Join Deke McClelland for an in-depth discussion in this video Calculating the actual print size, part of Photoshop CS3 Sharpening Images.
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So now that we know about the reliable zoom ratios and we know what the resolution of our screen is, what do we do with that information? Well, I am going to show you how to use that information in order to gauge the sharpness of an image and proper sharpening settings to apply, the best Amount and Radius values for example. And we will see that inside of this image, Stunning 12x8.JPG found inside the 01HowitWorks folder. You may recall that, this is that wonderful image from photographer Alexander Alexis that already looks sharp enough; we just want to make sure that it weathers the storm for commercial output and that it looks nice and sharp on the page.
So what I am going to do first, I am going to investigate what my print resolution is. I am going to go up to the Image menu and I am going to choose the Image Size Command or I can press Ctrl+Alt+I or Command+ Option+I on the Mac and we can see that if set this image to print at 12" wide x 8" tall and I have enough pixels in order for the resolution to be 267 pixels per inch, which is one of the standard print resolutions. There are no magic numbers where print resolutions are concerned, but 267 is based on twice 133 LPI Halftone Screen, that's where this comes from.
It is not really necessary that you know that. It is just that 267 and 300 and 360 are some common print resolutions out there, but you can print at anything from about 220 PPI up and get some very sharp imagery out of most printers. So meanwhile let's say I am working on a 17 inch MacBook Pro. It is fairly hilarious that I am doing that given that I am running Windows Vista, but still it is a minor problem. I am working on a 17" MacBook Pro and it has a resolution of a 117 pixels/inch. So what we would do is, we will whip on our calculators right, you must have one sitting around some place, and you would divide 267, so take the number 267, and divide it by 117 and you will get the number 2.28. That is going to be our multiplier.
So 2.28. Just scribble that down, if you have already figured out what the resolutions of your screen is, it may be something entirely different. Why then, divide 267 by it. so maybe your screen resolution is 102 pixels/inch, you divide 167 by 102, do the math, write down the multiplier number on a sheet of paper. Then go ahead and cancel out. We do not want to change the resolution of this image, this is what we want to do instead. Go up to the Image menu and choose Duplicate, and I want you to call this Actual print size because this guy is really going to represent the printed size of the image.
Go ahead and click on the OK button, then I want you to go up to the Image Size command, so this is a separate version of the image, go up to the Image Size command here and I want you to make sure that Resample Image is turned on. Make sure that Bicubic is selected (best for smooth gradients), make sure that Constraint Proportions is turned on. Scale Styles doesn't matter, but you might as well turn on all of your check boxes. Then I want you to change the Resolution value, in my case to 117. Now you might change it to something else, like I said if your screen resolution is 102, change it to that.
So go ahead and change the Resolution value to the resolution of your monitor and then click OK. And then I want you to zoom the image into the 100% zoom ratio. So press Ctrl + plus, or Command + plus on the Mac, until you see a 100% up here inside of the title bar. This is the size at which your image will actually print. Now let us go back to the other image, the Stunning 12x8.JPG file. Go ahead and select it, and I want you to go to the View menu and I want you to choose this command right there, Print Size, and it will zoom the image out to what Photoshop thinks is the size at which the image is really going to print. But notice how these two images here, they fairly differ from each other.
Your actual print size, which is the real deal my friends, is different from Photoshop's version because Photoshop, in this case, is wrong. Why is Photoshop wrong? Because Photoshop is assuming the resolution of your screen is 72 pixels/inch. Now you could set Photoshop straight, by going to the Units and Rulers section of the Preferences dialog box and changing the Screen Resolution value. I could change that to 117 pixels/inch and then Photoshop would get the size right. The problem is that's not going to be a good zoom ratio for you.
So it's going to be of no use where sharpening is concerned. The upshot is where gauging sharpening is concerned, this Print Size command here is of no use to you whatsoever. Having interpolated the image, we now have an accurate picture of the image. I want you to go back to it, the actual print size version, and we're going to use this version of the image to gauge the best Amount and Radius values, and we're going to use those values to sharpen the big version of the image, the Stunning 12x8.jpg file, and we're going to do that in the very next exercise.
- Understanding the effects of sharpening
- In-depth examinations of Unsharp Mask, Smart Sharpen, Emboss, and High Pass
- Smoothing an image with the Surface Blur, Despeckle, and Reduce Noise features
- Working with smart objects and smart filters
- Creating edge masks and non-edge masks
- Sharpening for digital-image capture using Camera Raw
- Gauging and exploiting luminance frequency
- Exploring creative applications of sharpening
- Sharpening a multilayer composition
- Sharpening eyes, hair, and out-of-focus backgrounds
- Reducing noise in a high-frequency image
- Determining ideal settings for commercial and inkjet output
- Sharpening very large-format images
- Sharpening an image for the web or screen output