resolution in photoshop

Discussion in 'Beyond the Basics' started by Skyeg, Mar 30, 2004.

  1. Skyeg

    Skyeg TPF Noob!

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    when i use photoshop it usualy says resolution 72dpi. why would i change that? and what would happen if i changed it?
     
  2. markc

    markc TPF Noob!

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    That's a tricky subject. One that many people misunderstand. The thing would be to read up on how dpi, number of pixels, and print(or display) size all relate. It's a three-way relationship where if one changes, at least one of the other two have to also. Having only one of the numbers tells you almost nothing. Say an image is 300 dpi, or 8x10 inches, or 2400x3000 pixels tells you nothing about the quality. If you say it's 8x10 at 300 dpi, then you know it's a decent image. If it's 300 dpi and 1x1.25 inches, it's only a 300x450 pixel image. That's fine at that small size, but sucks when you try to blow it up. Then it becomes an 8x10 at 37.5 dpi. Not good at all for printing.

    http://www.photoworks.com/Support/Lessons/Resolution101.aspx
    http://www.photonetwork.co.za/enquiries/articles/digital_images.htm
     
  3. Skyeg

    Skyeg TPF Noob!

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    so when i get images off my camera why are they 72dpi? can i just change it to 300dpi?
     
  4. jack

    jack TPF Noob!

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    hiya guys
    im sitting working on some pre-press materials right here.
    skyeg - one thing to be familar with is your images are 72 PPI
    rather than DPI. for print you might be wanting to post-produce (and size)
    your images in photoshop and export them in the best format for printing
    into illustrator. in illustrator, you establish the output resolution you
    require. (PDF, TIFF) EPS doesnt look great with 72ppi.

    also - in photoshop : FILE>COLOR SETTINGs go through these and
    make them appropriate for what you are trying.

    i'm trying to digest the washington post submission specs for media,
    i'm looking for a PPI benchmark too, for semi-glossy papers at
    600dpi. if i experiment and raise my PPI in photoshop, the image
    increases massively in pixel area, and the file is like 1.1 jig which is
    ridiculous!. (i think i read somewhere that 100ppi is the minimum spec
    for newsprint .. dont quote me , ill try to check that :0) (?) maybe that
    was 100LPI . hmmmmm

    take a look - its closely related to your questions, and also it can
    give you some template sizes for press-ready artworks that will
    fit with what customers need - if your offering press-ready media.


    search through the sections :0)
    http://advertising.washpost.com/ad_specs/mechanical_specs/color_specs/color_specs.jsp
     
  5. jack

    jack TPF Noob!

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    thats a good glossary actually !
    http://advertising.washpost.com/ad_specs/sending_digital_files/glossary.jsp



    ""
    dpi (dots per inch) and ppi (pixels per inch)
    Dots and pixels are not the same thing: dpi is a measurement of printed dots per inch on a paper and ppi refers to the number of picture elements (pixels) gathered by a scanner or viewable on a screen. There is no correlation between the resolution of digital data (ppi) and the reslotion of a printed image (dpi).
    ""
    http://www.color-printing.com/inkjet-dpi-vs-ppi.html
     
  6. jack

    jack TPF Noob!

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    all you need is to find a happy compromise between the
    pixel-count and a desired size of printed repro.

    you have a 72ppi image - if you make it 100ppi, it doesnt alter the
    visual definition, just makes it larger (on-screen). you need a software
    application (like illustrator) which can instruct a printer to repro at your
    chosen DPI (dots of ink per inch )


    this subject is the main stumbling-block in my world at the moment.
    any input that anyone can add to what has been noted, please jump
    right in :0)



    EDIT: skyeg - im going to open a 3000x2000pixel, 72ppi neg scan
    (TIF file). then i will 'up-it' to 100PPI and pre-press it in the normal way
    into a sized placed-file in illustrator and see if its any higher-definition than
    the existing 72PPI. i'll let you know.
     
  7. Cuervo79

    Cuervo79 Guest

    well if you blow it up from 72 to 300 it wont make any diference other than the visual size in your monitor, also photoshop is "guessing" on when you try to give it more resolution, because the data isn't there, I personally ask what's the dpi of the printer and work on with the double of the resolution, if the printer is 150DPI i work with 300DPI, I've heard from allot of ppl that tha's the way to go.
     
  8. Skyeg

    Skyeg TPF Noob!

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    ok, im confused.....so i open an image that i just scanned or took with my digital camera, in photoshop, im planing on printing an 8x10. i resize the photo to 8x10 but should i leave the pixles per inch 72? or should i change it?
     
  9. markc

    markc TPF Noob!

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    I never change the pixle count, which will happen if you change both print size and dpi. Just change the print size to what you want to print without resampling. If the DPI gets under 300, then you start to lose quality and you might want to rethink the size of the print, but if it looks okay to you at 100dpi or whatever, then don't worry about it.

    Never resample unless you are making an image for the web, in which case save the web image as a different file.
     
  10. voodoocat

    voodoocat ))<>(( Supporting Member

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    Well 267 dpi is full resolution for printing, but everyone rounds up to 300.
     
  11. markc

    markc TPF Noob!

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    Do you mean for what the human eye can see?
     
  12. voodoocat

    voodoocat ))<>(( Supporting Member

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    That might be it. But I've always heard 267 was the actual dpi for printing but just to round up to 300.
     

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