72 dpi- saved as 96 dpi

[eilona74866288]

Hi, when im save filae in 72 dpi- after i export the image i go to the file properties but the dpi set as 96.

For now I converting it to 72 dpi in a website. but can anyone know why is that happening and how can i fix it?

tnx!

[Test Screen Name]

Export removes the resolution so you see the defsult. Different apps and systems have different defaults.

For online use this is all fine. For print use don‘t Export.

[Laurence-Baker]

PPI or DPI does not matter to a screen. Only pixel dimensions matter.

So, exporting at 72 PPI is fine. Exporting at 96 PPI is also fine. It's just a bit of pointless metadata to a screen

When you go to print, PPI does matter. Because you are saying represent 300 pixels on one linear inch of paper.

It's very confusing, but it's not be helped by companies like Adobe, not adding the word Print in front of the word 'Resolution' in some dialogue boxes.

[eilona74866288]

tnx, but i have a customer that need all the files to be 72 dpi (it's a requiment for the website or something...) he don't really care about the quality.

any other options? maybe to export as 60 dpi?

[Derek Cross]

As already mentioned, the image resolution is irrelevant in this context, (and by the way the measurement terminology is PPI – Pixels per inch, not DPI) as the pixels will be matched to the screen resolution.

[Laurence-Baker]

As Derek and I have pointed out. The PPI of an image does not matter to a screen.

But, if you want to output at 72 PPI, to keep your client happy - use:

File > Export > Export as

File > Export > Quick Export

File > Export > Save for Web

They will always output at 72 PPI.

Best Workflow IMO:

If you need a certain pixel dimension for the web. And, the image does not meet those dimensions, use the Crop tool to crop to the Ratio you need.

If you need 1024 x 768 let's say, just enter those dimensions on the Ratio boxes, and make sure Delete Cropped Pixels is Not ticked.

Then just use of the export methods above, and enter 1024 x 768 as the size, and leave the Interpolation on Automatic.

It helps to think in terms of the PPI of a screen, not the image. The higher the PPI of a screen goes up, the smaller an image of a given size will be.

That's why with high pixel density screens like Retina you may have to serve a single image with three different pixel dimensions. x1, x2, x3. because of the Retina screens will make certain images very small. It's called the Device Pixel Ratio. So, if a device browser reports it has a Device Pixel Ratio of x2 then the server will serve it an x2 image.

If we were to go along with the falsehood that the PPI of an image matters to a screen. You are effectively saying I want an image of 72 PPI to change the resolution of the screen to make sure the image has 72 pixels displayed on one inch of screen. That doesn't happen.

The only way to get an image change size on a screen is to change the resolution of the screen.

I realise it's confusing, but it's vital to understand this concept as we go forward with high pixel density screens.

[Test Screen Name]

Absolutely do not mess with the image. Send the files you've made, they are NOT 96 ppi and NOT 72 ppi either.

[Test Screen Name]

No, Laurence-Baker, NONE of those will output at 72 ppi. Rather, they will output with no ppi at all, which is the root of this problem (I agree, of course, for web use, it is best not to look at or care about ppi). Of the Photoshop means of saving, only Save As will preserve the ppi metadata. If the customer ABSOLUTELY DEMANDS a ppi that is set to 72, Save As is the only way.

[Laurence-Baker]

YOU ARE WRONG

Take an image of 300 PPI for example. Export the image using Export As. Open the exported image using let's say with Preview on a Mac. Go Tools/Show inspector - you will the see the PPI (or DPI as Apple wrong call it) will be 72.

If you actually carry this experiment out and you come up with any other PPI than 72. Or no PPI is shown at all, which is what you are suggesting) - I will apologise.

And as I said previously PPI doesn't matter to a screen at all, it's just a bit of Metadata embedded in the file.

[Test Screen Name]

A lot of software does not tell you that no ppi is available, and instead show their default, which might happen to be 72. Never blank. I believe Finder is exactly such software. So is Photoshop.

Eilona, may I ask you, if you're still with us, what app or system is showing the 96 ppi.

[D Fosse]

No, Laurence, you are wrong.

The 72 figure appears when the file is reopened into another application. Most applications need to assign something if there is no ppi value present. So most of them assign a default value of 72, but a few will assign 96  (or some other value).

You can all stop shouting now. This is how it is, let's move on.

[Laurence-Baker]

I find this hard to believe. Why would a photo viewing program like preview need to assign any value to a file like PPI? Sure it just reads the metadata that's there.

Show me some documentary evidence.

[D Fosse]

Any application that might be asked to print the file will need a ppi value. Any ppi value will do.

No need to go further than Windows Explorer, which assigns 96 by default (yes, they should know better than calling it dpi):

And here's the same file opened in Photoshop:

But why do you need evidence? It makes perfect sense. Ppi isn't needed, so out it goes.

[Lumigraphics]

:sigh:

Adobe writes a resolution tag into the TIFF XMP namespace. If that tag is deleted (Save for Web IF you don't choose All or All except camera data) then Adobe will default to 72 ppi. I haven't checked to see if Preview or other viewers add a resolution tag or just have a default for a missing tag.

You can look at tags in Bridge or Photoshop File Info and see this. A script that removes the tag or entire TIFF namespace will give you that change.

Having said all that, ppi is irrelevant on screen. Total pixel dimensions are what matters.