Photoshop’ Default Resolution of 72 Resolution Gives Less Flexibility?

[KostFan2]

• Question: Adobe’s default resolution setting, 72, seems to give users less flexibility for resizing.
  Why does Adobe choose 72 instead of 240 or 300 as the default resolution?
• Setting: Edit/Preferences/Units & Ruler/Screen Resolution: 72
• Issue: When customer Resamples/Resizes an image (Open image/Image/Image size).  If it says 72 (default) and the customer wants to downscale the image further, they are limited to a maximum reducing it by only 71 degrees to “1”.
  If 240 was the default then they could reduce it by a maximum of 241 degrees to “1”’
• History:
  a) I assume the original resolution setting was based on the relatively high cost of storage and the fact that 72 results in a smaller file on the hard drive.
  b) However, in this “Tik Tok” era, the adobe customer’s friends are viewing the images on a device (phone) with a small screen where they pinch with their fingers to zoom in to see the images.  If the image has been resized to 72 then the viewer has limited zooming capability.  In contrast, if the resolution default is 300, then viewers can zoom significantly so they can see the details in the face of the person in the photo.
• Is my understanding incorrect?
  I know the customer can change the default and create presets as well.  However, I am trying to understand why Adobe does not change the default setting based on today’s customer use of products (zooming on cell phones). I assume most readers of this post have changed their default and presets to either 240 or 300.  Is that correct?

[davescm · Accepted solution]

You need to separate out ppi which is a metadata value used in printing, by the printer driver, to decide how many pixels will fit per inch of printed media from pixels. For on screen use ppi is irrelevant and just a number stored alongside the image data.

For example : A 3000 pixel by 2000 pixel image at 72ppi is exactly the same as a 3000 pixel by 2000 pixel image at 600 ppi. Both will contain the same image information. However when printed on paper, the 72ppi version will measure 41.6 inches by 27.7 inches wheras the 600 ppi version will measure 5 inches by 3.3 inches. Both though will contain exactly the same image information - no more, no less. On screen they will measure whatever the screen pixel density sets the image to and both will zoom to the same degree as image ppi is not used for displaying on screen. Hence why Export strips out the ppi data altogether.

Note : The value in Preferences > Units & Rulers > Screen resolution is used to show rulers at actual size and ensure that View > Print Size works correctly. It should be set to the pixel density of your actual screen (mine is 109ppi) yours will be different.

Dave

[KostFan2]

Dave:

This community is fantastic.  Thank you for your very detailed and yet clear answer.  However, sometimes it is like reading a foreign language. 

You say: “The value in Preferences > Units & Rulers > Screen resolution is used to show rulers at actual size and ensure that View > Print Size works correctly. It should be set to the pixel density of your actual screen (mine is 109ppi) yours will be different.” 
Please confirm you have changed your default from 72 to 109. 

Please also confirm that this default setting has nothing to do with the number after “Resolution” when you select image/image size.

[davescm]

Yes those two values are completely separate.

The screen resolution is the number of pixels in each inch of your monitor. It's value should be set based on the specification of your particular monitor.

The image resolution sets how the print driver will put the pixels onto the paper. Literally ppi means how many pixels will be placed in each inch of paper.

Dave

[KostFan2]

Thank you!

[KostFan2]

@davescm 

Dave:

I want to thank you. I wish I had discovered this Forum years ago.  My understanding of Lightroom and Photoshop would be lightyears ahead of where it is today.  I am quickly learning that you Community Experts are more useful than Adobe phone support. Why? Because you actually use the products on a daily basis instead of “Trouble shooting” them.  As a result, your knowledge is both broader and deeper that 100% of Level I support and perhaps 85% of Level II support.

For example, 2 different Level II Suport staff told me that the screen resolution setting at Preferences > Units & Rulers > Screen resolution is used to set the presets for the Film/Video tab.  While that information is correct, it is not complete. Thank you for sharing your knowledge with me.