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Changing dpi in photoshop


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#1 rodent

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    Posted 16 November 2007 - 05:11 PM

    I have a picture that is 72dpi, so the resolution isn’t high enough to use in a photobook I’m making. In photoshop, I can change the dpi to 150. After I do this, shutterfly says the picture is good enough to print up to 11x14. Previously it was only recommended for a wallet print. So is the picture now a higher resolution? Will it actually look nicer now that I changed it to 150 dpi?

    I want to take a bunch of my friends pictures off facebook & make her a photobook with them. They are only 72dpi on facebook.

    #2 cheese_diva

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      Posted 16 November 2007 - 05:17 PM

      Unfortunately web images will not print nicely... 300dpi is preferred and unless your images was 300 dpi or higher, you can't add resolution to a picture.. In other words, you can't add dots or details to a photo that doesn't have it to start.. 72 dots per inch won't look good.
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      #3 rodent

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        Posted 16 November 2007 - 05:23 PM

        Quote:
        Originally Posted by cheese_diva
        Unfortunately web images will not print nicely... 300dpi is preferred and unless your images was 300 dpi or higher, you can't add resolution to a picture.. In other words, you can't add dots or details to a photo that doesn't have it to start.. 72 dots per inch won't look good.
        I didn't think you could add quality to a picture when it's not there, but when I do the steps it acts like it's fine. But then I don't want to make an entire book that will look bad. I might order a 5x7 print to see what it looks like.

        #4 rodent

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          Posted 16 November 2007 - 05:30 PM

          I found this online:

          When changing resolution, PhotoShop runs complicated algorithms on an image to decide exactly how to change it. PhotoShop does an amazing job of adding and subtracting pixels, but it isnt magic. Usually you can only move up or down in resolution by about 1/3 before the image really suffers.


          So it sounds like photoshop can actually take a web image and make it the resolution needed to make a decent print. These don't need to be amazing pictures. I am also changing them with the artistic effects to look like a painting, so they don't need to be perfectly sharp.

          I know 300 dpi is ideal, but I've made some photobooks with the pictures at 200-250 dpi & they look good. So I'm thinking I'll change my 72s dpi pictures to around 200dpi. Sounds like changing it to 300 is pushing it too far.

          #5 rodent

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            Posted 16 November 2007 - 05:43 PM

            All About Digital Photos - The Myth of DPI

            I found some other info, but I can't read it all right now. I have a lot to learn about dpi, resolution, etc.

            #6 jthrasher

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              Posted 16 November 2007 - 06:11 PM

              DPI is all relative if you don't know the resolution or dimensions of an image. DPI, or PPI is just how many dots or pixels per inch the photo will print at.

              You can have a photo that is 72dpi and 300dpi but have them be exactly the same file size. However, their dimensions or resolution will be completely different.

              For example I have a photo I'm looking at the is 72 PPI (pixels per inch) and the resolution is 2912x4368. If I print it out at 72PPI it will print at 60"x40"

              60"x40" is huge and I don't want to print it that big so I go into image size to change the size. Plus if I print the photo that size and only 72 pixels per inch, it will be bad quality. When I go into image size and If I have the resample image box unchecked and change the PPI to 300, The new output print size is 9.7"x14.5". But, the resolution is the same 2912x4368. So, the file size didn't change. If I try to make a print bigger than 9.7"x14.5 inches at 300ppi, the image is going to start to look bad.

              If I try to change the resolution to 300 and the resample image box is checked, the resolution becomes 12133x18200. You're telling Photoshop that you want to try and keep this image's output size at 60"x40" but instead of 72ppi you want to make it 300ppi so it has to add a lot of pixels that aren't there. So, it does it's best at guessing and filling in pixels based on the color of the pixels it's putting the new pixels next to. Thus the image isn't the greatest quality because the new pixel information added isn't "real".

              I know it's all very confusing. Here is a good article that explains DPI and resolution. resolution and DPI explained

              #7 jthrasher

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                Posted 16 November 2007 - 06:15 PM

                Quote:
                Originally Posted by Morgan
                All About Digital Photos - The Myth of DPI

                I found some other info, but I can't read it all right now. I have a lot to learn about dpi, resolution, etc.
                ha. that's even a better article than what I posted. :-) thanks!

                #8 rodent

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                  Posted 16 November 2007 - 06:19 PM

                  Thanks a lot Jonathan. I think having photoshop guess the pixels will do the trick for my project. I will be doing photoshop effects like cutout & drybrush with these pictures, so the accuracy of the pixels won't be as important. These are mostly pictures of buildings and parks. My friend lived in London last year & I want to take her snapshots off facebook and put them together in a coffee table style book.

                  #9 rodent

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                    Posted 16 November 2007 - 06:23 PM

                    Quote:
                    Originally Posted by jthrasherphoto.com
                    ha. that's even a better article than what I posted. :-) thanks!
                    I read that article right after I started this thread & realized I should stop throwing around terms like resolution & dpi until I really understand what I'm talking about. I just started using photoshop a couple months ago, so I have a lot to learn about digital images. But, it has been fun learning. Everyone around me gets surprise photo projects as I learn new techniques.

                    #10 Maggie&Darryl08

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                      Posted 17 November 2007 - 06:47 PM

                      This is so funny. I am making a photobook for fiance for xmas and I am using photoshop which I have only been playing with for a couple of months too. Today I had to increase the resolution in a couple of photos to make them acceptable in shutterfly and they look okay. We'll see how it looks when I get the printed copy back. Yikes.

                      I like these threads....I have no idea about resolution, ppi etc etc.....

                      I love the photoshop tips, it really helps.




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