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In this movie, I'll show you how to downsample an image with the intention of emailing it or posting it to a photo sharing or social media site, something along the lines of Google Plus or Facebook, Twitter, Flickr, there's a bunch of them out there. And mostly, the idea is to reduce the size of the file on disk to 5 megabytes or less is usually a good goal. And you also don't want the image to be so big that it can't be viewed on the largest monitor out there. Now, currently, I'm seeing this image, which is a panorama of Moab, Utah from the Fotolia image library, and I'm looking at this image at the 17% view size. It happens to be 7,000 pixels wide, and it's about 20 megapixels in all. Plus, it takes up 12.8 megabytes on disk as a compressed JPEG file. So we definitely want to trim things down, by first going up to the Image menu and choosing the Duplicate command, just so we don't ruin the original. And I should have mentioned this before, if your image contains layers, you can just turn on this checkbox, Duplicate Merged Layers Only, and that'll give you a flat file.
In my case, I already have a flat file, however. So I'm just going to call this guy Downsampled Moab, like so. And then I'll click OK. And I've now got a copy of the image. The next step, of course, is to go up to the Image menu and choose the Image Size command. And notice the dimensions here, 7000 pixels by 2800. And we've also got an uncompressed file size of 56 and a half megabytes in RAM. This is a ginormous image. Now, when I'm downsampling images just for whatever web purpose I might have and I'm not sure exactly what size I want the final file to be. Because, sometimes, you know exactly the pixel dimensions you want, but generally you don't, and so, I'll usually switch here from Inches to Percent. And just figure that I'll take the file size down to some percentage, maybe start at 50% and see what you end up with.
And that's going to give me an image size of 14 megabytes in RAM, which is pretty darn big. Now, you can figure that when you save the JPEG file, it's not going to be much more than a third of that. But, it's going to vary depending on a detail inside the file and you also want to pay attention to the dimensions. Notice that the final is still 3500 pixels wide and nobody out there owns a screen that's that big. In fact, very few people own screens that are more than 2000 pixels wide.
So we need to take the file size down farther. I'm going to try 33% and see what we get. Now, that's going to give me 2300 hundred pixels wide, a little bit of change there. And we're coming up on a 1000 pixels tall, which seems about as big as I want this to be. Now, I want to show you something, you may not be able to see this in the video, but when I drag the image it looks a little bit jagged, and when I release it gets all smooth. Check this out, when you're downsampling images things behave differently than when you're upsampling, here inside the Preview.
I'm going to go ahead and zoom in by clicking this Plus button to 300%. And notice we're getting big pixels, because after all, we're zooming in beyond 100%. But if I click and hold, the image looks better. So in other words, it looked better before I downsampled it than it looks after. So, Photoshop is going to show you the original version of the image. Perhaps a little bit jagged, however, in my case, it's not jagged in the least when I click and hold. It gets jagged only after I release and that's because 33% here, times three ends up giving us a 100%.
So in other words, this is our 100% view of the original image when I click and hold. All right, so, that pretty much takes care of it. We've gotten the image size and RAM down to 6 megabytes, which is definitely in the clear. Again, the JPEG file probably going to be about a third that size. So now, what you want to do is go ahead and click OK in order to downsample that image. And you can see, it's much smaller on screen. But if I press Ctrl+1 or Cmd+1 on a Mac in order to zoom in 100%, it's still plenty gargantuan on this screen. All right, now, what you want to do is save off the file as a JPEG image. And you do that by going up to the File menu, and choosing either the Save or Save As command, doesn't matter, because this file has not been saved yet. I'll just go ahead and choose Save or you can press Ctrl+S or Cmd+S on the Mac, and you can see, I've already provided you with a file called Downsampled Moab.jpeg. I'm going to go ahead and replace it right now, and I'll click on the Save button, and click Yes to replace the image.
And then, you'll see the JPEG Options dialog box. What I recommend you do is always, always, always save at the maximum quality setting. Don't take it down to, I believe 8 is the default and that's just going to mess up the image. That's going to apply too much compression and it's just not worth it, so many people make that mistake with their web images, they overcompress and it just destroys the experience in my opinion. Go ahead and crank it all the way up at a quality setting of 12, which is the highest inside this dialog box, you end up getting JPEG compression that you cannot even see, you're not going to notice a difference.
And you get this little preview that tells you that your file's going to be 1.9 megabytes. Now, that's an approximation. It may be a little off, but it's going to be somewhere around there, and then you also want to turn on baseline optimize, because that's going to apply lossless compression as well. It may not make a difference in terms of the file size, but sometimes, it does and it's worth it. And then you want to go ahead and click OK in order to save off that file. And now, it's ready to email. You can typically email images 10 megabytes or smaller.
And you could certainly post this on any of the sites out there. So that's how you downsample an image for email, as well as any variety of online photo sharing here inside Photoshop.
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