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For more information, please see full course syllabus of Adobe Photoshop Elements 11
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Image Size, Canvas Size, & Resolution

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Lesson Overview 0:07
  • Image Size & Resolution 0:58
    • Megapixels
    • File Size
    • Resolution
    • Image Size
    • Changing Document Size Only, Maintaining Proportions
  • Re-Sampling 8:09
    • Re-Sampling to Maintain Proportions
    • Re-Sampling to Distort Image
  • Canvas Size 16:16
    • Canvas Size
  • Sizing for Print & Web 21:52
    • Sizing for Print & Web

Transcription: Image Size, Canvas Size, & Resolution

Hi, everybody--Mike Brown back with you; welcome back to's Adobe Photoshop Elements Beginning and Intermediate course!0000

We're about to get into working on the images in the Expert mode--all of the various distortions and changes and layers and compositions and all of the stuff you can do, but we need to talk about three important things before that.0006

First of all, when you have your image and you're working on it, you need to be saving that image, and you need to save it frequently.0021

So, we have to talk about how to save it, where to save it, and the formats--which is the second thing--that you can save your image in--why we do the various formats--and the third thing we need to talk about is image size (which we're going to do in this lesson), canvas size, and resolution--how they all work together, how you can increase the size of an image, decrease the size of an image, how you size it for print, how you size it for Web.0028

Then, we go into the formats and saving.0055

Let's get started!0058

Here are some descriptives; we're going to quickly go over these, because they all apply.0060

Megapixels, as you always know, is the number of pixels on your camera's sensor.0067

That is the horizontal times the vertical pixels on the sensor of the camera.0078

Your file size, when you open up an image in Photoshop Elements, is actually three times the megapixels, because your sensor shoots a red, green, and blue channel, each with the same number of pixels, so the file size will be three times as big as the megapixels of your camera.0084

Resolution is simply the number of pixels per inch or centimeter, horizontally or vertically, in your image.0103

Now, image size--that is document size--is the length and width of the image, independent of resolution--it's merely document size.0115

Let's take a look at what document size looks like, how we change it, and maintaining the proportions (in other words, not distorting our image).0131

What we're going to do, to do image sizing: we go to the Image menu to Resize, to Image Size Box, and up pops the Image Size box.0141

Let me actually go to an image, so we can work with an image; image resize, image we are.0154

Here is the Image Size box, and there are three distinct areas in a dropdown menu; let's go through those.0161

The first box is the pixel dimensions and the file size of your image.0169

This image is 3000 pixels wide, 2000 pixels high, and it should be 18 megabytes, but the computer trims just a little bit off when it opens it up in Elements, and it's actually 17.2 when it opens--approximately 18.0175

Now, for 3000 wide and 2000 high--that is the number of pixels we have--at 200 pixels per inch, either horizontally or vertically, obviously, the width--if it's 3000 pixels wide by 200 per inch...3000/200 is 15 inches--very simple.0193

Accordingly, the height is 10 inches.0216

That is the document size, and these three relate to each other; if you change the resolution, normally you would change the width and height; we'll talk about that.0220

Below that are three checkboxes, and by default, they are checked: Resample Image (in other words, add more pixels and make it larger or take away pixels and physically make the image smaller--not changing the document size, necessarily--making the image physically smaller and changing the file size).0230

We also have Constrain Proportions; that way, if you resample your image and change a single dimension, the other dimension will automatically change, so that the image still looks the same, whether it's larger or smaller.0252

Scale Styles is important if you're working with graphics and effects; if you have drop shadows or glows or bevels, things that you put in as effects don't automatically change if you resize an image.0265

Therefore, if you're resampling to add or subtract pixels, you need to check the Scale Styles.0280

In this case, we don't have any, so it doesn't matter, but it's to automatically do that.0286

Now, don't worry about Nearest Neighbor, Bilinear, or Bicubic; the two things you need to deal with when you're resampling, or making an image physically larger or smaller in file size: if you're going down or reducing the image, you want to use Bicubic Sharper, because the computer throws away some data, and you want to sharpen it back up.0290

