ĭirectly to the question, based on the above: See also my answer on What exactly is a "Pixel"?. Later, we looked at the screen and measured that it's, in fact, 100dpi Īnd, there is not only one screen the image could be shown on - they could be different in size, so it's not even possible to know a real dpi value when creating an image file.ok, then we need about 200dpi or so." and saved the "200dpi" in the file But we had an idea how it should look like, "roughly this size.We did not know the dpi the images, shown on a screen, will have, because we did not know the screen.Normally we do not even know what the end user will use as display, so we can guess only anyway, Then, we used a screen that was showing it as 5 inches wide - we can know that because we know what the actual screen is. ![]() The file was promising - by saying 200dpi - it will "2.5 inches wide when shown". And nobody cares! Because it's just not relevant. ![]() So, as you see, the promise was just plain wrong. When we assigned the image dots to the screen, we did not even care about that, because we just displayed it, and measured the actual, physical dpi of the screen representation of the image. So, the dpi value in the image is telling us that our image will be 2.5 inches wide when displayed - as a promise, not as a fact. The dpi value is about how many color dots are visible per inch of screen width or height. Now, if we look at our file, it may well say the image is 200dpi! ![]() That is, our image has 100dpi on the screen.īut we did not even look at the dpi value in our image file! Then, we have 100 rectangles per inch, showing 100 of our dots per inch. If we display an image in this natural way on a screen, we can measure it's size.įor example, our image is 500 dots wide, we put these into colored rectangles on the screen, and see it is 5 inches wide. Note that both, what I call "dots" and rectangles here, are called "pixels" - but looking closely they are something different. Now, when you show an image on a screen, you will normally just put the dot colors of the image into the raster of colored rectangles that your screen can display. But the do not have size in any physical sense. In short, your image consists of dots of colour, which are next to each other. With that, you may just see the answer yourself.: I will go into details what the "dpi" actually means, by examples Whether you choose to use 72, 96, 200, or 145.8 ppi doesn't matter, but all the images should be set the same. You will want all your images to be set at the same ppi to avoid resizing and scaling of aspects should you move pieces between images. When working with multiple images it's important to remain consistent. It's the (pixel) width and (pixel) height of an image which are important. It doesn't make any difference what ppi setting you use for web images. A more appropriate acronym would have been xPPI or PPIx because mobile screens, like all displays, use pixels and not ink. If you see DPI in relation to mobile screen resolutions, they are speaking about effective PPI and not really referencing Dots Per Inch. This is not the traditional form of the acronym and the manufacturer has simply muddied the waters a great deal. Since no display on Earth uses ink, DPI is an incorrect term to use for anything related to display screens.īe aware some mobile manufactures chose to use the term DPIx or xDPI which is sometimes shortened to simply DPI. DPI refers to the amount of ink dots/spots the press will place within an inch. DPI has no bearing on images destined for screen. They are both 100px by 100px images still.ĭPI (Dots Per Inch) settings are only applicable when printing an image. are they any different in a web browser? Nope. Make one image 72ppi and the other 300ppi. Create two images in Photoshop both 100 pixels by 100 pixels. In fact, it was never accurate for Windows systems, because Windows uses a default of 96ppi for pixel density.ĭon't believe me? Try it for yourself. 72ppi hasn't been accurate for over 40 years. In reality, a monitor using a pixel density of 72ppi hasn't been seen since the early to mid 1980s. The pixel density of retina displays is higher however, they still display image at whatever the screen states is the width and height of an image not based on any PPI setting. This is why images for retina displays are saved at 2x size, rather than an increased ppi setting. ![]() In fact, many web images such as png, gif, jpg may not even store a ppi setting in their internal data and rely on width and height settings.Ī 100 pixel x 100 pixel image displays as that on the web regardless of any PPI/DPI setting. Images on the web, retina displays or otherwise, are displayed by their pixel dimensions (width and height) not any PPI/DPI setting. PPI (Pixels Per Inch) settings are not used in web images.
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