Image Resolution and Pixels Per Inch {ppi}

RESAMPLING:
Also called interpolation (page 57 in your text)
In computer graphics interpolation means Photoshop's interpretation of what something should look like, when it does not have sufficient data to carry out your request. Interpolation is an averaging process. When you resize an image up or down or increase the resolution up or down, Photoshop searches for data to help support the application's decision on how the resized image will look.

One of the tasks that you will need to perform frequently is the scaling or cropping of images. The command for changing the image size is Image>Image Size. The dialogue box displays the width and height of your work area, and you can change its dimensions by entering new values (make sure the units are set to pixels). To the right, you'll see a chain icon that indicates which perameters are linked, depending on whether you have selected Constrain Proportions and/or Resample Image at the bottom of the dialogue box.

Constrain proportions ensures that if the width is changed, the height changes accordingly (and vice versa). Unless you plan on intentionally distorting the image, perhaps as a special effect, this option should always be checked. The Resample Image option ensures that Photoshop resamples the image if you make any changes in its resolution. See your text (page 55, 57) for more information on resampling (interpolation).

The Image Size dialogue box also displays a value for resolution. Ideally this value should be set to the screen resolution of 72 dpi, but this is more or less a cosmetic task. To a browser or HTML authoring program, it makes no difference whether the resolution of an image is set to 72, 120, or 300 dpi. To the browser a pixel is a pixel - it will always display the real size of the image. I mention this because it is different from desktop publishing. Resolution for print is different.

If you are printing your digital photographs you will see the difference in quality. Printed images with 72 dpi are typically blurry, or pixelated. Colors in low resolution graphics can also band, meaning the gradations of color are blocky or chunky. Higher resolution graphics (over 120 dpi) will print much better. The printer you use can also determine what resolution is necessary. For example oversized printers (used for printing poster sized images) can sometimes require a minimum dpi for optimum prints.

Most often you will want to downsample, but in demonstrating upsampling in my video lesson, you will be able to understand both concepts. You should understand the difference between downsampling and upsampling after completing this lesson.

One of the upsampling softwares is called Genuine Fractals. For more information about this go to:

http://www.ononesoftware.com/detail.php?prodLine_id=2

PART 1:
Using the tutorial "Resizing an Image" from your text (Lesson 2 page 55) downsample one image. Use the 'CW with clipboard.jpg' image from the text support files.

Write onebrief paragraph about your findings in downsampling.

PART 2:
From the tutorials you completed (One on One text) on making selections and the video tutorial on using the Quick Selection Tool, write one paragraph about your findings when working with the various selection tools reviewed in this lesson.

Please send both paragraphs via email text (you do not need to send me the graphics from the assigned tutorials.)

In the subject field of the email put your last name and first initial with the number of the homework.

Example: McIntosh J-HW2
Please use this format for each assignment that you email me throughout the semester.