When you're enlarging an image, and you're opening up the spaces between the pixels, the computer is filling that in, and it needs to smooth it, because otherwise it would look kind of degraded.0316

So, enlarging--you use Smoother; reducing--you use Sharper.0328

Now, let's go back (oops, I went back to the descriptives); we want to just change the document size only; this would be for printing--maintaining the proportions and not changing the file size: Image, Resize, Image Size.0333

OK, and (oops, I want to go back to the picture again--sorry) Image Resize...Image Size; here we go.0355

I would like to print this image out on an 8.5x11" piece of paper, and I don't want to either enlarge it or reduce it; I just want to change the document size.0363

If I uncheck all of the boxes (and, you notice, the pixel dimensions are a lot), notice, I can't do anything with them; no matter what I do in this document size box, it's going to still have 3000x2000; it will just change the document size and the resolution accordingly.0380

We want to go inside an 8.5x11, so I want to change the width to 11, and notice that the proportions are 7.33, still 2 to 3, and to accommodate the fact that the pixel dimensions are still the same and the file size is still the same, we made the document size smaller, so the resolution had to increase.0399

It went up to this odd number 272.27.0424

If we click OK, we're ready to print this image out at 11x7.333, which would fit in an 8.5x11 paper.0428

We're going to reset; the way you do that is Option on a Mac/Alt on a PC, and it will change your Cancel button to the Reset button and brings it back to 0; let's uncheck everything again, and let's go up; let's say we want to print this image on a 20x30 panel.0438

If we go up to 30x20, the proportions are the same; the resolution is cut in half, because, once again, height times resolution has to be 2000; height times width has to be 3000.0459

That is how you change the document size without changing the file size.0474

There we go; we'll cancel out of that; let's go back to the descriptives.0480

That is changing the document size only, maintaining everything else.0486

If we want to resample and enlarge the image to a different dpi, or a different size, or contract the image to a different size, and maintain the proportions--let's go back to that image: Image, Resize, Image Size; we want to put this out to the Web on a website.0490

Typically, monitors are somewhere between 72 and 95, depending on PCs or Macs, pixels or lines per inch; and in the case of this Mac, if you looked at my system preferences, you will see that I have all sorts of choices; I can have it as much as 1050, which is the entire vertical, or down to 800--all sort of options there.0514

Other monitors today are higher resolution or lower resolution (older or newer monitors); it's best to try to pick a medium point.0542

If you're going to go out to the Web, we'll go to Image, Resize, Image Size; now, if I want this thing to be...a typical website is approximately 800 to 900 pixels wide, so this image--I don't want it to be any bigger than 800 or 900 pixels, and right now, it's 3000, and also, the resolution is 200--it's absolutely mammoth, and it's a huge file size--we need to take it down.0550

So, what we're going to do is to leave the checkboxes up so we can resample it; in other words, we're going to make it smaller and throw away data; constrain the proportions so it doesn't distort the image; and we'll leave the Scale Styles on, as well.0580

We're also going to go with Bicubic Sharper for reduction.0593

Now, notice that the Pixel Dimension box is now active; the first thing I want to do is do the resolution--I'm going to go down to 72 dpi--that is the typical resolution that you would do if you're preparing any image for the Web--72 dpi, and we know that the websites are...I'm going to go full-width on a website--maybe the website is 900, so I'm going to make the width 800 pixels.0598

Notice, it has allowed me to change the resolution and the width in pixels or document size, and look: it was 17.2 megabytes; now it's down to 1.22; we took it way down.0624

We click OK, and notice that the image looks just the same; when we zoom it up to 100%--right now it's at 100% magnification, and look: it looks just fine on the screen.0638

If I open up my own website--I'll go to the website right here, and you notice that it's just a little over 800 wide; let's go to Facebook...Facebook isn't a good place to go for that...0652

Here is another website I did for a school; now, we have a lot of excess space, but you see the width; I'm going right back to the width at the bottom, and again, it fits inside that.0670

