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In this exercise, I am going to show you how to downsample an image for print, which may sound crazy. After all this time spent with me telling you that you want to capture the image at the highest resolution afforded by your digital camera or scanner and keep those pixels in as good shape as possible, why would you downsample the image and throw a bunch of pixels away? Well, there's a few reasons to do it. One is that you're emailing the image to somebody else and you want them to see it on their screen. Well this is too big to email for one thing. Typically, you can't email things that are bigger than 10 megabytes and this is a very huge file, I think it's like 150 or something.
Also, if you were to somehow successfully get it to them, then they are going to look at that image on their screen probably not in Photoshop, they probably don't own it and even if they did they don't really know how to use it let's say. So they're opening the image in some other program and most programs are terrible. What they'll do is they'll try to shrink the image so that you can see the entire image on screen at once and they are terrible about downsampling on the fly like that, and as a result you get these horrible jagged transitions. I mean they really, really look rotten. And the person who is looking at your image will think it's your fault, so you want to make sure and make that image as there I say idiot proof as possible.
So it's already scaled for their screens. Secondly, you might want to send this image off to your printer and you don't want to waste their time and you don't want them to have to downsample the image either. Basically you're just trying to make sure the image is scaled for the occasion. So here's how it works. First of all, presumably you are working in a layered image and you go ahead and save your changes to a PSD file using the Save or Save As command. Leave that file alone. You are not going to save over that one. Then you go up to layer menu and you choose the Flatten Image command. It's dimmed for me because this is already a flat image.
And I've given you a keyboard shortcut by the way, if you load the dekeKeys of Ctrl+Shift+Alt+F or Command+Shift+Option +F on the Mac, and then you downsample the image for the occasion. So in our case, we want to print the image let's say. I go up to the Image menu and I choose the Image Size command, press Ctrl+Alt+I, Command+Option+I on the Mac. Notice I already have scaled this image to 12 inches wide, a little more than 8 inches tall and Resolution of 993 pixels/inch. That's fine and we did that with Resample Image turned off.
Now this time what we want to do is we want to keep this image 12 inches wide. It should still be a little more than 8 inches tall. That's fine. But we want to knock the Resolution value down and we want to downsample the image in the process. So go ahead and turn Resample Image On this time. Make sure that Constrain Proportions is turned on, and we don't need to Scale Styles because this is a flat image, but it's a good habit to make sure Scale Styles is turned on because when in doubt if you do have layer effects you want to scale them as well. Next, we are going to leave the Interpolation set to Bicubic, because there's no reason to smooth away noise inside this image.
And I was telling you Bicubic Sharper is great if you're going to the web, if you're generating a very small screen image, and this would be great by the way also if you're emailing the image to somebody else. But in our case, we're printing and the sharpness that's produced by Bicubic Sharper is going to disappear on print, we are not going to see it. So anyway, leave it Bicubic and reduce the Resolution value. We're are not concerned about Width and Height, because they are already where they need to be. Reduce the Resolution value to 360 pixels/inch, and that's going to be the maximum number of pixels you need to print this image.
That would be great for Inkjet printing, for high-end Inkjet printing by the way and it's more than enough for a commercial reproduction and so on. So then click OK. Now you are going to downsample the image. Notice that the first value is less than the second value, so it was 273.4 megabytes, now it's going to drop down at 35.9 megabytes, much smaller and so you are going to lose pixels in the process. But they are going to be blended away and actually the pixels that are left are going to be in better shape. That's the great thing about downsampling.
Whereas with up sampling the new pixels are in worse shape than the old pixels with downsampling the new pixels are in better shape than the old pixels. So in other words, the detail has coalesced essentially. I'll click OK in order to accept that modification and we will see the size of the image reduced here on screen. All right. Let's go ahead and switch to our lead sheep here once again by pressing and holding the H key and clicking for the Birds Eye function and then I'm going to release when I get these guys in the right location on screen here about here is good.
Now let's compare that just briefly to what happens if we had up sampled that small image to match. So I'll switch to the small image and this is the one that's called, Shepherd and small flock.tif inside that same 05_image_size folder. And I'm going to go up to the Image menu, choose Image Size and this time around I leave Resample Image turned on. I'll change the Width value to 12 inches, I'll enlarge the Resolution to 360 pixels/inch. I'm not going to worry about interpolation, Bicubic is just fine and notice now that we're definitely up sampling, was 1.9 megabytes, now it will be 35.9 megabytes.
The same size we saw just a moment ago. The pixels take up the exact same amount of room. They are just based on less information, so they are not going to be in as good as shape. So I'll click OK in order to rewrite the pixels, then I'll press and hold the H key and drag the Birds eye around these guys like so, and I'll scroll him over to about this location here and now we should have a good match. This is the downsample version of the image as you can see incredibly crystal clear lines and information and detail inside this image.
Let's Shift+Tab away the right side panels so we can see more of the image on screen at a time. This is the up-sampled version of the image. We've got blurry detail. It's gummy. It's murky, we can't see the lines nearly as well. It's actually a mess. So contrary to what you might think, enlarging an image in Photoshop produces typically bad results whereas reducing the size of an image inside of Photoshop produces typically great results. So upsampling usually bad, downsampling usually good.
Now then would I save over my original image? Absolutely not, I would of course go over to the File menu and choose the Save As command so as to preserve the original pixels in a different file along with layers and everything else I'd want. So you Ctrl+Shift+S or Command+Shift+S on the Mac and then you'd save the image under a different file name. You can still use the TIF file format because this is a flat file. And there you have it, the benefits of downsampling for the occasion inside Photoshop.
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