Some Notes on Sizing Images: Part 4, Meeting an Image Editor

Now that we know something about the resolution and image size trade-off, let's see how you'd actually change the image settings. Take a look at this screen shot from Photoshop Elements:


The top section shows you the current dimensions of the image in pixels, at you can also see that the image has 32.7 megapixels. The latter isn't necessarily the same as the file size, depending on the type of image file. A JPEG file will be compressed and, so, smaller than, say, a TIFF image file. Although you see the width and height in pixels, you can choose other forms of measurement, like inches. However, pixels is a useful choice because you can relate it to the properties of the file - X pixels across and Y pixels high.

Next section is called Document Size. This is how the image will display, and you can see both the dimensions and resolution. You can change the units here (even choose a percentage unit if you want to scale the image up or down a given amount).

In both the Document Size and Pixel Dimension sections, the a bracket with a chain connect the width and height figures. That keeps the dimensions in a constant ratio. If you wanted to change the two disproportionately (not done that often in photography, unless you're trying to distort the results), you can click on the chain and it will appear broken, telling you that the two are no longer linked.

You can also change any of the numbers and all of the others will change accordingly, so long as the Constrain Proportions box at the bottom is checked.

Tomorrow we'll actually manipulate the image size.