That is roughly the way you would make an image for the Web, and it looks great on the screen; now, if we zoom it up, you see that it's very highly degraded, because it's a very small file.0682

So, I'm going to do Command/Control+Z and let it go back to the original file size.0693

We're going to go back to the descriptions; this is how you resample to go down.0699

Now, let's also take a quick look at going up.0704

Image, Resize, Image Size; rule of thumb--we're going to leave our checkboxes checked; this time, we're going to do Smoother for enlargement.0709

We went way down in size, from 3000 pixels to 800 pixels; we went about a reduction of almost four times when we reduced it, and the image still looks great.0719

If we were to go up four times, it's not going to look really good at all, because the huge amount of space that will appear between the existing pixels that the computer will have to fill in--it's going to look really bad.0733

So, the rule of thumb is approximately 15, maybe 20 percent increase; no more.0746

In this case, if we want to resample, constrain proportions, and go up, let's say 20%, that means 20% of 3000 is 600 pixels, we would go up to 3600; proportion changes--it's now an 18x12 image, and it went from 17 to 24 megabytes.0755

Bicubic Smoother for enlargement; let's go ahead and zoom it up, and let's see how it looks; let's go look at that rock over here.0775

Now, we're going to go down and bring the rock back in and come back up; look at those two; down; it looks pretty good--it's not too bad.0787

Now, we're going to do Window, History, I want to go back to the...we're on the Open; OK.0797

20% works pretty well with the Smoother; let's go back here and go back to our descriptions.0804

That is how you resample (oops, I didn't mean to scratch it--just do that) to maintain proportions--either down or up.0811

Leave all of the checkboxes.0824

Now, resampling to distort an image: you might do this occasionally, and I'll show you a situation where I have been doing it, and I'll show you how to do that.0826

We have this shot right here, and you notice that it's actually not as horizontal as the previous image; let's take a look at that one--see how this one is stretched and this one is not?0836

This was shot with a 4x5 film camera, and I want to make it the 2x3 proportions, and it's the kind of a scene that I feel that, if I stretch it a little bit, I mean literally distort it and stretch it, that it's not going to hurt it.0849

Now, there are two ways to do this; we'll talk about a little bit more on the canvas size.0866

The first way is: I'm going to do Image, Resize, Image Size, and what I want to do to start is: I'm just going to go ahead and make this 30x20 (oops, I didn't want inches; I meant 30 inches), and it's 30, but it's 22; or, if I make it 20, it's 26; so what I'm going to do is make the height 20--I'll keep the height--and I'm going to stretch it to 30, which is about 20% more--we're stretching things out 20% of 26; that's about 5; that's roughly 30, so I think we can get away with it.0871

Now, we're going to check the Resample Image again, but we're going to uncheck the Constrain Proportions; we're resampling it, but now I can go ahead and type in 30 inches, and you notice that it's going to go up in size, because I'm stretching it.0913

It's going to go up from 26 to 30; and I click OK, and it works, and look!--it actually looks better than it did--now it looks kind of squishy, even though that is natural, and this look makes a nice, wide-angle scene that works really well.0932

The quality level, I'm sure, is pretty good; we'll open it--there is where it was; there is where it is; it looks just as good.0947

So, there is one way of distorting (I'm going to go back to the original) an image by using image size.0958

That is resampling to distort; so you just check only the resample, and let the dimensions and resolution change to stretch your image.0967

Now, let's talk about canvas size.0977

I'm actually going to do it right here on this image.0981

Notice, I have some white space here, and I've kind of run out on the left; actually, we had better do it with an image so that you can see; the other one was white.0983

This is the image; let's say I would like to make a frame around this image--have a white border and not cut into the image.0995

What I can do is to go to Image, Resize, and I'll go, not to Image Size, because I'm going to leave the image the same; I'm going to Canvas Size.1004

Up comes this box; now, we know that the width is 15 and the height is 10, and the new size--you type in either inches, centimeters, whatever you want; you can change the extension color to foreground, background, white, black, gray, or another color.1012

