Print Vs On-Screen Resolution
I loved being in this segment to talk about pixels and resolution because it is a grossly misunderstood topic. And people just don't understand it, and the cost of not understanding it can be really big, actually. You can really destroy your work or your images if you don't know what you're doing with it. So this is an important segment. So let's talk about, what we talk about with pixels on a screen, what does that mean? 'Cause they're different. And this is where it gets really confusing. On a screen, we don't have inches. We just have pixels, right? A screen displays a certain number of pixels across, and a certain number of pixels up and down. So if we have an image that measures like this, 400 pixels across like a square, on a screen, it's going to be 400 pixels. It's just gonna take up 400 pixels. Now, on a screen that only displays 1,000. Let's say this example, the picture's 1,000 pixels. This example was a 400, but, let's say that that same image is 1,000 pixels. 'Cause 400 wo...
uld be like maybe a phone screen. So we're gonna look at a laptop. So let's just pretend that this image measures 1,000 pixels across, and let's pretend that this laptop on the left measures 1,000 pixels, the display, it displays 1,000 pixels on the screen. So that 1,000 pixel image would then fill the screen, right? That makes sense. Now that same 1,000 pixel image would look half as big if you had a different laptop with a screen display set to 2,000 pixels. That same 1,000 pixel image would now only take up half the screen, so it would actually look smaller, but it's the same size. That's where it gets really confusing. And I remember when I was learning all of this stuff so long ago, I mean it was really very long ago, before DLSRs and everything. Before I had ever, before like normal people, regular people had them. It was very confusing, and I was reading this book and it was trying to explain resolution and pixels and I just remember being like, this does not make any sense, and I actually tried, trying to understand it, I actually, whatever image I was looking at on my desktop, I actually picked up a ruler, like a print ruler, right, and I held it up to the screen and I'm like, I don't understand why I feel funny right now, but I'm trying to measure this image and I don't get why this doesn't work and it doesn't make sense but I'm not sure why. And because there's not inches on screen displays, of course, the physical screen itself has dimensions that you can measure in inches, but the actual graphics, if we're talking about anything displayed on a screen, there are no inches. My husband is a web developer and he wouldn't know what to do if I was like, I'm gonna give you an image for the website, and it's gonna be four inches. He'd be like, that doesn't mean anything to me. He would need it to be 400 pixels, or 873 pixels, or whatever, it's all specific and all about pixels when we're talking about screen. Print, on the other hand, is a whole other ballgame, and in print, we have this whole thing called resolution. Which refers to the number of pixels per inch. So resolution is a function that depends on print size. This is something people really miss. And they will say, this image is low resolution, or high resolution, and what they mean is it has a lot of pixels or it doesn't have a lot of pixels, but the missing part of the equation is depending on what they want to do with it. You can have an image, for example, when I was designing these business cards recently, the images I was given were of course, small, and the person who sent them to me downsized them so that he could email them all in one attachment. And I of course wrote back right away and was like, oh, no no no, I need the original. And they're like, these are the originals, they're just smaller, and I'm like, no, I need the unedited originals, like not resized. And it took a while to get those files, so in the meantime, I just went ahead and started with the design to save some time, and actually, it turned out that the size of the images on what I was designing was actually gonna be so small, that it actually worked with the small images. So even though they were resized, I had enough pixels to use them at the size I needed. So it does depend on print size, and we'll take a look at that in more detail here, but basically, you either have enough pixels that the picture looks good, or if you don't have enough pixels, you will know it, and the picture will not be good, and you'll know that you do not have enough. It may not be quite that dramatic as in this example, but it can be, it can look like that. So how do you know if you have enough? Well, there is, of course, a certain target that we would like to hit. And for print, that target we want to aim for is 150 to 300 pixels per inch. People really get hung up on these numbers. And there's good and bad about that, but that's really the target area. Anything lower than that, you're gonna start getting that kinda pixel-y mosaic look. Anything more than that, is a waste of space. So, if you, for those business cards, for example, I didn't need them to send me a 25 megapixel image to appear on a business card. But they probably don't know much about image size, so I can't really tell them, well size it down, but not too far, like, I would rather they send me all of it and I can throw off what I don't need. We have a question. Gabby.
How do you know how many pixels a picture is?
