14 Replies Latest reply: Mar 16, 2014 8:53 AM by digital paradise RSS

    Lightroom export page DPI settings for screen viewing

    digital paradise

      We are having a debate on another site about this. If you watch any Photoshop videos or look this up on the internet you will find that DPI has nothing to do with screen resolution, only print. If you select LR's web page it does not even offer a DPI setting.

       

      The debate is that someone read that Jeff Schewe who was involved in the develpment suggested to set DPI from 72-150 because it effected the sharpening algorithms. This apparently is by design and unique to Lightroom only.

       

      I did several tests at 1 DPI and 1000 DPI and I have trouble seeing any difference. Also I find it is difficiult to find information on this. There is a lot about printing.

       

      Thanks in advance. Looking forward to the answer.    

        • 1. Re: Lightroom export page DPI settings for screen viewing
          JimHess Community Member

          You aren't going to see any difference. The monitor is going to display at its resolution regardless of what that setting is. In reality, the DPI or PPI setting is basically meaningless. Consider an image that is 4000 x 6000 pixels in dimension. Regardless of what that PPI setting is set to in the file, the image is still 4000 x 6000 pixels. The only real value there is to setting that resolution would be to allow a program such as Photoshop to report the dimensions of the image at any given PPI setting. The same is true for printing. If an image is 6000 pixels along the long edge, and you divide that number by 300 PPI, it would render a 20 inch print at that setting. So the debate will continue, and nobody will ever accept anybody else's answer because they are all convinced that they are correct.

           

          Generally speaking, when I export images from Lightroom I am primarily concerned about the number of pixels in the image. If I'm preparing images to display on the web or for e-mail I will usually specifies 72 PPI. But I do so realizing that it won't make any difference. I consider how large I want the recipient to be able to view the image and concern myself with ensuring that there will be enough pixels to do so.

          • 2. Re: Lightroom export page DPI settings for screen viewing
            digital paradise Community Member

            Thank you so much for the quick responce.

            • 3. Re: Lightroom export page DPI settings for screen viewing
              digital paradise Community Member

              Actually I have another question but it is not about resolution. According to some people somewhere Jeff Schewe stated this effected the sharpening algorithms. So because LR knows that it will be on screen which will be somewhere beteen 800 and 1200 on the long side (which is just an average) that it will sharpen differently as it resizes if you set the DPI to 100 as opposed to 300.

               

              Does that make sense?       

              • 4. Re: Lightroom export page DPI settings for screen viewing
                thedigitaldog CommunityMVP

                digital paradise wrote:

                 

                We are having a debate on another site about this. If you watch any Photoshop videos or look this up on the internet you will find that DPI has nothing to do with screen resolution, only print. If you select LR's web page it does not even offer a DPI setting.

                DPI and PPI or often used interchangeably so be careful. The D in DPI stands for dots, the P for Pixels. Printers don't make pixels hence the Dot terminology. But the tag, the value you set is rather meaningless. Digital images only have a size they take up on a storage device. The PPI/DPI values only allow us to extrapolate a 'size' if output using that tag and the number of pixels within a document. IOW, if you have 1000 pixels, 72ppi/dpi or 1000ppi/dpi make zero difference! The document is 1000 pixels along that one axis in both cases. You only now know that IF you divided your 1000 pixels by 72, would produce output (where?) that is 13.8 inches. Use the 1000 value, that falls to 1 inch. How do you wish to divide up the pixels you have into some size upon output and of course, what is the output device's resolution? It isn't 72 that's for sure in almost all cases. Even output to a display (my display's output resolution is 105ppi.)

                 

                You can export a document that's 1000 pixels and have a tag that states 72 or 1000, there's no difference at all in that document. The values are again, meaningless. But a value needs to be there and of course can be changed.

                • 5. Re: Lightroom export page DPI settings for screen viewing
                  dj_paige Community Member

                  digital paradise wrote:

                   

                  Actually I have another question but it is not about resolution. According to some people somewhere Jeff Schewe stated this effected the sharpening algorithms. So because LR knows that it will be on screen which will be somewhere beteen 800 and 1200 on the long side (which is just an average) that it will sharpen differently as it resizes if you set the DPI to 100 as opposed to 300.

                   

                  Does that make sense?       

                  I can't speak for Jeff Schewe. I will speak for myself.

                   

                  No, it does not make sense.


                  DPI has no effect here. DPI only effects printed images.

                   

                  Maybe you mean PPI, which does apply to digital images, but even there, I don't see how this could matter. Sharpening algorithms are applied to pixels, not PPI. An image that is 1200 pixels long side at 72 PPI is the EXACT SAME IMAGE with the EXACT SAME PIXELS as if you had changed the image to 1200 pixels long side at 300 PPI.

                   

                  You don't seem to have grasped this key point. Nor do you seem to have grasped the difference between DPI and PPI.

                   

                  Lastly, if someone is claiming that Jeff Schewe said something on this matter, DEMAND that they provide a link to Jeff Schewe's words on this matter. I am now making this demand of whoever said this, I am making this demand through you.

