Page 17 - CC2018_WD_Look_Inside

5. Choose Image>Image Size.
The Image Size dialog box shows the number of pixels in the image, as well as the image
dimensions and current resolution. You can change any value in this dialog box, but you
should understand what those changes mean before you do so. Note:
As you can see, this image is currently 37.5 inches wide and 50 inches high, but it Press Command-
was photographed at 72 pixels/inch. For most commercial printing, you need at least Option-I/Control-Alt-I
300 ppi. You can use the principle of effective resolution to change the file to a high to open the Image Size
enough resolution for printing. dialog box.

Click and drag in the The actual number of
preview window to pixels in the image is
show a different area. the most important
information.
Use this widget to
change the preview
percentage.

6. Check the Resample option at the bottom of the dialog box (if necessary).
The options in this dialog box remember the last-used choices. The Resample option
might already be checked in your dialog box.
Resampling means maintaining the existing resolution in the new image dimensions;
in other words, you are either adding or deleting pixels to the existing image. When this
option is turned on, you can change the dimensions of an image without affecting the
resolution, or you can change the resolution of an image (useful for removing excess
resolution or downsampling) without affecting the image size.

7. Change the Resolution field to 300 pixels/inch.
When you change the resolution with resampling turned on, you do not change the file’s
physical size. To achieve 300 ppi resolution at the new size, Photoshop needs to add a
huge number of pixels to the image. You can see at the top of the dialog box that this
change would increase the total number of pixels from 2700 1 3600 to 11250 1 15000.
You can also see that changing the resolution of an image without affecting its physical
dimensions would have a significant impact on the file size. Changing the resolution to
300 ppi at the current size would increase the file size to nearly 483 megabytes.

When Resample is
checked, changing the
Resolution value adds
or removes pixels.

Higher resolution means larger file sizes, which translates to longer processing time
for printing or longer download time over the Internet. When you scale an image to
a smaller size, simply resizing can produce files with far greater effective resolution
than you need. Resampling allows you to reduce physical size without increasing the
resolution, resulting in a smaller file size.

The caveat is that once you discard (delete) pixels, they are gone. If you later try to re-
enlarge the smaller image, you will not achieve the same quality as the original (before
it was reduced). You should save reduced images as copies instead of overwriting the
originals.

Project 1: Composite Movie Ad 27