I'm going to go ahead and extend it at white; and you can click Relative, and if I put 2 inches, it's going to go one inch on either side automatically; I'm just going to do it my way.1029

Right now, it's 15x10; let's set that back; again Option/Alt, Reset; this check box with arrows--right now, if I want it put one inch all the way around the image, if I type in 1 on the right, 1 on the left, that is two inches on the width.1045

I'll change it to 17; I'll change the height to 12; and the box is in the middle, which means it's going to allow expansion by the arrows, right and left, up and down, uniformly, and it's going to go up 2 and up 2, 15 to 10, 17 to 12.1066

Click OK and look; we have a white border around it, and it put it on the background.1084

All right, let's undo that and go back to Image, Resize, Canvas Size; let's say we want to only go and add something...let's just say to the left.1091

If I click to the right of the median, notice what happens: the arrows allow up and down, but they will only allow it to go left.1103

So, if I change the width now to 17, 2 inches, it's only going to allow it to go out this way; still white; I click OK, and see what happened: we have 2 inches over there.1112

Where would that apply?--let's go back to the one we were looking at now, and you see I'm getting pretty close to this edge; I have a little over here, if I want to balance it.1127

I'm going to go to Image, Resize, Canvas Size; I want to increase on the left side, so I'll click that right arrow so it can go left, and right now, it's 11; I'm going to change the width to 12 inches, click OK, and notice: it popped out to the right a full inch, which I think is a little too much, so I'm going to do Image, Resize, Canvas Size; and let's do 11.5; click OK; I have to make the box; and now, I have balanced the image out by adding canvas on the left side.1138

All right, let's go back to the descriptives; that is how you work with canvas size.1177

Now, we have covered (let's go with a new) resolution, pixels per inch, and how it relates to your image size.1186

If you change your document size alone, which is right here; you don't change the file size--you change the document size; if the document goes down, the resolution comes up; if the document goes, the resolution comes down, so the file size maintains the same.1198

Image size: increasing and decreasing; remember, you are resampling now to change, maintain proportions, or distort the image.1220

If you maintain the proportions, keep all of the check boxes checked, and now it will maintain proportions, but we could change this to 250; file size goes up; up we come, and it is now a bigger image than it was before, because we made it larger, but it looks the same.1233

If you want to distort the image, Image, Resize, Image Size; we're going to take the Constrain Proportions away, and let's say we make it 7 inches high; resample it; we're going up.1257

We click it, and you notice that it distorted things, because it stretched it upwards.1271

And then, canvas size is adding extra around, and you do that with Image, Resize, Canvas Size, and adjust the box to where you want to go.1277

If it's in the middle, it will go equally up and down or right and left; if you go in a corner, that means it only goes to the right and down; so, in other words, wherever you want it, you can set that to add wherever you need it on the canvas size.1288

There you have a lesson in resolution, image size, canvas size...and by the way, one final thing: sizing for print and Web.1305

We talked about the Web, which should be a 72 dpi.1314

When you open up an original file (let me bring one right out as a raw file and show you), there is the raw file; we'll open it; go to the Image, Resize, Image Size; and notice, it defaulted at 240 pixels per inch; that is the way all of the cameras do these days into Photoshop Elements.1322

The reason for the 240 is: if you're printing, not on your laser printer (you can do anything 300 dpi or up, or as far down as...until it degrades--whatever you want; the laser printers are fine, or inkjets), but if you're going out to a regular ink-on-plate lithographer, they can only print a maximum of 175 to 200 lines per inch.1346

What they ask is that you give them a file that is 1 and 1/2 to 2 times (typically 1 and 1/2 times) the resolution of the output print.1375

If you are printing at 175 dpi, one and a half times 175 is approximately 240, which is the reason that it defaults at 240--at 240, this image is ready, as it sits, to be printed on a lithographic printer.1388

So, preparing for print; you're going to go with 240 to 300 dpi (I can't draw very well--d-p-i), and for the Web, 72 dpi.1409

There you have all you need to know about resolution, image size, canvas size, and sizing for print and Web.1429