Skip navigation
Sheilaartist
Currently Being Moderated

Save 300 dpi jpegs

Jul 21, 2013 2:05 PM

I have a tiff file of a painting I scanned at 300 dpi. It's original image size when I open it is photoshop is 57.8 MB, 18" W by 12.477" H, Res 300. I need to resize it and send it as a 300 dpi jpeg. I have started in the image size dialogue box and just change the W to 11.25. That automatically changes the H to 7.798 and the res still says 300. The file size reduces to 22.6 MB. I click ok and then go to save as and choose jpeg. In the jpeg box I chose 12 Max and baseline standard and click ok. The saved file is reduced to 8.5 MB. When I open it in photoshop, it opens at 300 dpi when I look in the image size box. However, when I send it to someone else and they open it, the file is only 72 dpi. What am I missing to get the file to save at 11.25 inches, jpeg, but remain 300 dpi?

 

Thank you.

Sheilaartist

 
Replies
  • Currently Being Moderated
    Jul 21, 2013 3:48 PM   in reply to Sheilaartist

    You used Save For Web?

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 21, 2013 5:12 PM   in reply to Sheilaartist

    I took a 350 ppi PSD and saved it as a tiff and as a jpeg following your steps.

     

    Here's the problem. If your Jpeg is opened up in any other program but Photoshop, the document size is defaulted to 72 ppi. In other words your print info is not read correctly and defaulted to the web standard of 72 dpi. Corel Painter will do this as an example. If you have other graphics software other than Adobe you might see it read as 72 ppi too.

     

    If I save it as a Tiff, then the 350 ppi print info is preserved. That's why if your client wants to send it off to be printed, tiff is the way to go or if they have Photoshop,they should use it to open your jpegs if they want your intended print size and resolution.

     

    Gene

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 21, 2013 5:26 PM   in reply to gener7

    Any software that reads EXIF or XMP metadata should get the resolution right.

    But some older software, or software that doesn't read metadata, might get the resolution wrong.

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 21, 2013 6:07 PM   in reply to Chris Cox

    Reading metadata is uneven in progams like Painter. It will read tiff or psd resolution correctly but not jpeg. Well at least I know what's going on, so I can work around it.  I appreciate your input on this.

     

    Gene

     
    |
    Mark as:
  • JJMack
    6,017 posts
    Jan 9, 2006
    Currently Being Moderated
    Jul 21, 2013 9:28 PM   in reply to Sheilaartist

    I have a tiff file of a painting I scanned at 300 dpi. It's original image size when I open it is photoshop is 57.8 MB, 18" W by 12.477" H, Res 300.

     

    That means you image is 18x300=5400px wide and 12.477x300=3743px high  widthxheight=numbed of pixel 3 bytes per pixel for 8bit color 5400x3743x3=60,636,600 which is close to Photoshop 57.8MB estimate or the Tiff file is 57,8MB.

     

    I need to resize it and send it as a 300 dpi jpeg.

     

    Then all you have to do is resize the open document and save a jpeg file.

     

    I have started in the image size dialogue box and just change the W to 11.25. That automatically changes the H to 7.798 and the res still says 300.

     

    That means you also have RESAMPLE and Constrain checked in the Image Size dialog bottom control section and some interpolation method is set. Photoshop will reduce the number of pixels you have for the image. When you click on OK Photoshop will generate a new image that is  11.25x300=3375px wide and 7.798x300=2339px high

     

    The file size reduces to 22.6 MB.

     

    The file is not changed when you use Image Size.  The Tiff file remains as it was before it was opened. Photoshop is a document editor not a file editor.

     

    I click ok and then go to save as and choose jpeg.

     

    When you use "Save as" and use the pull-down menu and select Jpeg you will be saving a new file and not be over writing the tiff file.

     

    In the jpeg box I chose 12 Max

     

    That is a quality setting the higher the number (Max 12) the better the file quality will be the file will be less compressed then when lower quality setting are used.  You would be hard pressed to see any image quality difference between quality 10 file and quality 12 file.  The quality 10 file size will be quite a bit smaller then a quality 12 jpeg file.

     

     

    and baseline standard and click ok. The saved file is reduced to 8.5 MB.

