Free Transform Loss in Quality

Discussion in 'Design and Graphics' started by oldschool, Aug 13, 2011.

  1. oldschool macrumors 65816

    oldschool

    Joined:
    Sep 30, 2003
    #1
    I have a photo that was taken with an SLR at 72 DPI JPG. I need it at 300 DPI for print, and at a much smaller size, so I changed the DPI in "image size" without resampling. Then I added the other elements needed for the mockup and had to change the size of the image using free transform. When I zoom in now the image becomes pixelated much earlier. Will this show up in print or am I just stupid and missing something?
     
  2. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #2
    Whether your photo was taken at 72 dpi or 300 dpi is completely and totally meaningless. Nobody measures the resolution of digital photogaphs this way. It is common practice to measure photographs by the number of pixels in the image. Let us say that your camera can produce an image that is 4800 pixels by 3000 pixels. The image is 4800x3000 = 14.4 megapixels. This would be an 8"x5" photograph at 600 dpi. However, it would also be a 16"x10" photograph at 300 dpi or a 4"x2.5" photograph at 1200 dpi.

    Virtually any application that handles raster graphic images can magnify or reduce the physical size of a photograph without changing the number of pixels in the image.

    Meaningful information:
    • The source of your photograph.
    • The physical dimensions of your photograph such as 3"x5," 5"x8," "8x10," etc.
    • The number of pixels in your image such as 5 MP (megapixels), 8 MP, 12 MP, etc.
    • Monochrome or color. Human vision is more tolerant of low-resolution color than it is of low-resolution monochrome.
    If your photograph is a small low-resolution scan, then your best bet is to rescan it. If you don't have the original, then there is little that you can do. However, little is not the same as nothing. There are fractal-based Photoshop plug-ins that allow you to magnify raster images while minimizing perceived blurriness.
     
  3. Dark slide macrumors newbie

    Joined:
    Mar 15, 2010
    #3
    re: free transform loss in quality

    Try converting the image you need to transform scale into a "smart object" first. (in ps5, that would be: Layer > smart objects > convert to smart object) Then you can do the transforming with better results.
     
  4. Nostromo macrumors 65816

    Nostromo

    Joined:
    Dec 26, 2009
    Location:
    Deep Space
    #4
    DSLRs don't take photos at a certain dpi.

    It's a setting that you can use in your RAW processor when you convert the RAW to TIFF or JPEG.

    Your 72dpi image is not the original. Go back to the original.

    PS: dpi only matters for print. It has no influence whatsoever on online display (even though everybody recommends to put your images at 72dpi online).
     
  5. Mutinygraphiks macrumors regular

    Mutinygraphiks

    Joined:
    Jan 5, 2011
    Location:
    Las Vegas, NV
    #5
    the only reason this is done is because 72dpi allows for original quality at a small size in file.
     
  6. designguy79 macrumors 6502

    Joined:
    Sep 24, 2009
    Location:
    Michigan
    #6
    Sorry, not true.

    DPI is a term of measurement for a device, not an image.

    The same JPG file "at 72 dpi" and "at 300 dpi" are identical on your computer.

    Read this -- it is not short, but thorough, and includes examples. Or Google "DPI myth."
     
  7. Mutinygraphiks macrumors regular

    Mutinygraphiks

    Joined:
    Jan 5, 2011
    Location:
    Las Vegas, NV
    #7
    when it comes to importing files onto a website say a custom one with limited server space 72 dpi photos are small kb sized files this is my reference.

    so for you to tell me they are identical they are not in the least bit as far as storage size, but as far as quality could be comparable.
     
  8. designguy79 macrumors 6502

    Joined:
    Sep 24, 2009
    Location:
    Michigan
    #8
    Did you read the article I linked to? :D

    I am struggling to explain this -- anyone care to back me up?

    Let's take an example -- a 200 by 200 pixel photo "at 72 DPI" and a 200 by 200 pixel photo "at 300 DPI" will be the exact same filesize (if saved with the same compression settings, e.g., JPG quality)

    ----------

    I think the confusion on this relates to the way the "Image Size" works in PhotoShop.

    If you leave the "Resample Image" box checked, and modify the "Resolution" from 300 to 72, it changes the pixel width and height. (of course, changing it from 72 to 300 also does that)

    If you un-check the "Resample Image" box and then change the "Resolution", you can see that the file size doesn't change at all (thus proving the point).

    Hope that helps clear it up a little better. Give it a try for yourself if you don't believe me!
     
  9. brisbaneguy29, Aug 24, 2011
    Last edited: Aug 24, 2011

    brisbaneguy29 macrumors 6502

    brisbaneguy29

    Joined:
    Nov 27, 2007
    Location:
    Brisbane
    #9
    You are 100% correct. DPI is meaningless in the web world. ALL that matters is the actual pixel dimensions and the compression you apply to that image. DPI is an output resolution and is only applicable when printing.

    <rant>And another thing, why do people continue to say i am saving my photos at 72dpi. Your not. You can save them at 72ppi. DPI is Dots Per Inch and is an output resolution used by printing devices. In Photoshop you set your images to PPI, or Pixels Per Inch. I hate seeing people say a digital images use DPI, they don't, your printer does.</rant>

    As for the original posters question, if you changed the DPI size for print, without resampling, you have not lost any information in the image, and the quality is unaffected. As long as when you print the image you don't try and print at 200% you should be fine.

    What concerns me is what you did during free transform. If you pulled the image up trying to make it bigger ( like zooming in on a section of the image), you might run into issues. Increasing the size like that, means photoshop essentially has to make up the pixels to make the image larger, and this will give a substandard result. You really cannot make the image any bigger than it originally was. If it was 3000px x 4000px, that is the max size it should be used at. There are funky plugins that help you get away with upscaling an image but in the long run all you are doing is filling in the blank spaces with interpreted data.
     

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