What are Pixels and Resolution? - Colorado State University

PDI 2009 Working with Images for PowerPoint to get the Best Result

What are Pixels and Resolution?

Image Resolution: Image Resolution is the number of pixels displayed per unit of printed length A measurement used in printing.

Pixel: The smallest element of any picture.

From Photoshop, open a file, zoom in, draw a marquee around any part of the image. Notice the image is made up of blocks of color pixels.

Pixel Dimension:

Pixel dimension is how many pixels make up the image. How many pixels wide by high. Example: 1024x768 pixels

Onscreen Images: Resolution is measured in PPI pixels per inch a measurement of how many pixels are

going to be displayed per inch.

Images for Print: Resolution is measured in DPI dots per inch printers print dots

Caution: Don't use these terms interchangeably

Resolution Measurement is really how to tell the printer how tightly to pack the pixels together during printing process.

If you increase an image resolution, pixels are packed more tightly, higher quality print If you decrease an image resolution, pixels are packed more loosely, larger print, but

lower quality

Resolution can always be changed. Quality will vary.

For example, when downloading images from your digital camera, resolutions are going to be set at 72 ppi by default. If you want to print the image, you will need to increase the resolution and lower the size of the image.

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 1

Tip: On screen, our eyes cannot tell the difference between an image that is 72 ppi and 300 ppi. On a printer, the printer prints dots so it is visible when printing at an incorrect resolution.

Tip: Online images do not need to be more than 72 -96 ppi.

How much resolution do you need for a nice print?

Depends on the printer.

DPI for inkjets 200-300 for a photo DPI for ProPrinter (service) 300 + for magazines, brochures, books (call and ask) DPI for laser printer/newspaper 150-200 for newspaper ads, documents, newsletters

Tip: Images are made up of tiny dots called pixels.

Tip: Resolution is a measurement in printing and it matters only when you print. (DPI)

Tip: Resolution can be changed. Tip: Onscreen images it's the pixel dimensions that matter (PPI)

What image file format should I use?

File formats are important and each will have their own strengths and uses.

Jpg Gif Png Tiff psd If you take an image and save it using the different file types above, each image will be a different file size and have different levels of quality.

JPG File Type JPG's are most common. Great for photograph's. Good color scale Lossy type file you will lose quality every time you save the image The file size can be smaller

GIF Great for line art, animation Works best for solid blocks of colors (like cartoon type art)

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 2

 Lossy file format file size will be smaller, quality isn't as great

What File Types support Transparency?

There will be a project when an image will need to have a transparent background. Meaning, no background behind the image, no white box behind the image. This type of image can be placed on any background color.

Gif and PNG support transparent backgrounds

PNG file type Relatively New file format It is lossless, you will not lose quality when you save image A bit larger in file size Web browsers IE6 and below don't know how to display PNG with a transparent background. IE7 supports png's fine.

TIF file type Lossless format, you will not lose quality when you save image Don't lose pixels High quality file format Great for print File size is large Good for scanning/archive type

PSD file formats ? Photoshop file types Can print straight from PSD No compression on image so it is high quality Maintains all layers/good for editing

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 3

How do I resize an image for Print

Digital Camera file sizes will vary. All digital images will display as a 72 ppi for the resolution when opened in a photo editor. The size of the image will most likely be huge in dimension; too large for normal size printers. Let's resize and image for Print.

From Photoshop: File, Open and select the file: duck-key9.jpg

From the Image menu, select Image Size

The Size of image is 2.50M

Note the Pixel dimensions

Resolution is at 72. (Default when you open digital images.)

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 4

Changing the Resolution Without Changing Pixel Data: From the Image Size dialog box, deselect Resample Image Result pixel data is grayed out, pixel data is locked, which means your quality is locked. File size will not decrease.

Change the resolution to 300. Notice the document resized and the pixel data did not change. Tip: Your eyes are not going to see the difference between 72 and 300 on the screen. Notice the file size did not change.

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 5

Change the resolution to 200

The image resized File size is still the same

You can print the image from Photoshop or save it as a Tiff and print it later.

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 6

How do I resize and image for the Web or eMail?

From Photoshop open the file: Select Image, Image Size

Notice the size of the image. 2.5 M is kind of large for an email or a web page.

Leave Resample checked or turned on.

We do want to affect the pixels and reduce them in order to reduce our file size.

Email: 320 x 240 pixels is a good size for an image over email

Position the cursor in the Pixel dimensions area of the Image Size dialog box and change the width to 320 pixels. The height will adjust accordingly.

Press Ok.

Notice the image is smaller. Change the zoom level to 100% by

clicking twice on the zoom tool.

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 7

Save the File

Choose File, Save for Web File Format: jpg for photo Quality: choose High for email quality Press Ok and Save. Tip: size guidelines for email and web

C:\Users\fcampana.MORGAN\Desktop\How Come My PowerPoint Slides Take So Long To Load_instr.docx Colorado State University Computer Applications Training ?

Page 8

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download