                  • 6. Re: Lightroom export page DPI settings for screen viewing
                    JimHess Community Member

                    digital paradise wrote:

                     

                    Actually I have another question but it is not about resolution. According to some people somewhere Jeff Schewe stated this effected the sharpening algorithms. So because LR knows that it will be on screen which will be somewhere beteen 800 and 1200 on the long side (which is just an average) that it will sharpen differently as it resizes if you set the DPI to 100 as opposed to 300.

                     

                    Does that make sense?       

                    The sharpening will have a different effect depending on the number of pixels in the image. But the PPI setting will make no difference at all. Sharpening effect on an image that is 1200 pixels will be much different than the sharpening effect on an image with 4000 pixels in that same dimension. But that PPI number, 72 or 300 or whatever, isn't going to make any difference on the sharpening effect. It is only a number. It has no impact whatsoever on the quality of the image.

                    • 7. Re: Lightroom export page DPI settings for screen viewing
                      thedigitaldog CommunityMVP

                      I will not speak for Jeff, he hangs out here but might be in 'book hell' (the reason he isn't heard from as often).

                       

                      Does LR sharpen based on the pixel dimensions? Yes. There is adaptive sharpening which I'm sure Jeff can better explain. This is based on the initial work of the late Bruce Fraser and described here:http://www.creativepro.com/article/out-of-gamut-thoughts-on-a-sharpening-workflow

                      LR is based in some part on Bruce's work here and on PhotoKit Sharpener. Not only are there multiple stages of sharpening but output sharpening takes into account, the pixel density of the image. A 1000 PPI image and one at 10,000 PPI are treated differently for output (which could be to screen). LR only considers two output sharpening targets however: Ink jet and screen. Contone, Halftone etc are not accounted for.

                      • 8. Re: Lightroom export page DPI settings for screen viewing
                        digital paradise Community Member

                        No I understand difference bwtween DPI and PPI dj_paige. I'm just taking about DPI and LR output sharpening and the claims people make. That somehow LR is special and the only software that takes into account that when you choose screen resolution it will sharpen differently based on a smaller image size like about 1000 by 1000 on average. I'm not making this claim but I have heard about it more than once so I decided to find that actual answer. I don't support this at this point. I believe it makes no difference.             

                        • 9. Re: Lightroom export page DPI settings for screen viewing
                          digital paradise Community Member

                          Wow Andrew. How are you? Many years ago you helped out quite a bit regarding which colour space to shoot at (aRGB) becuase you just don't how much more colour your printer can go outside the sRGB space. I think I go that right. It was on forums but I can't rememeber where. I did get your book Color Management for Photograhpers.

                           

                          Thanks for the reply.          

                          • 10. Re: Lightroom export page DPI settings for screen viewing
                            digital paradise Community Member

                            Just so every one knows I have studied the 3 phases of sharpening and put a lot of time an effort to develop my PP to acheive the results I want. I have my own output resizing and sharpening actions using edge sharpening in Photoshop which I use for my personal work. I use LR for mass edits and am very pleased with the results. I just prefer more control PS gives me for output sharpening. I'm just curious about this LR sharpening claim I have read about so many times.      

                            • 11. Re: Lightroom export page DPI settings for screen viewing
                              elie-d Community Member

                              Written by Jeff Schewe:

                              Source:  http://www.luminous-landscape.com/forum/index.php?topic=66916.0

                              Even if you don't "resize" in export you still set an output resolution...it is that resolution that impacts how the sharpening is applied when choosing screen matte or glossy. If you set the resolution to 72 (or 100) PPI then select a paper output sharpening you won't get a good result. Same as if you set the resolution to 360 and apply a screen sharpening.

                              And yes, the output sharpening in LR is based upon PKS inkjet and screen output sharpening but it was determined that a single sharpening designed for 72-120ppi was suitable for screen output sharpening so LR's output sharpening for screen is not size dependent, only resolution ppi.

                              I may be mistaken, but I understand from the above that although the ppi setting does not change the size of the image nor the way it is displayed on any given monitor, it does affect the nature of the output sharpening applied by LR or PKS and optimum sharpening on an image that is being downsized and is destined for the web is optained by putting a number between 72 and 120 in the ppi box. Am I wrong?

                              • 12. Re: Lightroom export page DPI settings for screen viewing
                                digital paradise Community Member

                                I'm not sure but it sounds like it to me. What does everyone else think? I don't want to get the person demanding things from me any more worked up.

                                 

                                Thanks very much for the link. I really appreciate it. I have been scouring the web for a couple of days but it is all about print. I did get a few hits at LL but it was some training videos I think.    

                                • 13. Re: Lightroom export page DPI settings for screen viewing
                                  digital paradise Community Member

                                  Life can be odd. The person on the other forum just posted this LL link the very same minute I did. It had been a few years so it took him a while to find it. Thanks again     

                                  • 14. Re: Lightroom export page DPI settings for screen viewing
                                    digital paradise Community Member

                                    I was going over this thread and realized I did make an error in my opening post. I don't know why I called it DPI, it should have been PPI. l used Canon's DPP for many years and they call it DPI which is the same thing. Guess I had blank moment. I do undertand the difference. My appologies for causing some confusion for part of this thread.