12 Replies Latest reply on Nov 11, 2017 3:04 PM by Per Berntsen

    Resizing to 1200px wide, 120dpi in Lightroom

    sandytdavis

      i need to resize an image to 1200px wide, 120dpi.  How do I do that in Lightroom?  Thank you.

       

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        • 1. Re: Resizing to 1200px wide, 120dpi in Lightroom
          dj_paige Level 9

          There is no such thing as a dpi for digital images. It only refers to printed images, and it is a printer setting.

           

          Lightroom can resize your photo in the Export dialog box. Under Image Sizing, check "Resize to Fit", then set the dropdown menu to Long Edge (or Short Edge, depending on which you want to be 1200 pixels), and type in 1200 and set that dropdown to pixels.

           

          How to export Lightroom Classic CC files to disk or CD

          • 2. Re: Resizing to 1200px wide, 120dpi in Lightroom
            Per Berntsen Adobe Community Professional

            sandytdavis wrote:

            i need to resize an image to 1200px wide, 120dpi.  How do I do that in Lightroom?

            To set the ppi (that's what it's called) to 120, enter 120 in the Resolution box in the Export dialog.

            I assume you are going to print the image, and setting ppi to 120 will result in the 1200 pixels printing 10 inches. (1200:120)

             

            dj_paige  wrote:

            There is no such thing as a dpi for digital images.

            I wouldn't go as far as that.

            Although ppi is not a property of a digital image, it is optional metatda, and enables printer drivers to calculate print size.

            Consequently, the Export dialog allows you to enter ppi, so that prints come out the right size.

            • 3. Re: Resizing to 1200px wide, 120dpi in Lightroom
              JimHess Adobe Community Professional & MVP

              I have never had a printer that was affected that way by the PPI setting in a file. The PPI setting is really only there as a reference as far as I know.

              • 4. Re: Resizing to 1200px wide, 120dpi in Lightroom
                Per Berntsen Adobe Community Professional

                Do you send the full resolution image to the printer, and let the printer driver scale the image down to fit the paper?

                In that case, I guess the ppi doesn't matter so much - with a small print there will more than enough pixels to print the image with reasonably good quality.

                 

                I always export the image to the exact size that I want (I print from Photoshop, not Lightroom), and in that case having the correct ppi is crucial, otherwise the image might print with reduced quality or wrong size, depending on whether you have used physical dimensions or pixel dimensions in the Export dialog.

                Inkjet printers also have sweet spots at certain ppi values - Epson printers supposedly produce the highest quality prints when the ppi can be divided by 180. I use 360 for prints up to around 16 x 20", and 180 for larger sizes on my Epson 9880.

                • 5. Re: Resizing to 1200px wide, 120dpi in Lightroom
                  wobertc Adobe Community Professional

                  I agree-  "ppi" is only a 'reference'.

                   

                  But- there are people in this world that do not understand.

                  My case- I submitted an image 6016x4016 pixels for a newspaper advertisement,

                  the 'junior' type-setter contacted me to say my image was not "detailed" enough for a newspaper advertisement.

                  On investigation I had exported if full-size at 72ppi, so  "72ppi" was seen by the type-setter as "low quality".

                  Nothing would convince him/her that it had all the "quality" it needed. Only a re-submission of the file with an embedded 300ppi reference would be accepted.

                   

                  And I have books on Photoshop and 'Digital photography' written 10-15 years ago that will perpetuate the "ppi/dpi" confusion if a reader is to believe what was written.

                  • 6. Re: Resizing to 1200px wide, 120dpi in Lightroom
                    dj_paige Level 9

                    https://forums.adobe.com/people/Per+Berntsen  wrote

                    dj_paige   wrote:

                    There is no such thing as a dpi for digital images.

                    I wouldn't go as far as that.

                    Although ppi is not a property of a digital image, it is optional metatda, and enables printer drivers to calculate print size.

                    Consequently, the Export dialog allows you to enter ppi, so that prints come out the right size.

                    DPI is not a property of digital images. PPI can be a property of digital images.

                     

                    In the case where you set the width to 1200 pixels, PPI is ignored.

