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  • Ppi

    Hi. Could someone please tell me how to change the pixels per inch value from 72 to 300? Without resizing the image. Thanks.
    David

  • #2
    Can you provide some context?

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    • #3
      Hello Antelope,
      I don't know the exact terms of the English interface but, in French, you have to switch to Edit mode via the Geometry / Resize menu. There you will find a "Resolution" slider with which you can change the number of pixels per inch.
      I hope my English is understandable.

      Comment


      • #4
        Thank you so much for your reply Framon. I have searched and searched for this slider but cannot find it anywhere!

        There is a facility in Resize for setting the print resolution, but unles you are changing the size, merely altering the resolution and clicking apply doesn't seem to change anything.

        Regor, if you go to manage mode and look at the file info, you will see the 'Pixels per inch' number there. It's usually 72, 96 or 300. The latter is for printing, the former are for displaying on a screen. That said, I cannot imagine what this number does as if an image is, say, 1000 pixels wide, it will print at ((1000/300)x2.54) centimeters wide, and will display on screen at whatever resolution the screen is. So what can this PPI number do? I do know that when I sent some images to a pro printer, he insisted that the PPI be set to 254, which is how he operated. So it means something. If anyone can elucidate, I'd be grateful.


        Nonetheless, in the interest of having all possible problems covered, I want to set the screen versions of my images to 72 (or should it be 96?) and my print versions to 300.

        Comment


        • #5
          Here a screenshot from the French version :

          Click image for larger version

Name:	Redimensionnement.jpg
Views:	51
Size:	51.7 KB
ID:	57648

          If it is for a screen display, 96 dots per inch is sufficient in most cases.

          You can easily find articles on the Internet explaining the difference between "resolution" and "definition".
          Attached Files

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          • #6
            Ah yes, but changing it only works if you also change the size of the image. You cannot open a 72PPI image, only change that number to 300PPI and click 'done' and expect the PPI to change. If you now look at the file in Manage, the file info will still display 72PPI.

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            • #7
              Maybe another solution: File / Export and change the dimensions.
              Or Tools / Batch / Resize...(translation from French).
              Last edited by Framon; 10-13-2021, 05:52 AM.

              Comment


              • #8
                Antelope


                There is a plethora of information about ppi and dpi available on Google so no point repeating it here.

                Basically both are used as a measure of density.
                dpi refers a print density when printing to physical media, for instance paper.
                If an image is for example 6000 x 3000px and it is printed at a dpi of 300, then it's physical size would be 20" x 10"
                If a 6000 x 3000px image is printed at dpi of 600, then its physical size would be 10" x 5"

                ppi is used to refer to screen and digital elements.
                For instance a scan of a 6" x 4" image at 600 ppi would give a higher resolution image than if the scan was done at 300 ppi.

                My 1920 x 1080px Acer monitors have a specified ppi of 99 so regardless of the ppi/dpi the 6000 x 3000px image displays at 20% zoom as 12.12" x 6.06"

                In common usage ppi and dpi are considered to be the same, so 300 ppi is considered to be the same as 300 dpi.

                Now to answer your original question.

                Within ACDSee, there is no way to change the dpi/ppi of the original image. You can however export a copy of the image with a different dpi/ppi.
                In the export dialog, in the Output Size section, specify the ppi you want, but leave the "Resize Image" unticked.

                If you want to change the dpi/ppi of the original image, you would have to use a 3rd party like ExifTool. Note however that for RAW formats that contain an embedded low resolution preview image the Exif metadata may have multiple x and y resolution values.

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                • #9
                  Thank you for this additional information. So I wasn't completely wrong...

                  Comment


                  • #10
                    So export allows you to but the save options don't.

                    OK, many thanks everyone.

                    Comment


                    • #11
                      This thread has got me thinking. I don't print my own images; I send them to Mpix to print for me. If I'm viewing the images at 72dpi, shouldn't I increase the dpi of the image to 600 dpi before I upload it to Mpix's server? If yes, what is the best way to do this?

                      Comment


                      • #12
                        Originally posted by Mamiya2Nikon View Post
                        This thread has got me thinking. I don't print my own images; I send them to Mpix to print for me. If I'm viewing the images at 72dpi, shouldn't I increase the dpi of the image to 600 dpi before I upload it to Mpix's server? If yes, what is the best way to do this?
                        The ex camera images I have from a number of different DLSR and SLT cameras generally have ppi's of 300 to 350 as shown in the Image Atttributes section of the ACDSee Ultimate Manage>Properties Pane, File Tab. This value comes from the Exif metadata in the image.

                        Ex camera images on the other hand from both iPhone and Samsung Galaxy smart phones show the ppi as 72.

                        The screen shot below shows the image attributes from a Samsung Galaxy smart phone image.

                        Click image for larger version  Name:	Image attributes.jpg Views:	0 Size:	54.3 KB ID:	57668


                        If you look at the Image dimensions in the screen shot below, you see that if printed at 72 ppi (or more correctly dpi since we are talking about physical prints) it would be a very large print, 56" x 42". I'd be pretty sure the prints you are getting back are not that size, so your prints are not being done at the Exif dpi value, but probably at what ever dpi results from fitting the pixel size image (4032 x 3024 px in this case) to the ordered print size.

                        So my answer is that if you are happy with the prints you are getting, there is probably no need to change ("if it ain't broke, don't fix it").
                        If you do want to change the dpi/ppi without changing the size of the image then see my post #8 above. https://forum.acdsee.com/forum/main-...7658#post57658

                        Edit: To take this a little further. The aspect ratio of the above Samsung Galaxy image is 6:4.5. So If I wanted to print it on precut 6" x 4" photo paper, I would have to crop it. And when I select the crop tool in Ultimate's Edit Mode, and constrain the cropping proportion to the preset 6 x 4, I can then set the resolution to 300 (ppi), or what ever I prefer.
                        Last edited by Greyfox; 10-13-2021, 03:41 PM.

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                        • #13
                          There are a lot of articles on the Internet explaining what resolution to use for photo prints depending on their size.
                          Keep in mind that for large formats, it is useful to use a resolution of about 20 Mp when shooting.
                          In addition, it is also useful to know from what distance you will look at the printed photo. It is rare that we look at a poster at a short distance.
                          There is a simplified formula that has no standard value for calculating the dimensions of a printed photo based on the number of pixels of which it is composed with a resolution of 300 dpi :
                          Good quality: divide the number of pixels in the width and height of the image by 30 to get a measurement in centimeters.
                          High quality: divide the number of pixels of the width and height of the image by 60 to obtain a measurement in centimeters.
                          Example for an image of 3000 x 4000 px:
                          Good quality: 3000/30 = 100 cm. 4000/30 = 133 cm (39 "x52").
                          High quality: 3000/60 = 50 cm. 4000/60 = 67 cm (19.5 "x26").
                          As I said, this is an oversimplified formula that only gives an approximate value. It will never replace real tests.

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