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No one takes pictures just to correct and edit them, of course. At some point you want to get your pictures out into the world, either as print or delivered as electronic images via e-mail or the web. To preserve the best possible image quality for your output though, you need to follow a fairly strict procedure when outputting your files, and that process begins with sizing your image for output. Most digital cameras these days capture a tremendous number of pixels, tens of millions of them in some cases. And very often these are far more pixels than you need. To get accurate results when sharpening and to speed the process of printing or saving and transmitting a file, it's best to size your image to the print side that you want using Photoshop.
We are going to size this image, with the idea of making an 8X10 inch print out of it. Now whether we were going to a bigger print size or an electronic file, we would still use the same tool for sizing our image. We are going to assume an 8 x 10 inch print. In Photoshop, all image sizing is done by going to the Image menu and choosing Image Size, which brings up Photoshop's Image Size dialog box, which is not just how you can resize your image. It's also a nice little calculator for determining how big an image might be able to go before you start seeing some visible degradation.
The Image Size dialog box is divided into two areas. There is Pixel Dimensions. These are how many pixels are in my image? This image is 4300 x 2900 pixels. Then there is Document Size. This is how big of a print will come out of this particular group of pixels. So right now, if I were to print this, it would be 18 x 12 inches because it has a resolution of 240 pixels per inch. In other words, if I take these 4,368 pixels and line them up so that there are 240 of them per inch, I will have a width of 18 inches.
Let's do a little digging around in the dialog box here. I am going to uncheck this Resample Image box. Resample means that Photoshop is allowed to throw out pixels or make up new pixels. When Resample Image is checked, all of these boxes are editable. I'm going to uncheck it. And you'll notice the first thing that happens is Width and Height are no longer editable, Width and Height in Pixel Dimensions, I mean. I cannot change the number of pixels in an image. All I can do is change the Print Size. So I'm fixed at having 4300 x 2900 pixels.
Let's say I change this to 10 inches. Photoshop automatically calculates that for the size of this image, 10 inches wide, my height will be 6.667 inches, to be precise, at a resolution of 436.8. So let's talk about this problem first. I said I wanted an 8 x 10. Well 8 x 10 is not a three to two aspect ratio, and that's what this image was shot at. So there is no way that I can get an 8X10 without cropping. So I am going to give up on the 8 x 10 idea, and say, well, I'll put this in something that's 10 inches wide.
And I'll just have some extra space about and below so it will be 10 x 6. We will talk about cropping it down later. That's an additional option. But I really composed of this image within the full frame, so I'd rather not crop it. However, when I sized my image down to 10 inches, my Resolution went way up. Because again, I've got 4,300 pixels, that can not change, so the only way to get an image that's 10 inches wide is to crush the pixels in closer together so that there are 436.8 of them for every inch. Do I care what the Resolution is? I certainly care what the Resolution is if the Resolution is too low.
Do I care about having too much? Yes. You don't necessarily have to, but it's a good idea to build resolution that's appropriate for your printer, for a couple reasons. It'll make your files smaller. It will make your printing go quicker because you won't have as much data to transmit to the printer, and the printer won't have to sit there and chug through a whole bunch of extra pixels that it doesn't need. And it will make your sharpening efforts possibly more accurate. On a desktop inkjet photo printer, that is a printer that has six or more ink cartridges in it, you really never need a resolution higher than 240 pixels per inch.
You can go up to 300, that's okay, but 240 is kind of about as good as you need. If you were to take this out to another printing technology, maybe to send it to an offset printing place, they might want 300. So let's just go ahead at 300, and then we will have an option for printing on an inkjet or some other way. So if I change Resolution now to 300, uh oh. Now my Width changed. It went back up to 14. Again, this is because I cannot lose any pixels in this image, because these aren't editable right now.
And Photoshop indicates this by showing that all three of these fields are linked together. I cannot change one without the other. You can think of pixels as a quantity of brown sugar. You can pour a certain amount of brown sugar into one size cup and fill it up to the top. You could then take that brown sugar and stick it in a smaller cup and possibly crunch it down to fit in there. You're not changing the size of the brown sugar grains, but you are compressing them closer together. You're increasing the resolution, the density. That's what we are doing with these pixels. What I would like to do is be able to have 10 inches wide at 300.
But again, I can't do that right now because these three things are linked together. To unlink them and get what I want, I have to check the Resample Image box. So now these are editable. I've got a Width 10 inches. If you notice, I currently have 4300 pixels for 72 mega-pixels worth of data. If I crunch this down to 300, my pixel count just dropped a lot. It dropped down to 3000 and my overall dimension is changed. So now I have a 10 x 6 at 300 pixels per inch.
This is now resized properly for print. Let's look though at trying to get an actual 8 x 10 out of this. There is no way I can get 8 x 10 out of this using the Image Size dialog box, because if I put 8 in here, 10 will change because Width and Height are linked together because I have Constrain Proportions checked. So I have to actually go into a crop now to get this down to 8 x 10. I am going to cancel out of here. So no changes have been made. And I am going to grab Photoshop's Crop tool.
I can specify, though, the dimensions that I would like to crop to. I would like 10 inches wide and 8 inches high. I don't have to fill in the Resolution field if I don't want to, but I'll go ahead and put it at 300. That'll just save me from having to type that in later in Camera Raw. And I am going to hit the Caps Lock key to change from the Crop tool cursor just to crosshairs, because I find that easier. And I am going to start dragging a crop. Now this is a constrained crop. I can only drag out something that is the correct aspect ratio for 8 x 10.
So Photoshop CS5 has a couple of new features in its Crop tool. It's got this Crop Guide Overlay, which lets me display these different grids and things. I don't actually want those right now; those are distracting. And as in previous versions of Photoshop, I have this shield that comes over here that hides more of my image. I can change the color of it how pink it is and just trying to give me a preview of what the crop will look like. So my goal here now is to find a good crop. And I'll say, right off the bat, that I'm not going to think any of these are good crops, because I really framed this in the camera the way that I wanted.
But really the big part of his image is this cloud thing right here. I could take this crop. It looks weird to me because I've got all these stuff up here. So I am going to try squeezing that down to there to bring a little more focus just to this big, brightly-colored thing here. So the image is losing a lot, but I am going to go ahead and take that crop. Photoshop is going to think about it. And when it's done, I'll go to the Image Size dialog box and double check that it has put my crop where I want it.
Image > Image Size, and now I have a 10 x 8 at 300. So if I had to fit this into a particular frame size, or output to a particular size to go on a specific size box in a web page or something like that, I could do that very easily with the Crop tool. So this is the Image Size dialog box. You will be using it probably on every image that you output. If you're going out to the web, you will possibly have specific pixel dimensions in mind. You might need to output an image that's 640 x 480.
I can just type 640 in here. And then I see that okay I've got the wrong aspect ratio for 640 x 480, because that would be a four to three aspect ratio. Anyway, I could work through this again and get those to the sizes that I want. How large should you go for print? A lot of people think that, well, if my printer wants 300 dots per inch then I have to always have 300 dots per inch. And that's not true, because as an image goes larger, you view it from farther away. If you're printing out 11 x 17 or 13 x 19 inch image you are probably going to frame that and hang it on the wall.
You're inherently going to stand at a greater distance from that then you would a 4 x 6, which you are going to hold in your hand and look at. So as image size goes up, the resolution that you need can go down. Now we are going to talk about enlarging and reduction in the next lesson.
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