Resolution, Image Size

Discussion in 'Beyond the Basics' started by cap1957, Oct 14, 2006.

  1. cap1957

    cap1957 TPF Noob!

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    Why is the resolution, or pixels-per-inch of digital cameras, so low? My Olympus Camedia C-5000 is only 144 ppi in TIFF format, and only 72 ppi in JPEG format, although the maximum image size is 2560 x 1920. When printed out, the files look a bit grainy, even the TIFFs, and after they have been resized to a smaller size too.

    When I scan in photos on my scanner, I always set the resolution to 300 ppi, which I think is the minimum resolution for good quality photos. So why aren't all digital cameras at least 200 or 300 ppi?

    What is the minimum adequate digital camera ppi for taking photos that are going to be converted into large posters, about 3 feet wide and tall?
     
  2. forceflow1049

    forceflow1049 TPF Noob!

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    Most jpegs are stored at 72 dpi, but you don't need to use this to print. Most programs allow you to choose what resolution to print at. I use 150-300 dpi, depending on what i'm doing.
     
  3. W.Smith

    W.Smith TPF Noob!

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    How sharp do you want it to be at what viewing distance, cap?
     
  4. cap1957

    cap1957 TPF Noob!

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    It should be high quality and sharp, not grainy, at any distance, if possible. These posters will be mass-produced and sold, if all goes well.
     
  5. LWW

    LWW TPF Noob!

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    You don't have enough horse to pull your wagon.

    LWW
     
  6. W.Smith

    W.Smith TPF Noob!

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    Please define the minimum distance you want it to be 'high quality and sharp'. Precisely. In inches or centimeters. That'll determine the required resolution. When you know that you can calculate what pixelsize, width x height, or how many megapixels the original for your 3'x3' poster must be.
     
  7. Flash Harry

    Flash Harry TPF Noob!

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    change your res on the originals to 300ppi in PS but leave image size as is, then you need to interpolate upwards to your required size, if the image starts to pixelate in PS before the required size then you'll need to invest in a program such as genuine fractals, or, buy a better camera.
     
  8. Flash Harry

    Flash Harry TPF Noob!

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    EDIT THE LAST POST: just looked up the camera, and LWW is correct, your camera isnt up to the job.
     
  9. Big Mike

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

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    I agree...you will have trouble making large prints with files from your camera.

    You want sharp prints that are 3 feet. That's 36 inches...at 300 PPI that is 10800 pixels. You are working with files that are 2560 on the biggest side.

    You can use software to interpolate the image...but that will loose quality...especially going that big. You can use files with less than 300 PPI.

    B.T.W. The pixel per inch number is really meaningless. It's used for how big an image will appear on a screen. You can change that number to 10000 or to 6...and it won't really change the image. If you 'resample' while you are changing it...then you will change the size of the image (in pixels) which is the important number to pay attention to.
     
  10. darich

    darich TPF Noob!

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    Agree with Harry and LWW - your camera doesn't have high enough resolution for 3foot images.
    I just upgraded to a 5D but i used a 20D for 18months. 8.2mp and better than most if not all compacts - i printed up to 30-20inches adn included a border so the image size was mabe 25inches maximum.
    Even with the 20D i wouldn't print at 36inches - the image would look pretty rough no matter how sharp the original is
     
  11. cap1957

    cap1957 TPF Noob!

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    I wasn't planning on using my Olympus camera to do the poster job. Should've made that clear. We were thinking that we would need a camera with about 600ppi to do that job, but where to find such a camera.

    Not sure what "interpolate" means.
     
  12. Big Mike

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

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    Interpolate is what we call it when you 'up-size' an image with software. Basically it means that the software has to make up pixels to make the image bigger. The more pixels it has to make up...the less the quality.

    Some software does this better than others. Photoshop is OK...Genuine Fractals is one of the best.

    For printing large images...the Mega Pixel count is important. So you will want the most you can get. Depending on the shot, digital noise may be an issue...and larger sensors (like in a DSLR) will give you less noise...and therefore make enlargements easier/better.

    There are other factors that go into making big prints. The quality of the lens for one. It's also important to maximize the sharpness of the image by using a tripod and remote release.
     

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