Graphics Programs Reference
In-Depth Information
If you are planning to print an image and you want it to look great, then make sure its
resolution is 300 ppi. When printed on paper, the image will contain 300 dots per inch
(dpi), which is enough resolution to print a fine-looking image. (This topic uses images
at 300 dpi.) For images projected on a screen, however, 300 ppi is not necessary. You
will not be able to see the difference on-screen between a good 100 ppi image and the
same image at 300 ppi. Most projection systems will not display an increase in quality
over 100 ppi.
While you can use images with 300 ppi or higher in presentations, there is no advantage
to doing so. A 300 ppi image contains a lot more data than the same photo at 100 ppi
and the file size is much larger. If you use many images with unnecessarily large files, the
presentation file itself will become quite large. Depending on your hardware and
software, this could lead to an unstable file that freezes or runs slowly. Even on newer
computers it will take longer to save changes to the presentation—something you do
often while you work—when your files are larger.
For a long time, the standard recommended resolution for images intended for display
(not print) was 72 ppi or 96 ppi for PowerPoint on Windows machines. Many
presentation professionals recommend using 100 ppi images in slideware as the color
may look a little better. But performance matters too, so keep the file size of images as
small as possible while still keeping the dimensions large and the quality high. As a
general rule, use images that are 72 ppi to 100 ppi with dimensions that are the same or
very close to the slide dimensions (for example, 800 x 600 or 1024 x 768) when you
want to use an image that fills your entire slide.
Improve images through cropping
Cropping is a technique for reframing or adjusting the composition of an original
photograph. Of course, it's always better to take the perfect shot or purchase the perfect
image, but that does not always happen. Cropping changes the image to better suit your
needs. For example, you may have images of interesting subjects, but the composition
is not what you had hoped. I have loads of holiday snapshots that are not that great, but
can be improved with a bit of cropping.
I took this shot of Bondi Beach in Australia last winter (July) using a simple digital point-
and-shoot camera. The original resolution was 300 ppi, measuring 2816 x 2112 pixels.
The size of the file was 4.2 MB. For images that will be placed in slideware, a resolution
of 72 ppi or 96 ppi is usually fine. So I first reduced the resolution to 72 ppi, which
decreased the file size to 1.9 MB. Next, I decreased the dimensions of the slide to
something closer to 1024 x 768, the size of my slides, using basic photo-editing
software. Since I started with such a large image, however, I can go inside the
photograph and frame it in a way that is a little more interesting and specific. Using the
cropping tool, I selected an area of the photograph that shows only the surfer, leaving
plenty of empty space in case I want to place text inside the image. Now, the image
measures just a bit over 1024 x 768 and the JPEG file size is about 300 KB. I could
reduce the file size further through more compression, but this would decrease the
