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Resizing & Cropping Images / Understanding Resampling
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Subtitles of the Movie (Adobe Photoshop CS5 / Resizing & Cropping Images / Understanding Resampling)
Thankfully, this is where the rabbit hole ends. We've made it to the end of the journey here. We really only have one more issue to discuss and that is the issue of this thing called Resampling, so once again I'll do my best to explain all of this in straightforward terms for you. So I'm obviously right where I left off from the previous video. I'm still inside the Image Size dialog box and what I would like you to do, for the time being anyway, is turn off the Resample Image option down at the bottom. And what's interesting to note is, as soon as I turn off the Resample Image option down at the bottom the Pixel area at the top grays out. I can't change the Pixel Dimensions anymore inside my image. So, in other words, all that I have available now is the Width, the Height and the Resolution. So let me explain resizing images without Resampling and you know, if you're jotting some notes you might want to write across at the top of your page How to Resize Images Without Resampling, or something like that. First of all, when we have Resampling turned Off we are not changing the pixel count inside our image, we're only changing either the Resolution or the physical size, the print size of our document. So, in other words, when we have Resample Image turned Off and we resize our image we are not impacting the quality of our image and that's very important. So we're not going to be degrading the quality of the image or anything like that. Now what's interesting to note here as well is if I change my Resolution, my PPI value don't forget - maybe I'll take this guy and I'll drop him down to 100 - what that does is that either increases or decreases the physical size, the document size. So I dropped my Resolution down to 100 and that cranked up the document size up to 15 inches square. If I take my Resolution and I bring him up to 600, that then reduces the physical size of the document. What the heck is up with that? Well, I'll try to explain it in the next video in more detail. Essentially, it's like a teeter-totter, or a seesaw. If I drop the Resolution, then the physical size increases. If I take the physical size, for example and I drop him down, maybe down to 3 inches, then that increases the Resolution. So when one's up the other's down and vice versa. And all of this is related to resizing your images without Resampling. Have a gander up at the top. The pixel size of the image has not changed, even though I've been messing around down in this area here, it's still 1500 pixels squareright? I'm going to use my little Reset trick here holding down Alt or Option and then clicking on Reset to start over again here. Now what I want to do is I want to resize my image with Resampling and this is actually where it gets a little bit more hairy. I'm going to make sure that Resample Image is now turned On down at the bottom and what Resampling will do is it will change the number of pixels inside your image to match the document size and it will impact the quality of your image, in fact, it's practically the mirror opposite to resizing without Resampling. So everything I said about resizing without Resampling is now opposite in this world with Resample Image turned On. So, in other words, if I come in here now to my Resolution and I change my Resolution, maybe I'll drop it down to 100 pixels, the document size now remains the same. It's still 5 by 5 but I've now impacted the Pixel Dimension. I now have shaved off 1000 pixels from my Width and Height. Or, if I come into the Resolution area and I crank this up to 600 pixels, well, it's still a 5 by 5 inch image but now my Pixel Dimension is 3000 pixels in Width and Height. Now here's my question for you. When I first opened up this image it was 1500 pixels squareright? And it had a Resolution of 300 PPI. I doubled the Resolution to 600 which doubles the pixel countright? So here's my question for you. Where did the extra 1500 pixels come from, how is that possible? Well, that's what Resampling, or another phrase for Resampling is Interpolation - say that 5 times fast - that's where all that comes in and this is really what this option is all about. So, in other words, what I've done here is I've told Photoshop that I want to double my Resolution, which doubles the pixel size and Photoshop goes, OK, I have to make up 1500 pixels out of nothing. How do you want me to do that? And that's what this drop-down menu, all the way down at the bottom of the dialog box, is all about. These items in this drop-down menu are what are referred to as Resampling, or Interpolation Methods. Now, I don't want to go completely off the deep end on you here because it's probably tough enough to wrap the noodle around, but there's a bunch of them in here. We have Nearest Neighbor and Bilinear and a few Bicubics there. Essentially, these are different mathematical algorithms that are going to be used to recalculate pixels inside your image, whether it's a photograph or a cartoon robot, or whatever you have. So, one particular Resampling method might be better for one particular image and then you might have another image you open up and you might have to wind up using another algorithm, another Resampling methodright? So, essentially, what we're doing when Resampling is turned On, just as a recap here, is we are impacting our image's quality. Sizing our image down, making it smaller, is usually not a big deal. It's when you try and make your image bigger. If you take a 5 by 7 photo and try and convert it into an 8 by 10, well Photoshop has to make that extra image up out of nothing, right? So I can choose how Photoshop makes up those extra pixels and there really isn't any silver bullet here. Again, it all depends on the image that you have, so what I would suggest is open up your image and make sure Resampling is turned On and throw in your values into this dialog box and perhaps start with Bicubic, best for smooth gradients, see how that looks and then possibly revert your file and then come back in and try one of the other options. For example, if you're making your image bigger you can try Bicubic Smoother, best for enlargements. Oftentimes with the type of work that I do I find myself using Nearest Neighbor because I have a lot of hard edged images like cartoon robots. So, that's kind of a brief introduction, anyway, on the issue of Resampling. Now I want to dig a little bit further into this world of Resampling and Resizing your images, both with Resampling and without Resampling and I want to try and give you some tactile, real world examples.
Tutorial Information
| Course: | Adobe Photoshop CS5 |
| Author: | Geoff Blake |
| SKU: | 34150 |
| ISBN: | 1-936334-46-1 |
| Release Date: | 2010-08-06 |
| Duration: | 7.5 hrs / 95 lessons |
| Work Files: |
Yes |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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