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In this movie, I'll explain what to do if you have to upsample an image. Now normally, I try to avoid upsampling as much as possible because you're always better off capturing a high resolution image in the first place. But there are times where upsampling is just unavoidable. For example, here I am looking at a detail from the Moab skyline.jpg file. That's the high resolution version of the image. And let's say I have a client who wants to print this image 30 inches wide. So I go up to the Image menu, choose the Image Size command. Of course, I turn off the Resample Image check box and then I dial in a Width value of 30 inches and I note that the Resolution value is 233.333 repeating Pixels/Inch.
That's not necessarily ideal, but that's better than 220 Pixels/Inch, which is a nice rule of thumb minimum, so that will do just fine. So now I just click OK, don't harm a single pixel on the image and it's ready to go. But what do I do if I'm working from a low resolution version of the image like this one here? So this is the image that I downsampled in an earlier movie. If I go up to the Image menu and choose the Image Size command and take that Width value up to 30 inches, that drops the Resolution value down to 58 and a third Pixels/Inch, which is awfully low.
Now it's not necessarily too low however, it's not nearly enough pixels, if you anticipate that people are going to be looking at the image from a distance of just a few inches. But if this image were about for a billboard or some other distant environment where a person is going to be standing several feet or even yards away, then a low resolution value like this is not necessarily a problem because the pixels will resolve from a distance. However, let's say you want to put this on a poster people are going to see it up close, then you would regrettably turn on the Resample Image check box, go ahead and leave it set to Bicubic Automatic, which is going to grab that Bicubic Smoother setting.
And I'll increase the Resolution value to 233.333 just because I know that's what I'm looking for, and then I would click OK. Well I've got to have done that in advance. So I'll show you what that looks like. We end up getting this effect here. Now we do have smoother transitions, we don't have to jagged pixel effect anymore. So these are the actual pixels in the original image that I've not upsampled, and this is the upsampled image subject to Bicubic Smoother. Now one of the big problems is though we can see magnified halos around these details, which is a function of the fact that when I downsampled this image I left the interpolation set to Bicubic Automatic, which grabbed Bicubic Sharper and generated the halos.
So sharpening isn't always a positive effect over the lifetime of the image. Now there's another rule of thumb that suggests that you want to divide your upsampling into pieces. So you'll apply just a little bit of upsampling at a time. And that's where this image comes into play. It's called Upsampled Moab x10.jpg. Now what I did in this case was I went up to the Image menu and chose the Image Size command. And I turned on the Resample Image check box of course. Left the Interpolation set to Bicubic Automatic and I switched to Percent, and the Percent value that I dialed in was 114.87%.
Now where in the world did I get this value? Well the percentage difference between the low-res image and the high-res version of the image is 400%. You may recall that our original image had a resolution of 400 Pixels/Inch and I took it down to 100 Pixels/Inch. So that's where that comes in. So to figure this out, you whip out a scientific calculator, which you get on an iPhone at any rate, by viewing the calculator horizontally, and then I took the number 4, which is 400%, and found the 10th power of that number, and it turns out to be 1.14.87, you multiply that times 100 to get the percent.
It's so easy, right? Anyway, then I clicked OK and applied that exact same modification 10 times in a row. Now if you want to do that, if you want to try that out, you may want to load an action that I've created in advance. You go to the Window menu and choose the Actions command, and then in the Action panel, you go to the flyout menu and you choose the Load Actions command, and you'll find an Action file in the 03 Image Size folder called Multipass upsample. Go ahead and load it up. Then you just want to click on Upsample 400% right there and click on the Play button in order to play that back.
In any event, we end up getting this effect here. Well, that's a pretty long-winded way to tell you. I don't think it works worth beans, I will go ahead and switch back to the single pass of upsampling. So here I just upsampled the image to 400% in one fell swoop, and here is the version of the image in which I upsampled in 10 passes. There's almost no difference whatsoever. We have some smoother halos but that's about it. And in fact, if that's kind of the route you want to go, if you want to achieve a plastic, sort of modeled effect, then what I would recommend you try out is the Bilinear setting.
So if you set the interpolation to Bilinear, you're going to see a little bit of jagged edge around the outline, it's just a titch; however, you're also going to see a lot less in a way of haloing. And then finally, here's my real true advice. If you find yourself upsampling on a regular basis and it's a kind of thing that just part of your job, then there's a program that does this better than Photoshop. It's available from a group called onOne Software, so you go to ononesoftware.com and you search for a product called Perfect Resize, and this is the effect that it produces.
Notice that we have extremely plastic details. We don't end up with much of any haloing and it ends up comparing the best to the actual high resolution file. So this is a true high-res version of the image, and this is a version that I upsampled in Perfect Resize. So again, if you're going to upsample in Photoshop try to take it easy, don't go as far as I've gone in these examples, they're just for demonstration. Stick with one pass of upsampling. I think it works just as well and it's lot easier to pull off.
And then finally, if it's a regular part of your work, look into Perfect Resize.
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