10 Replies Latest reply on Mar 1, 2015 8:32 AM by MW Design

    How to mix 72ppi with 300ppi?

    sarahpeller Level 1

      Hi there,

       

      I am working on a photo collage that will end up being printed as a large banner. All of the photos that I'm using are 300 ppi and I believe will work just fine, but one of the images is 72 ppi. However, when I look up the image size in Photoshop it says that the pixel dimensions are 5540 x 3694 and the document size is 76.944 inches x 51.306 inches. Does that mean that it's low resolution, but could be printed huge? Resolution stuff is so confusing for me!

       

      Thanks for your help!!

        • 1. Re: How to mix 72ppi with 300ppi?
          rob day Adobe Community Professional & MVP

          5540 x 3694 and the document size is 76.944 inches x 51.306 inches

           

           

          It can also be 18.467" x 12.313" at 300ppi (5540/300=18.467) without changing the number of pixels. You can do it in Photoshop by unchecking Resample in Image Size, or by scaling the image down in InDesign, which produces the same result. When you scale down the Links panel will show you Effective Resolution, which is the output resolution.

          • 2. Re: How to mix 72ppi with 300ppi?
            sarahpeller Level 1

            So, let me get this straight...

             

            It is now 5540 pixels at 72 ppi.

            And if I were to resize this in PS, I'd uncheck "resample" and change the ppi to 300. I thought that you were never supposed to up the ppi because it just 'says' it's now 300 ppi, but nothing can make it more than 72 ppi?

             

            But if I wanted it to print at 300ppi, which could be printed as large as 18 inches, then I could resample in PS as you mentioned and then place into Indesign OR just place in Indesign as is...

             

            So if effective ppi is now 703, then it could be printed as large as 7.88 inches?

             

            Am I getting this right?

            Thanks so much for your help!

            • 3. Re: How to mix 72ppi with 300ppi?
              Per Berntsen Adobe Community Professional

              What matters here, is the pixel dimensions of your image - 5540 x 3694. When you change the ppi from 72 to 300 in Ps with Resample unchecked, it's still 5540 x 3694 pixels.

              And with simple math you can figure out how big it's going to print, by dividing the number of pixels with 300.

              5540:300=18.46, 3694:300=12.3. It will print 18,46 x 12.3 inches. (Or, change the units in the dialog to inches to let Ps do the math for you)

               

              If that's too big, change the unit to inches in the Image Size dialog, check Resample, and enter the values you want. You will now be downsampling, which is OK, as opposed to upsampling, which is bad for quality.

              • 4. Re: How to mix 72ppi with 300ppi?
                rob day Adobe Community Professional & MVP

                I thought that you were never supposed to up the ppi because it just 'says' it's now 300 ppi, but nothing can make it more than 72 ppi?

                 

                Your confusing resampling (adding or subtracting pixels—upsampling or downsampling) with resizing (changing the size of the pixels). If you check Resample and changed the resolution from 72 to 300 ppi the pixel dimensions of your image would be increased to 23083 x 15392—you would add a lot of pixels without changing the output dimensions of the image. That kind of resolution increase is ineffective because the added pixels are interpolated.

                 

                So if effective ppi is now 703, then it could be printed as large as 7.88 inches?

                Right the image can have an output width dimension of 7.88 at 703 ppi, or 18.467" at 300ppi, or 24.622" at 225ppi

                • 5. Re: How to mix 72ppi with 300ppi?
                  MW Design Level 4

                  Have you checked with whomever is printing this job as to what resolution they want? Many/most large format printers like to receive a PDF that has 150 dpi resolution at 100% size. Whomever is printing your job should have recommendations for your particular job.

                   

                  As mentioned, DPI means little to nothing, it's all about the pixel dimensions once placed and ID will express the effect of the sizing of the placed image as Effective PPI. But it's all about the pixels.

                   

                  How large in inches does this image expect to be when placed? Once placed, what does ID report the effective PPI? An image of the pixel dimensions you indicate can likely comprise 1/4 to 1/3 of the long edge of the design.

                   

                  Mike

                  • 6. Re: How to mix 72ppi with 300ppi?
                    Test Screen Name Most Valuable Participant

                    I think one of the sources of confusion is that in Photoshop, Image Size does two ENTIRELY DIFFERENT JOBS according to one simple selection.

                     

                    * With resampling: changes the image. Removes quality or adds junk. Beware and understand consequences!

                    * Without resampling: changes information ABOUT the image. This is important but does not reduce quality in itself.

                     

                    Let's focus on what happens without resampling and what ppi really means. It is just pixels per inch. Think about what that means. If you have 600 pixels in 2 inches, then you have 300 pixels in 1 inch, and that's 300 ppi. That's what it means and all it means.

                     

                    If you have an image 600 pixels wide and you put it on a page at 2 inches wide it will be 300 pixels per inch. If you doubled the size to 4 inches wide, it would be 150 ppi. Take it to 10 inches wide and you have 60 ppi. And so on. Some of these numbers will be a problem, and this is where you have to understand your printing technology or work with the printer (person). If the printer says "you need 200 ppi" then for this image you can't use it over 3 inches wide.

                     

                    So what does the ppi value in the image mean? It is just a hint as to the size you'd expect. Some apps will use that size and others will completely ignore it; some might use it as a default but let you drag to resize.

                    • 7. Re: How to mix 72ppi with 300ppi?
                      sarahpeller Level 1

                      Thank you for all of those great and helpful responses! So, I'm wondering about another way of going about this. I made a postcard for a client. She wants to take this postcard and blow it up into a 6 foot wide banner. I'm wondering if I can just change the page size of the postcard to 6 feet wide and then inspect my photos from there.

                       

                      Here's a screenshot. I selected the lower right photo and checked out the info panel. It says effective ppi is 136. Does that mean that this photo will look pixellated at this size? Is there a certain standard effective ppi that I don't want to go under? I will check with the printer on Monday...

                       

                      Is there any way to achieve a higher effective ppi by resizing some of these images in photoshop? Or do I just have to give up on these photos and find higher res ones?

                       

                      Also, should I go into photoshop and make sure that all of these images have the same ppi before placing them into this banner image?

                       

                      Screen shot 2015-02-28 at 2.02.47 PM.png

                       

                      Thanks!!

                      ~ Sarah

                      • 8. Re: How to mix 72ppi with 300ppi?
                        Peter Spier Most Valuable Participant (Moderator)

                        I think you'll find this discussion useful: Distance-Resolution Formula

                        • 9. Re: How to mix 72ppi with 300ppi?
                          rob day Adobe Community Professional & MVP

                          It says effective ppi is 136. Does that mean that this photo will look pixellated at this size?

                          You could also get a small proof—copy part of the image into a letter sized page leaving it at 100% of its final print size and you’ll see the effect of 136ppi in actual output.

                          • 10. Re: How to mix 72ppi with 300ppi?
                            MW Design Level 4

                            Most large format printers I have sent work to like a target resolution of 150 dpi at 100% scale. I would say if your printer has that as the target dpi and the images one will focus on the most meet or exceed that target it will be fine. It shouldn't look pixilated per se as much as slightly fuzzy.