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Image Size and PPI: the true answers

Discussion in 'Retouching and Post Processing' started by Electromen, Aug 7, 2008.

  1. The information below pertains to all versions of Photoshop and Elements.

    I'm reading the owners manual (User's Guide) for Photoshop CS3, I started on page one.
    A few quotes from the User's Guide (some are paraphrased by me to simplify them)

    Image Size and Resolution

    The pixel dimensions (image size or height and width) of a bitmap, or photo is a measure of the number of pixels along an image's width and height. Resolution is the fineness of detail and is measured in pixels per inch (PPI) The more PPI the greater the resolution.
    The combination of pixels and resolution (PPI) determine the amount of image data. Unless and image is Resampled, the amount of image data remains the same as you change either pixel dimension of resolution (PPI) and vice versa.

    In the Image Size Dialog box, Turn off Resample Image.

    Deselect Resample Image, because you don't won't to change the amount of image data in your photo. Change the width or height or the resolution. As you change tone value, the other two values change accordingly.
    End Quotes from User's Guide
    Try it, turn off Resample Image. I think all of our previous questions about PPI and Image Size will be answered when you try it. Try changing Image Size, then try changing PPI.

    Using the Crop tool
    To crop without resampling, leave the PPI box empty.
    To resample during crop enter values for width, height and PPI

    Here are a few more quotes FYI

    Bitmap images - technically called raster images - use a rectangular grid of picture elements (pixels) to represent images. Digital photographs are bitmaps because they represent subtle gradations of shades and color. Bitmaps are resolution dependent, they contain a fixed number of pixels. They can lose detail and appear jagged if they are scaled too large or printed at a lower resolution.

    Vector graphics are made up of lines and curves. they maintain crisp edges when resized. Vector graphics are best for artwork and logos. Add Vector graphics to Bitmap images at the Bitmap's final or cropped resolution.

    I bought the owners manuals for the entire Adobe CS3 Creative Suite for $24.95 Any owners manual can be purchased from Adobe. The one for PS alone is 823 pages.
    Last edited by a moderator: Aug 7, 2008
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