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DPI, Printing and Pain Shop Pro 8 Query

Discussion in 'Photography Forums' started by Kevo, Aug 28, 2005.

  1. Kevo

    Kevo
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    My old compact digital Camera (3mp) defaults to 72 dpi, which as you know is too small for a 6x4 photo print.
    Which means in Paint Shop Pro 8 I have to change this setting to 200-300 (in 'Image Resize') every time I want to print...or do I?

    (Assuming the pic is taken at a large enough res)
    What if I leave it at 72 dpi and adjust it to 6 x 4" (or near as) in the 'Print Layout' view?
    There's nothing in this view to say what the DPI is?

    Similarly if I was to print it in MS Word and resized it down, would the software in each case auto adjust the 'optimum dpi' setting or does it always use what is saved with the image file?

    Also, why default to 72 dpi anyway, if this setting is only relevant to the printed version, why not default to at least 200dpi? There's no way of changing it in camera and it's a 3mp so should hold it's own at that res.
    Do more modern compacts default to a higher res? My Nikon D70, whichs is a DSLR defaults to 300dpi (the 'human optimum').

    Many Thanks
     
  2. severnsource

    severnsource
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    Forget about dpi in this sort of case. To all intents and purposes it is a random number that is pretty well irrelevant to printing. For instance I've just loaded a 3M pixel image in PSP7 and the information box gives a dpi of 72, but if you look at the image size, this is given as 28" x 21", in other words a pretty big print.

    In PSP just adjust in the print settings dialogue box, as you say. AIUI in Word the original file is kept unchanged and Word scales its version of the image.

    I think that the 72 dpi originates in display resolutions, they are usually between 72 and 100 dpi.

    Bill
     
  3. Kevo

    Kevo
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    Thanks severncourse

    I'm sure i've read somewhere that inkjet printers will use the dpi setting saved with the image file and go off that when printing at it's dpi.

    e.g. if the file is set to 300dpi and the printer to 1440dpi then it will use 1440 (blended) dpi to produce the colours @ 300dpi?

    Or am i way off the mark?
     
  4. Alan D

    Alan D
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    This article might help
    http://www.rideau-info.com/genealogy/digital/dpi.html

    And, from a different source:

    Dots Per Inch (DPI) vs. Pixels Per Inch (PPI)
    DPI and PPI are probably confused more than any other term in digital photography because they sound so similar. The good news is the difference is simple to understand.

    Pixels Per Inch or PPI refers to how closely pixels are packed together in an inch of space. It doesn't matter whether you're talking about a screen or a printer.

    Dots Per Inch or DPI refers to how many dots a printer uses to create a single pixel when it's printing one of your photos. If you sent a 240 ppi image to a 720 dpi printer each pixel will be represented by 3 tiny dots on the paper. A 2880 dpi printer will use 12 tiny dots of ink to represent each pixel.

    Why is this important? In theory, when a printer can use more dots to create a single pixel, it can represent the color of that pixel more accurately on the paper. That means the printer can create prints that are seamless in continuous tone areas. You probably remember seeing digital prints a few years ago that had visible bands in the sky. That's because the printer didn't have enough resolution, or dpi, to accurately represent all the colors required to accurately represent the smooth tonal changes across the sky.

    You can see a difference between prints done at 720 dpi and 1440 dpi. But that difference gets a lot harder to see between 1440 dpi and 2880 dpi. So a lot of photographers use the 1440 dpi setting on their photo printers to save time (faster printing) and money (you use a little less ink).
     
  5. Alan D

    Alan D
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  6. Kevo

    Kevo
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    Thanks Alan

    I've read that article before and very informative it is too.
    It is in fact where I got myinfo from about inkjet printers using "it's dpi against the image file's dpi"

    From the article...

    It's that 'render 300' part which is confusing.

    Basically, do I need to change this DPI setting from 72dpi to 300dpi in PSP8 in the 'Image Resize' options everytime or will simply changing the physical size in print layout view suffice ?
     
  7. severnsource

    severnsource
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    No, just change the size in print layout view. The printer driver does the rendering, and modern printers and printer drivers do a fine job of printing without the user getting involved with the fine detail.

    The trouble is all this nomenclature mainly seems to produce confusion. The picture off the camera sensor has no inherent resolution in terms of DPI, it is just a picture with an array of say 1600 by 1200 individual elements in it. DPI only starts to become relevant when the image is displayed somewhere, so to label an image as being 72 dpi or 300 dpi from the camera is completely meaningless and irrelevant.

    Printer dpi is another completely confusing can of worms. When a printer specifies a resolution of say 1440 dpi this means that it can lay that many dots of each of its inks in a line. Unfortunately the printer will only have at the most 8 different coloured inks to produce a continuous tone image, in order to produce an illusion of continuous tone the printer has to lay down a combination of several dots of each colour - usually known as dithering - this process reduces the actual resolution capability of the printer significantly. It also means that there is no relationship between the printers quoted resolution and the resolution that you end up with.

    Bill
     
  8. Kevo

    Kevo
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    Thanks Severn

    Think I've got it now.
    I've only recently got to grasp what DPI in was all about as I've never really printed off much many photos.
    It's just this final bit with the printer's dpi and the dpi (variable) that is stored with the file that was confusing me.

    So in PSP8 where it does allow you to change the DPI is simply a variable only and is used as a kind of reference in relation to the physical printed size?
    Likewise if I change the physical dimensions then the dpi will change accordingly.

    Cheers all
     
  9. severnsource

    severnsource
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    Yes, that's my understanding of it.
     
  10. MattB1

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    Hi,

    When resizing down in PSP always increase the PPI first (in image resize) to anything above 300 then after you have done that change the dimensions. If you leave it at 72 and resize down the quality will be poor. If you change teh ppi to a large number PSP will adjust it down (although ot won't change in the text box) according to teh dimensions that you put in for the picture.

    It's easy to see the difference. Just print one pic at 6 * 4 at 72 ppi and teh same pic at 300ppi.

    Matt.
     
  11. longleyc

    longleyc
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    Thats good advice from all the above posts.

    The reason that the default is 72 dpi relates back to the early days of computing where monitors were 72pdi display. Some were 96 dpi.

    Adjusting the dpi in software is useful. When I say dpi read ppi. Its a tad confusing to the beginner but reading the info on it should have given you a better reasoning behind it.

    By altering the dpi/ppi you can effectively spread those pixels in the image over the print size you wish. Lets say a 3mp image at 300dpi/ppi = 6x4 image, if you set a 200dpi/ppi you can print an 8x6. You are in control.
    Those auto fit to size just do that, automatically fit the dpi to the print size.
    Larger images of 8mp may show high dpi/ppi of 350+ if printing to 6x4 size but thats not important if its too large. True photo quality is around 300 dpi, more than this the eye cannot tell the difference.
     
  12. Kevo

    Kevo
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    Agreed, i've read several articles on the subject and all try and explain it in their own ways (some more confusing than others!), but reading all the replies here DOES clear it up.

    For instance, longleyc...

    Obvious really, but only when you word it simply as you have here and don't go round the houses :thumbsup:

    Thanks to all :smashin:
     

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