Difference between DPI and Pixel Size

[Zephyr Windwalk]

Hi, I'd like to know the difference between DPI and pixel size, and how it can affect the quality of the image I upload on social media (Facebook, twitter, etc). As far as I know, DPI is for printing. Pixel size is for computer image itself. If I upload a Facebook cover page which is (820 x 461px. DPI is 72) but the problem is the picture is somehow pixelated. Now one suggested that it should be 300 dpi to ensure that its clear and high resolution. Would anyone, disagree because it should stay 72 DPI and the pixel size should be the one to adjust.

My question is:

Is there any difference between adjusting the DPI or pixel size? They said its different.

[gener7]

If resample is checked, then increasing the ppi from 72 to 300 would blow the pixel dimensions up 4X which would blur the picture because it's making up detail. Not a good idea.

2048 pixels lengthwise is optimal Facebook banner size. Try creating (not enlarging) your banner at that size.

Let me know if that improves things.

But, correct, ppi is Print metadata for paper, monitors display pixels.

[Zephyr Windwalk]

Thank you for your reply.
Well, the images where Hi-res and it's in smart object. I tried to suggests recreating the banner but the team still push the 300 dpi. They seem confused about definition of dpi.

If resample is not checked, there's no difference between 72 and 300 dpi right?

[Test Screen Name]

No difference to Facebook, which reads and recompresses all images, sometimes quite harshly with poor results. Don’t try to optimise the image compression, in fact my instincts are that best results will come from PNG.

I suspect this this is much discussed with a lot of advice on the web, some good, some bad, and some nonsense.

[Zephyr Windwalk]

Ok. Thank you for your answer.

[gener7 · Accepted solution]

Correct. Only the print (document) size changes, not the pixel dimensions.

72

300

[Zephyr Windwalk]

Ok. I'll try to show this to them. I hope this will convince them somehow.
Again, thank you for your answer

[D Fosse]

https://forums.adobe.com/people/Zephyr+Windwalk  wrote

I hope this will convince them somehow.

Make it simple. Get them to think long and hard about what pixels per inch means, literally. Pick apart the three words. It's a simple equation, fully defined in those three words.

[Test Screen Name]

Equally 300 will do no harm and you can show them it does no good either.

[JJMack]

An image DPI setting is a Prints Pixel size.  An Images DPI setting is meaningless when it come to displays. Displays can not change the size of the Pixels they display that have a single pixel density.  Printers can print pixels any size up to their max print resolution.   For example inkjet printers use many smaller droplets of ink to paint in your images larger pixels.

The quality of your image determined by the quality of the pixels you have for your image.  You camera gives you the best pixels you will have for an image.  These may or may not be high quality pixels.   For High quality pixels you need to use a high quality camera with a good lens, use good exposure settings. there needs to good light and the camera needs to be steady.  The image quality you will get from your camera will vary from image to image.

When ever you resample an image from you camera you will loose some image quality for the number of pixels has been changed using some interpolation method.   If you reduce the number of pixels in the image you had to discard some details your camera captured for there are fewer pixels to store details in.   If you increase the number or pixels you have to create details your camera did not capture.   The image quality depends on how much details need to be discarded or created. So you should always resample the image your camera captured.  Never loose that image file your camera created.

[Zephyr Windwalk]

Thank you so much for the info.