     

    The new jpeg file size is a product of the jpeg quality setting and how well the image data compresses.  Size can vary all over the place.  Images with lots of fine details will be larger then images with little detail.  An image of a white wall will compress much smaller the an image with the same number of pixels that has a lot of details like an image of a cross word puzzle.

     

     

    When I open it in photoshop, it opens at 300 dpi when I look in the image size box.

     

    Correct you did not change the resolution when you resampled the image.

     

    However, when I send it to someone else and they open it, the file is only 72 dpi. What am I missing to get the file to save at 11.25 inches, jpeg, but remain 300 dpi?

     

    If when they open the file the receive they see an  image that has a 72dpi resolution. It means either what you used to send the file resized the the image and sent a different file or what was used to receive the file resized the image and saved a different file. Or the image was resized by the image processor the user used to open the file either during open or after it was opened.  For example if the user received the file you saved and sent 3375px wide and 2339px high and 300DPI and opened it in Photoshop and Photoshop is set to open Jpeg images through ARC the users ACR default workflow setting could be set to open image at 72DPI.  An image dpi is a setting the image may still be 3375px wide and 2339px high however set to 72 DPI the print size would be 3375px/72=46.875"  wide and 2339px/72=32.486" high  using Image size changing itr 72dpi print resolution to 300dpi with RESAMPLE NOT CHECK would return it size to 11.25" x 7.798" at 300DPI.

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 22, 2013 2:47 AM   in reply to Sheilaartist

    Sheila,

     

    PPI resolution is utterly irrelevant as long as the pixel dimensions remain exactly the same, i.e. so many pixels wide by so many pixels high, regardles of ppi.

     

    As long as that is what you are seeing, it doesn't matter in the least whether the ppi is getting changed for whatever reason.

     

    When you go to the Image menu > Image Size…, as long as you are careful to make sure that the "Resample" box remains UNCHECKED, you can change the ppi resolution to any number of values you wish and you'll see that the pixel dimensions (width x height) remain the same.  The pixels have not been touched at all.

     

    What is important is NOT to open the image to re-save it just in order to change the ppi resolution.  The reason for this is a CRITICAL principle:

     

    Any time you open and re-save a JPEG, even if you make absolutely no changes to it, the image file gets compressed all over again, every single time without exception, and the quality of your image deteriorates every time, over and over again, every single time, without exception.

     

    The best strategy is to work exclusively on PSDs, PSBs and TIFFs, and only generate the lossy JPEG at the very end of your workflow in order to generate the target JPEG you will never, ever re-save again.

     

    My personal policy is to avoid JPEGs scrupulously, unless and until someone specifically asks for or demands one—like your magazine does.  Then I just save a copy of my working PSD or PSB, and never re-save it again.

     

    It's OK to open and close it without saving or re-saving.

     

    Of course, I make sure that all my files are always tagged (i.e. they have their intended color-space profile embedded—even the lowly JPEGs.

     

    One last caveat for all Mac users

     

    BEWARE of Apple's Mail program.  When you send an unarchived (un-zipped or un-stuffed) image file, that dumb Apple Mail program WILL very often (always?) re-size your image by downsampling it (i.e. discarding a bunch of pixels) and substantially lowering the size and quality of your image.

     

    For that reason, I never touch Apple's Mail program.  Thank you for Entourage, Microsoft.

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 22, 2013 2:53 AM   in reply to Sheilaartist

    This is a link to an excellent scanning tips web site. 

     

    Even for users who never scan anything, this site contains the best explanation of ppi, dpi and spi I have ever encountered in the Internet.  I even bought the printed book edition myself, which essentially mirrors the web site:

     

       http://www.scantips.com/

     
    |
    Mark as:
  • Currently Being Moderated
    Jul 22, 2013 7:00 AM   in reply to Sheilaartist

    To avoid that issue with email applications even if it is just one image file I recommend Zipping it first. I prefer to use 7zip as it works well on both Mac and PC.

     
    |
    Mark as:

More Like This

  • Retrieving data ...

Bookmarked By (0)

Answers + Points = Status

  • 10 points awarded for Correct Answers
  • 5 points awarded for Helpful Answers
  • 10,000+ points
  • 1,001-10,000 points
  • 501-1,000 points
  • 5-500 points