Though they are similar, PPI refers to the pixels per inch on your computer screen, while DPI refers to the ink dots per inch applied by a printing press. Again, the easiest way to think about it is:. NOTE: Resolution applies to raster images, which are comprised of pixels, but not vector images, which use mathematical calculations to produce images. Learn more about the difference between raster and vector images.
What resolution should photos be for printing? In many cases, the best resolution for printing is PPI. At pixels per inch which roughly translates to DPI, or dots per inch, on a printing press , an image will appear sharp and crisp.
These are considered to be high resolution, or high-res, images. What about the best resolution for pictures online? Web images are commonly created in 72 or 96 PPI, which are considered to be low resolutions.
Low resolution, or low-res, images will appear pixelated and blurred after printing — even though they might look perfect on your computer screen. That means there would only be pixels spread out over four inches. To make that stretch, each of those pixels would need to be rather large, resulting in a blurry, pixelated image. Compared to the 72 PPI version, the four-inch span would be represented by 1, pixels instead of pixels — or more pixels.
That means the pixels can be smaller, resulting in higher definition and clear, sharp image. For example, if you want to print high-quality business flyers on an offset or digital printing press, your flyers should be PPI. Those are examples; every printing company has its own resolution requirements. The best pixel size for print can vary between printing companies, printing formats and printing presses. The higher the resolution of your camera, the larger you can print images and still get a clear output.
How many pixels are in PPI depends on the document dimensions. You can multiply both 8 and 10 by to get the full pixel dimensions of the finished image.
Another name for 7. For another example, we might want to figure out how many pixels are in a 5 x 7 image. Again, we need to know the PPI. So a 5 x 7 image at PPI would be 1,px by 2,px. Now, you can figure out the total megapixels by multiplying width times height:. In this case, you can print a high-quality 5 x 7 photo by snapping a picture with a 3. Take the guesswork out of file preparation with free layout templates for brochures, postcards, business cards, greeting cards, stickers and more!
How do you find the resolution of an image? How can you tell if an image is high resolution? Brush Tool Tips. Load New Brushes. Using Custom Shapes. Color Correction with Curves. Change Image Size to View on Screen. Image Size for Printing. Change Image Resolution. New Document Size Preset. Image Optimization for Web. Install PlugIn Filters in Photoshop. Repeat Filter. History Palette. Fast Scanning. Save Workspace in Adobe Photoshop. For now, to see how resolution affects the print size of the image, uncheck Resample to turn it off:.
As soon as you turn Resample off, you'll notice that the measurement type for the Width and Height values changes. Instead of viewing the width and height in pixels as I was a moment ago, I'm now seeing them in inches. And instead of telling me that my image is pixels wide and pixels tall, I'm now being told that it's In fact, if you click on the measurement type box for either the Width or the Height, you'll notice that Pixels is now grayed out and unavailable.
That's because, with Resample turned off, we're not able to change the physical number of pixels in the image. All we can do is change the size that the image will print , and print size is usually measured in inches or centimeters depending on where you are in the world :.
Resolution controls the print size of an image by setting the number of pixels that will be squeezed into every inch of paper, both vertically and horizontally. That's why the resolution value is measured in pixels per inch , or " ppi ". Since the image has a limited number of pixels, the more we cram those pixels together on the paper, the smaller the image will print.
This means that when I go to print the image, of its pixels from the width, and pixels from the height, will be squeezed into every square inch of paper. Now pixels may not sound like much.
But remember, it's from both the width and the height. In other words, it's times , for a total of 90, pixels per square inch:. To figure out the print size of the image, all we need to do is divide its current width and height, in pixels, by the resolution value.
If we look again at the Dimensions section at the top, we see that the width of my image is still pixels:. If we divide by the current resolution value of , we get In other words, the width of my image, when printed, will be If we divide by the current resolution of , we get Which means that the height of the image, when printed, will be 10 inches, just like it shows in the Height field:. If we change the resolution value, the number of pixels in the image doesn't change, but the print size does.
But the width and height both increase. Since I'll only be squeezing half as many pixels per inch onto the paper, both horizontally and vertically, the width and height have both doubled:.
And since all we're changing is the print size, then changing the width or height will change the resolution. In fact, when the Resample option that we looked at earlier is turned off, all three values Width, Height and Resolution are linked together. Changing one automatically changes the others. If I lower my Width value down to 10 inches, then to keep the aspect ratio of the image the same, Photoshop automatically changes the Height value to 6.
And to fit the entire image into the new, smaller print size, the pixels will need to be packed in tighter, so the Resolution value has increased to A common misconception with image resolution is that it somehow affects the image's file size. Many people believe that, before you email a photo or upload it to the web, you need to lower its resolution to make the file size smaller.
This is simply not true. Since changing the resolution does not change the number of pixels in the image, it has no effect at all on the file size. If you look next to the words "Image Size" at the top of the dialog box, you'll see a number, usually shown in megabytes M. In my case, it's This number represents the size of the image in your computer's memory.
When you open an image in Photoshop, the image is copied from your hard drive, uncompressed from whatever file format it was saved in, and then placed into memory RAM so you can work on it more quickly. The number shown in the Image Size dialog box is the actual, uncompressed size of the image:. Proving that image resolution has no effect on the file size is easy. Just keep an eye on the size while you change the resolution.
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