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  1. #1
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    Hello. What size in pixels should an image be to perfectly fit the background to slides? And what kind of images do not distort when re-sized in Powerpoint?
    Thanks, Andy.

  2. #2
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    The default size of a slide is 10" x 7.5". If you use a photograph as background it will probably be a .jpg file. PowerPoint uses the print size of the .jpg file which depends on the dpi setting, and which may be different from the screen display size of the .jpg file in other applications if the dpi setting is different from that used by Windows. So it becomes rather complicated.

    All bitmap-type pictures(.bmp, .png, .gif., .jpg) will show pixelation when enlarged. If you want to be able to enlarge a picture smoothly, it needs to be a vector graphic - see Vector graphics - Wikipedia, the free encyclopedia.

  3. #3
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    [quote name='HansV' post='770842' date='16-Apr-2009 16:20']The default size of a slide is 10" x 7.5". If you use a photograph as background it will probably be a .jpg file. PowerPoint uses the print size of the .jpg file which depends on the dpi setting, and which may be different from the screen displsay size of the .jpg file in other applications if the dpi setting is different from that used by Windows. So it becomes rather complicated.

    All bitmap-type pictures(.bmp, .png, .gif., .jpg) will show pixelation when enlarged. If you want to be able to enlarge a picture smoothly, it needs to be a vector graphic - see Vector graphics - Wikipedia, the free encyclopedia.[/quote]
    Thank you. It occurred to me that the image should be the same size as the screen resolution but, as you suggest, it's a little more complicated than this. Andy.

  4. #4
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    [quote name='andrewgibsonsw' post='771135' date='18-Apr-2009 10:02']Thank you. It occurred to me that the image should be the same size as the screen resolution but, as you suggest, it's a little more complicated than this. Andy.[/quote]
    Essentially, the image should be the same size as the screen resolution - if you are preparing the file for a screen show. This is more complicated than it might otherwise be because the screen resolution of your computer may not be the same as the resolution you get through the projector. Most modern projectors will push out an image of 1024x768 pixels so that might be a reasonable target. The ratio of width to height is most important if you don't want distortion - the general screen ratio should be 4:3 but you might have a widescreen projector with a different ratio.

    If you are preparing the image for a print then you may want to increase the resolution since a printer can show more detail than a screen. You don't need to push the resolution all the way to the dpi of the printer though - 150-200 pixels per inch is fine on a 600dpi printer. The actual resolution of the image will depend on the size you do the print. For instance if you are only printing handouts then the image is squashed into a smaller area and therefore the screen resolution is likely to be easily high enough.

    My own personal belief is that a background image on a PPT show should not be very high at all since you don't want people paying close attention to it. The words and graphics you put on the screen are the reason people are looking at the show and the background image should be subtle enough to not detract from your message. The lower the resolution of the image, the smaller the file size and the faster the show displays. If you test a small image and you don't notice any zoom or compression artifacts then nobody else should either.
    Andrew Lockton, Chrysalis Design, Melbourne Australia

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