Choose the Image Size command.
Check Resample.
Change the resample method to Bicubic Smoother, since we are increasing the pixel dimensions.
Type 12 in the Width field for document size and observe the following: Resolution remains at 266.667, but the pixel width and height double to 3200 by 2400. Also notice the file size readout. It should say 22M (was 5.49M). The file size quadruples as we double the pixel dimensions!
Click OK now and let's see what happens to our image. By going to View > Print Size we can see it's approximately 12 by 9 inches on screen.
Now set the magnification to 100% and look at some of the areas where there was a lot of detail in the original, such as around the petals in the main flower. You'll notice these areas will be a bit blurrier than the original. That's because resampling results in a loss of quality — especially resampling to increase the pixel dimensions — so you should avoid it whenever possible.
