Image Resolution and Printing

Discussion in 'Photography Forums' started by Matt F, Aug 29, 2002.

  1. Matt F

    Matt F
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    I was reading an article in a digital camera magazine the other day where they compared printing the same image at different resolutions.

    Now, they used an Epson printer that printed at 1440dpi - dots per (square) inch I presume. They concluded that there was no point in a picture being any more than 300ppi (pixels per inch?) because after that there is no visual improvement.

    This confuses me a little - if the printer can print at 1440dpi then surely it is capable of showing the differences between an image with a resolution of, say, 1200ppi over an image with a resolution of 300ppi? If 300ppi is as detailed as the eye can see then why have printers that can print at 1440dpi and above?

    Can someone explain please.:confused:

    Thanks,

    Matt.
     
  2. MikeyB

    MikeyB
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    I'm no expert on these things, but all I know is this:

    My Lexmark printer has 2 resolutions, 600dpi & 1200dpi.

    I can easily see the different between 600dpi in its "best" mode (it has 3 modes), and 1200dpi (which only has a "best" mode!)

    Paper also makes a big difference to the print quality, 1200dpi is best on glossy paper.
     
  3. JSW

    JSW
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    Any res is better on glossy paper even 72 dpi
     
  4. Matt F

    Matt F
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    Thanks for the replies guys but the question still remains:

    If a printer can print at 1440dpi, why is there apparently no benefit in printing an image that (itself) has a resolution of anything greater than 300ppi?

    In other words - why wont you see the benefits of an image with a resolution of 1200ppi on a 1440dpi printer? Or will you?

    Matt.
     
  5. Guest

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    Don't know if this is correct but just a thought. Even with a 4 megapixel camera the image is only about 2200 x 1700 if you are printing at 7ins x 5ins then the 2200 pixels equals 314 pixels per inch (2200/7) therefore 300 dpi is about the resolution of a 4 megapixel image so printing at 14400 dpi will not result in greater clarity.

    Hope this helps.
     
  6. Kevo

    Kevo
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  7. michaelab

    michaelab
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    There's a lot of confusion about this. Firstly, DPI/PPI is totally meaningless for an image file on it's own as the size of the image depends on the resolution and size of the monitor you're looking at it. At best it's only useful in a scanned image to give any display or printing software a guide to how big the original scanned (hard copy) image was.

    Printer DPI (dots per inch) also doesn't have a great deal to do with image DPI. Inkjet printers need to get as high a DPI as possible in order to minimise the visibility of the physical ink dots on the paper and to get smooth colour/shade gradients. This DPI has nothing to do with image DPI though. My HP PSC 950 has a 2400 dpi printing mode, but that doesn't mean that a 2400 pixel image appears 1" wide on the paper!

    Dye sublimation printers (eg Olympus P400) on the other hand have far lower DPI (300 is typical) because they don't have any dot structure to try to hide and they produce FAR superior results to any inkjet printer.

    So to summarize, a digital camera image has no inherent 'size' but the more pixels the better obviously - this applies regardless of the printer you're printing it on.

    For inkjet printers, the higher the dpi the better - but you can't compare inkjet dpi with dye-sub dpi.

    Clearly, if you're using a 1200 dpi printer to print a 6x4" print from a 2048x1536 (3 megapixel) digicam image then the printer internally will have to interpolate that image up to 7200x4800 pixels some printers do this better than others and in many cases it's better to do this in software beforehand.

    For something like the Oly P400 which has 314 dpi a 4-5mp digicam image is at a higer resolution than the printer (for a 6x4 print) - the opposite situation with the inkjets. In this case the image needs to be downsampled before printing. Again, you may get better results using software.

    If you use something like QImage Pro from www.ddisoftware.com then you'll never have to worry about any of this. It's easily the best digital image printing software out there and you never ever have to think about DPI again!

    Michael.
     
  8. richard plumb

    richard plumb
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    my Sony 505V produces approximately1800x1200 images after cropping, and these make great 6x4 prints. I've even got one blown up to 12x8 and it still looks fantastic.

    In terms of computer resolution, 150dpi+ is best. Aim for 300 if you can (so for a 6x4 inch print, 1800x1200).

    Bear in mind that each of those computer pixels is full colour.

    For a printer, each dot can only be one colour (cyan, magneta, yellow or black), so they need to mix four colours to make a 'real world' colour. Hence the need for more dpi on printers than the original image.
     

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