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I created an invitation card of double the A4 size with 72 dpi in photoshop. I intend to share it via phone. However when seen in actual size, it gets blurred.

I tried same with 300dpi also.

What should be properties of image so that it should not get blurred irrespective of the screen size, when seen at the original size of the image.

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what was the device? –  Ctrl Alt Design Apr 4 at 11:13
    
The properties of the image should match the pixel dimensions that it will be shown as. If it will be shown on a device that is 640 x 1120 pixels, then the image should be exactly that: 640px x 1120px. –  DA01 Apr 4 at 19:31

3 Answers 3

up vote 2 down vote accepted

The DPI is not relevant. If your screen is 500x300 pixels, then the optimal size for full screen on the device is 500x300 pixels.

If you give an image that is any other size it MUST be stretched up or squeezed down. Both result in quality degradation an blurring. It must be, no question. So the only thing to consider is "do I do it myself or allow the OS to do it?" Usually, the OS or software uses a "fast" method to scale instead of the "best" method.

DPI is dots(pixels) per inch, but the inches change per device. The only constant is pixels. DPI is merely a hint or tag in image files. The data is either vectors (math) or pixels (fixed dot unit).

If your next question is "Does that mean, for the best quality, I need a uniquely sized wallpaper with pixel dimension tailored to each target mobile device?" then the basic answer is "YES"

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horatio's answer is good. I'd mark that the answer.

To offer some more information:

What density should be used to create mobile wallpaper?

The answer is "it doesn't matter". When you are printing images, you have complete control over the density. You get to decide how much information per inch of printing will be there by changing the DPI settings in your image creation software.

But with screen graphics, you don't have control over the density. The device does.

As such, any DPI setting you have in your image is simply ignored when presented on screen. All that matters is the overall pixel dimensions of your image.

A quick experiment to explain this:

  • Open photoshop and create a 300 x 300px image at 72dpi.
  • Save this as a JPG
  • Now go to IMAGE SIZE and change the dpi to 300 (But do not resample).
  • save this as a different JPG

Now open up both JPGs in your browser and you will notice that they appear exactly the same size: 300px x 300px.

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Stick to using 72 dpi screen. 300 dpi for print.

http://en.wikipedia.org/wiki/Dots_per_inch

How was you sharing the image? could it be the sharing processes that degraded the image quality?

Or possibly the way you saved the image?

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1  
Please use the answer-fields for well argued answers only. The questions you pose, are better suited for the comment fields. –  Benteh Apr 4 at 12:35
    
72 dpi is a habit, but really has nothing to do with screen images at all. Whether it's 72 dpi or 720 dpi, it will look the same in a web browser/on a phone. –  DA01 Apr 4 at 19:29

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