How do you know how many pixels are in a picture? That is an excellent question. Your camera should be able to tell you. So in your settings somewhere, which we'll look at in a moment, there's a place where you can choose the setting that you want, the size that you want. Pretty much all the cameras have their high size, their high setting, and then you can scale it down if you want, which I never recommend. You always want to leave your camera pretty much on the highest setting, because you can always throw away pixels, but you can't reinvent them after the fact. Not well, anyway. Another way that you can tell is, once you get it down on your computer and you open it in Photoshop or Lightroom or any kind of software program, or even if you look at it in Finder or Windows in Explorer, it should tell you, like when it tells you the general file information, it'll usually give you pixel dimension. But it's never gonna be, well, straight out of the camera, it's probably not gonna be something clean and nice like 400 x 600. It's gonna be like 5, by some other weird messy number. So that is gonna just be a native thing from the camera. Does that make sense? So whatever if you have a 20 megapixel camera, or a 10 megapixel camera, the camera will determine how many pixels it can capture and what the actual image dimensions are. We're gonna get into that in a little bit here. So that's our print resolution target is we wanna end up with 150 to 300 pixels per inch, but what does that even mean, and how do we even know? How do we get from an image that's 5,783 pixels wide, how do we know if that's gonna 300 pixels per inch? Well, I like to use this analogy, and I've used this before, so if you've seen one of my other image resolution discussions here, this may look familiar, but this is like the best analogy. And really, not just because it's peanut butter and that's delicious, but because I think it really makes sense. So, here's the thing. If we think of pixels like peanut butter, then this is a very easy concept, okay? So let's pretend that we are hungry, and we go to the kitchen, and this is all the peanut butter that we can find. That's it, that's our last peanut butter. So we have to decide how we're gonna use it, 'cause it's only a spoon. So, we have this nice, I would probably just eat it like right off the spoon, hrum! But let's say we're fancier than that. So, we could take the one spoonful of peanut butter and we could put it on one nice little Ritz cracker or something, and it would be thick, like we could scoop it onto that Ritz cracker, all the peanut butter on one tiny cracker, it would be really thick. That would be similar to how a high-resolution print might be, if we talked about this print target being 300 pixels per inch is like the optimum, that's like the dream, then this cracker with this peanut butter would be really thick. That's a lot of peanut butter on one little cracker. So that's like a high-resolution picture, 300 pixels per inch. But we could also take that same amount of peanut butter and we could spread it out into a thinner layer, we could spread it out on, let's say, a tortilla or something. So the tortilla's gonna be much larger, much bigger surface area than the little bitty cracker. The same amount of peanut butter, on that big tortilla, is gonna have to be spread more thinly to cover the tortilla. That's how resolution works. It's really that simple. You've got a set number of pixels, or peanut butter, and you're either going to take all those pixels and put them on a cracker, and print like, a wallet-sized photo, or you're gonna try to make, let's say, a poster. And the question is, do you have enough peanut butter to smear it all over that poster or that tortilla without running out and having it be so thin that you don't even taste it anymore? Right? That's all there is to it. So, the smaller the surface area you're trying to cover with your established amount of pixels, the thicker, the more pixels you can have per inch. So that's how it works out. You don't have to actually do the math. Computers and everything does that for you, and we'll get there. But let's take another look. So now we understand the concept of like, peanut butter, and it's either gonna be spread really thin, or it's gonna be all in a big thick chunk. Let's look at that now with actual numbers and pictures and stuff. So if we have this image here, that, let's just for simple math, we'll just say that it measures 400 x 600. Obviously, out of today's cameras, they are much larger, but I don't like doing that kind of messy math, so we're keeping it simple. So let's pretend that this image is 600 x 400 pixels. So it's 600 pixels across, 400 pixels up and down. Those are the pixel dimensions. Now, it turns out that pixel dimension (clears throat) and the image dimensions is different than print dimensions. So we can have that same image that measures 400 x 600 pixels, and then, if I said, okay, well if we didn't know yet what size we were gonna print it, I could still tell you, what size would that print at? And you'd be like, I don't know. How big does 400 x 600 pixels print? Depends what you're trying to print and what resolution's gonna be acceptable. So if we do the math in this case, a 400 x 600 pixel image, if we print that at 4 x 6 inches, how many pixels would we have per inch? In the microphone. You can do it, it's simple math, even I can do it. So I didn't wanna put anyone on the spot.
Would that be 100?
Mmhmm. Exactly. So we would then have 100 pixels in every inch. So we're taking, that's our peanut butter, we've got 400 x 600, that's the amount of peanut butter we have. So if we're only gonna spread it across a 4 x 6, which is pretty small, I mean it's kinda medium small, but, we would end up with 100 pixels per inch. Which is less than our target, but obviously, we would normally be working with much higher numbers. So let's think now what if we take those same 400 x 600 pixels, but instead of a 4 x 6, let's say 2 x 3. Ooh. Now this is getting tricky. (laughs) So we're making our, we're basically going instead of like a small tortilla, we're now going for the Ritz cracker. So what just happened to our resolution?
I believe we went to 200.
You are correct! (laughs) So our resolution just increased. And if we wanna care about all the specifics, the resolution doubled, because we halved our size. But we don't even have to worry about that. All we have to know is the print size got smaller, so the resolution got up. It's like we took all that peanut butter and instead of the tortilla, we scraped it all off and put it on a little tiny cracker, it's gonna be much thicker on the cracker. Okay, so then likewise, what if we take that same amount of peanut butter, but now not a cracker, now not a tortilla, maybe now like a huge pizza? I don't know, what's bigger? A big pizza, let's say, an 8 x 12. Now we want to take those same 400 x 600 pixels and print them as an 8 x 12, we're gonna be down even smaller.
50. Yes. So as the physical size gets larger, the resolution is getting smaller. And as the physical size becomes smaller, the resolution would then go up. So I really like the peanut butter analogy because that's how peanut butter would work. (laughs) And I don't know about you, but I have definitely, my husband and I both love peanut butter, and when we get to the bottom of the jar we're like, awww, you left me with like one useless bit of peanut butter. (laughs) I guess I need a cracker or a tortilla or what could it go on? I don't know. Or I'll just eat it, but that's a whole other story. Okay, so, if we look at this here, we can see that that same number of pixels could be distributed in such a way that it could print, at different sizes, the same number of pixels. But you can see that, depending at what size we print it at, the resolution would actually vary quite a bit. And you can see that in this example, we'd really be best at printing that as a wallet, only 2 x 3 inches. We don't have enough pixels in this example to pull off even a 4 x 6 print. It would look pretty bad. 50 pixels per inch, or 100 pixels per inch would be pretty bad. But that's really just a guideline. 150 would be like your home printer, and you can get away with a little bit less than that, it's not like a magical number at 150, but you just basically don't wanna be getting down so low that you could play checkers on your (laughs) on your print. But if you were having something sent to a commercial printer, then you would notice it even sooner, so you really wanna be around the 300 mark. But also, like I said, the computer handles all this for you, so you don't have to totally worry about, I didn't size this, or. There are things you can do to avoid problems, and that would be one, have your camera set to the highest size that you can. Pixel size, so however many dimensions, and we'll talk about that here in a minute, but you wanna keep it set there.