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kodos1
USA
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 Posted - 03/04/2008 : 16:15:53
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Hi,
I'm creating a slide show in powerpoint for projecting onto a screen. Do I need to save the photos in a higher resolution than 72? What is best dpi for this? Will they look bitmapped on the screen if I don't?
thanks in advance. |
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lrcrabtree
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Posted - 03/04/2008 : 20:19:04
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Welcome to the PowerPoint presenters forum!
All screens display images in resolutions up to but no more than 72dpi. Displaying images on screen in resolutions higher than 72dpi does several things.
1. Increases the file size of each image.
2. Increases the overall size of your PowerPoint presentation making it slower to load and open.
A previous thread which might prove of great interest desAlp is Compress powerpoint presentation where issues such as image size, format, etc. are discussed.
When an image is resized, the size of the image, ie. its width and height are resized on screen. If the image was in its original state very small and you are scaling the image to be full screen than naturally you can expect a large degree of pixelation. This would occur even if your image was several hundred dpi such as 300dpi. That is because onscreen, dpi represents the amount of data and information per single pixel. Naturally the more amount of information that you have per pixel the better. However, once you get over 72dpi the amount of data that can be displayed on screen is no more and so interpolation occurs (this is when an image appears to pixelate or become fuzzy etc).
This interpolation will appear much worse if the image was saved in a lossy format for example JPG at lower resolution settings.
Ultimately desAlp, PowerPoint is extremely good at scaling and resizing images for presentations. However if you provide it with extremely poor images and it is expected to scale them to full screen you can expect the results to be poor. Choose your images carefully. Never allow them to be more than 72dpi but do allow them to be large so that you can scale them down rather than up.
If you are using JPG's try to save them in higher levels of compression rather than lower levels. And if you are having many images in your presentation be aware of file size, most specially if it is also your intention to distribute your PowerPoint presentation via email.
Charles Henry
Creative Director, 123PPT
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preparing photos for powerpoint slide show
