels per inch, that's what we need. Now if we're gonna use this for print, we need a whole lot more pixels per square inch. We need 300 pixels per square inch. Substantially larger file. And the reason why is that when we look at something on screen, we're literally seeing what it is and we don't tend to blow the pictures up. But when we try to print something, we need a lot more information in there for it to be translated into inks and then put on any type of surface. So, when I look at a file, there's a couple things that I have to know and realize about this file. First of all, how is it going to be used? And if it's going to be used for the web I need something that has enough resolution and virtually everything out there has enough resolution for the web. But not everything has good enough resolution for print. So, print resolution, 300 pixels per inch. Web resolution, 72 pixels per inch. So, can I actually use this for something else if my file is quite small? Can you use it for print? And the answer is maybe. Which is a great answer to start off with. Here I'm trying to learn Photoshop and the answer is, maybe you can. Basic thing with Photoshop that you have to understand. When you open up an image, you have a fixed number of pixels in there. And these fixed number of pixels make up the entire image. So, if you have a higher resolution file that means you have more pixels per square inch. The pixels are smaller, they're closer together, the resolution is higher and therefore generally better detail. When you have a lower resolution file, that means lower number of pixels, like 72 per square inch. The pixels are larger, their resolution is lower and the quality is lower because you have bigger blocks of color. Can I go in and can I swap the resolution for size? And the answer is, well you can. If you go into the Image menu under Image Size, I see that I have an image that is, I'm gonna change this to inches so it makes a little bit more sense, so about six and a half by four and a half inches, and the resolution is 300 pixels per inch. So I could very easily use this for the web because I could always go down in resolution, but going up in resolution becomes a little bit tricky. So here's an interesting trick if I want to be able to go in and not do any damage to my Photoshop file. I want to go in and I would like to resample my image, and when I turn off my Resample image, you'll notice that my width and my height and my resolution are now all linked together. Which means, if I go in and I change the size of my file, or I change the resolution of my file, I'm not actually stretching the file or making it do things that it shouldn't be doing. I have a fixed number of pixels, and there is my pixels, 1,950 by 1,299. With a total file size of seven and a quarter megabytes. When I turn off the Resample and I go in and I set my resolution down to 72, I have the exact same file size, and the exact same number of pixels. What I have done is keeping all of these linked together, I have gone in and made a much larger file with a much lower resolution. And my analogy that I use for this is if you blow up a balloon, it's the same balloon but the more air you put into it, the larger you stretch it, and the thinner it gets. It's the same amount of balloon. But as you put more and more air in, the more you stretch it the thinner it gets. The exact same thing is true with an image. So if I take an image and I stretch it larger and larger, and larger, I'm taking a fixed amount of information, stretching it over a larger area. The more you stretch it, the resolution goes down. Same content stretched over a larger area, it gets thinner, plain and simple. The opposite is true. If I have an image that's 72 pixels per inch and you open it up and it's like, I can't use this for print. Well you can. The only problem is is that I couldn't use it at this size. It's big and it's very low resolution. But with all of these linked together I could take my resolution and I could make the resolution higher, which is reducing the size of the image, and when I reduce the size of the image, I'm packing more information into a smaller space. The resolution then is going up because if the opposite is true, if I stretch it and it gets thinner, if I push it back it's gonna go ahead and the resolution is gonna increase. So, yes I can use this in varying forms here, but I'm going to sacrifice size for quality. That's how it works. So, right now if I use this for print I can use it at six and a half inches, but if I use it for the web, which by the way we never ever use inches for the web, it's always in pixels, and the reason why we always refer to this in pixels is because no matter what we do for the web it is always a given when somebody tells you X number of pixels wide by X number of pixels high, that always means at 72 pixels per inch. That's why. So, I can use this for the web. This can be really huge. If I want to use this for print, I can, but I'm gonna sacrifice the size. Another analogy is, you have $100. You can have one $100 bill, or you can have 100 one dollar bills. It's the same amount. One you have a lot more quantity, one you have a lot less quality, quantity, it all equals the same thing. This is the same. I can stretch it over a larger area. It becomes thinner, lower resolution. I can also put it back together, compact everything, higher resolution. So I can have that trade-off. What you can't do is you can't go into a file here and take what you have, and then go in and make this file larger just by making it larger. So I turned on the Resample here and somebody needs this for print, and they're like, "Oh I need it for a poster," and it's like, I know Photoshop just well enough to get into trouble. This is licking a light socket kind of trouble, okay? So I go in and it's like, oh I learned this great trick. Watch, I'll take this Photoshop file and I'm gonna make this 24 inches wide, and it's like, look, everything's great and as long as I can click OK, it's okay, right? Why do you think they have the OK button? That means it's okay. No it's not. What you've just done is you've just taken a seven megabyte file and made it a 100 megabyte file. Where did all that information come from? Well it faked it all. You run out of money in your checking account, you whip out your checkbook and just move the decimal two points over, and all of a sudden you have more money. People are like, well that's stupid. Yes, and when you do something like this in Photoshop, when you go in you can't make an image larger without sacrificing something. So I've just gone in and I've made it six and a half inches. Now it's 24 inches wide. Well I could take any image then and just blow it up. You can't. Because I have a fixed amount of information, and what you capture with your device is what you end up with. You can only go in and make it smaller without sacrificing quality. So if I go in and I just made this bigger, it's going to blur everything, and you can see just how blurry that is. The technical term is interpolation. It's looking at all the other pixels around it and it's filling it with just basic, random pixels that are around it and it's blindly filling it in. That is never gonna give you a better image. It's bigger, it will never be better. So, if you do want to have a higher quality image, take a larger higher quality image. You can always reduce it down and make the quality less. You can never make the quality better or make it bigger and keep the resolution the same. Plain and simple. So as you shoot your images here, you have your phones, you have your cameras, and you have the two and four, and eight, and 10, and 12 megapixel cameras. That is more and more pixels per square inch. The more pixels you have per square inch, the more information you have, the more you can deal with that information. Low resolution file is always gonna be low or lower. High resolution file, you can always dumb it down, you can't make it smarter. That's the one thing with Photoshop. You can make it look slightly better but you can never create something from what you don't have. So, with that in mind, that's one of the things to understand about the file.