dpi question

Discussion in 'Beyond the Basics' started by tonyadgarcia, Feb 26, 2009.

  1. tonyadgarcia

    tonyadgarcia TPF Noob!

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    how come every picture has a dpi of 72? thats not a high enough number for a good quality photo right? how do i change that> i have a sony a350
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Firstly, it's actually PPI (pixels per inch) not DPI (dots per inch).

    Secondly, that is just a default value. It's the typical screen resolution for a monitor...so that's why it's a default.

    Lastly, it's mostly a meaningless number when talking about the quality or resolution of the actual image. You could change it to 50 or 5000 and if that is all you change...it won't change the image at all. It just tells the computer how big to display it on the screen.

    The important number is the size of the image in pixels. As long as you have enough pixels...you will be OK for printing.

    To make things easier for yourself...you can change the PPI number to 300 (without resampling) and then everything should fall into place.
     
  3. tonyadgarcia

    tonyadgarcia TPF Noob!

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    thanks so much for the info. so how do i change the ppi? the deeper i get into learning this, the harder it seems but makes sense once i get advice.i love photography and new there was more to it than just taking a photo but damn its hard to understand it all in their words.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    What editing software do you have? You should be able to change the PPI with your software.
     
  5. tonyadgarcia

    tonyadgarcia TPF Noob!

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    adobe photoshop 7
     
  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    OK. Under the 'Image' menu you will find 'Image Size...' so open that up.

    Uncheck the 'resample' box, then change the PPI to 300. Done and done.
     
  7. adamwilliamking

    adamwilliamking TPF Noob!

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    Haven't used 7 but if its anything like CS you can find the PPI vale in the "Image Size" settings.

    Edit; Mike is just way too fast for me.
     
  8. Katier

    Katier TPF Noob!

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    Actually PPI and DPI are essentially the same thing.. HOWEVER DPI is the more correct statement because it's fair for screen AND print.

    PPI is a Pixel.. don't get pixels in printing.. so using DPI is the best format as a pixel is a dot of light.. and in print a dot is a dot of ink.. so DPI works fine for both.

    What the software uses varies but Quark uses dpi mainly because it's intended for print.
     
  9. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I don't consider a pixel and a dot to be the same thing...but to simplify things, they can be used interchangeably in some situations...mostly because people have been mixing them up for so long that their meanings have become muddy.
     
  10. Katier

    Katier TPF Noob!

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    Well I'm not sure how they're not the same thing, unless you REALLY want to split hairs as a Pixel is technically 3 dots ( Red Green Blue ). HOWEVER screen ( where PPI is arguably more correct ) their is only one setting - 72.

    Print ( where it's definatly DPI ) is where the setting truly matters so it's better overall to use DPI as queries and settings regarding the resolution of an image invariably related to print because on screen we'll often look at an image zoomed or at full rez but not realising screen is a lot lower ( i.e. a 10x8 image on the screen @ 100% coming out crap on paper).

    Therefore usually when answering questions DPI is usually correct NOT PPI due to the questions usually being related to print not screen. :p
     
  11. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    The initial question had nothing to do with prints.

    To me, a pixel is a bit of digital information that is has been assigned color and location. Call it a 'dot' if you want. I really don't want to argue about it.
     
  12. Katier

    Katier TPF Noob!

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    Depends if your working for screen or print.

    72 is the default dpi of a screen. Print needs a minimum of about 150-180 for decent quality, preferably more ( 300 is the default used for professional newspapers and magazines).

    So for screen 72 dpi is fine, that said I suspect your camera is using a 'default' number and that your image will print just fine if that is your intention. The easiest solution is to take the resolution of your images ( for example 1500x1500 pixels ) and divide by the resolution you want ( say 300) so in this case your image would print fine at 5x5 inches at 300 dpi or 10x10 at 150dpi ( which would be borderline good quality) even if the image has been saved with the dpi setting at 72.
     

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