                    • 7. Re: Resizing to 1200px wide, 120dpi in Lightroom
                      sandytdavis Level 1

                      Interesting comment.  I️ was asked to submit a digital image with those specifications.

                      • 8. Re: Resizing to 1200px wide, 120dpi in Lightroom
                        Per Berntsen Adobe Community Professional

                        dj_paige wrote:

                        PPI can be a property of digital images.

                        Ppi is optional metadata, and not really a property of a digital image.

                        Pixel dimensions, on the other hand, are a (required) property of a digital image.

                         

                        In the case where you set the width to 1200 pixels, PPI is ignored.

                        No, the ppi is not ignored.

                        The OP has confirmed that she was asked to submit a 1200 pixel image at 120 ppi, which leads me to think that the image will be printed.

                        When the printer driver reads this image, it will divide the pixel dimensions (1200) by the ppi (120), and print the image at 10 inches.

                        Sandy could also have set the dimensions (long or short side) to 10 inches instead of 1200 px in the Export dialog, and the result would have been the same. But physical dimensions are not a property of digital images (only pixel dimensions are), so the printer driver would carry out the same calculation as when the size was set to pixels.

                        So the ability to set physical dimension in the Export dialog is only for convenience. If the dimensions were set to 5 inches in the Export dialog, the image would be resampled to 600 pixels.

                         

                        Let's see what happens if the ppi is set to 240 instead of 120 when exporting.

                        If pixel dimensions (1200) are used, the image will print at 5 inches (1200:240).

                        If physical dimensions (10 inches) are used, the image will be resampled to 2400 pixels (10 x 240).

                        So when printing, the ppi is not ignored, and it's not "just a reference". It's a very important number.

                        For screen viewing, the ppi is of course irrelevant - the image will display according to its pixel dimensions.

                        • 9. Re: Resizing to 1200px wide, 120dpi in Lightroom
                          dj_paige Level 9

                          The OP has confirmed that she was asked to submit a 1200 pixel image at 120 ppi,

                           

                          No the original poster asked for 1200 pixel at 120 dpi. DPI is not the same as PPI. These are different, one does not imply the other. DPI is a printer setting (or scanner setting), it is not an image setting.

                           

                          Much of this thread (and much of what you have written, Per) confuses DPI and PPI, by assuming they are the same.

                           

                          If you export with the longest edge (or shortest edge) at 1200 pixels, then setting 120 ppi or 300 ppi or 732 ppi gives you the exact same image, you get an image with 1200 pixels on the longest edge (or shortest edge). Not a single pixel changes.

                          • 10. Re: Resizing to 1200px wide, 120dpi in Lightroom
                            Per Berntsen Adobe Community Professional

                            I am well aware of the difference between dpi and ppi.

                            When people ask about dpi on this forum, they mean ppi in 99% of the cases, and there is no way to have Lightroom export an image with a certain dpi. Whoever asked the OP for this image clearly meant ppi and not dpi, the latter doesn't make any sense.

                             

                            Of course no pixels will change when you export an image with size set to pixels and different ppi numbers.

                            But the printed size will change.

                            • 11. Re: Resizing to 1200px wide, 120dpi in Lightroom
                              Jao vdL Adobe Community Professional & MVP

                              >But the printed size will change.

                               

                              I don't think there is any layout app that really respects the ppi setting. Everything that is used to layout images allows you to stretch and squeeze as much as you want. Only app that I have seen that respects it is Apple's preview which of course nobody in their right mind uses for printing.

                              • 12. Re: Resizing to 1200px wide, 120dpi in Lightroom
                                Per Berntsen Adobe Community Professional

                                Although you have the option to resize an image in a layout app or printer driver, it's not good for image quality, but there are probably a lot of people who do this, and are happy with the results.

                                Personally, I always export and apply output sharpening at the exact printed size, which results in better print quality than if you resize the image after exporting and output sharpening. With this workflow, it's crucial to use the correct ppi.

                                 

                                That's why I think it's wrong to tell posters that the ppi number is not important, or that it's merely a reference.

                                I realize that not everyone who posts here need professional quality, but I think they want their prints to look as good as possible, so we should give them the best possible advice on how to achieve it.