Unit 11: Intro to Photoshop
Unit 12: Design Accessibility
Unit 13: Product Design Thinking
Unit 14: User Experience Design
Unit 16: Introduction to Design Portfolios
Unit 17: Portfolio Development
Unit 18: Personal Branding
Unit 19: Case Studies
Unit 20: Portfolio Website Design
Unit 21: Career Coaching
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Understanding Pixels and Resolution

Photoshop is a Raster-based program

What is Raster?

Before we dig into more exercises, it’s important to understand that Photoshop is a raster-based program. This means that all the images we see in photoshop are made up of pixels. This is different from Illustrator, which is a vector-based program.

Remember, vector graphics are mathematically created computer graphics that are infinitely scalable. Raster-based graphics and images are not infinitely scalable because they are made up of a set number of dots or pixels. This is called an image’s resolution.

DPI vs. PPI

The word we use to understand how big a raster-based image is its resolution. The resolution is essentially how many pixels or dots per inch an image is made up of. This concept originated in print, photography, and designing for print. The term “DPI” meaning ‘dots per inch’. This refers to how many individual dots of ink per inch a printed image will have. This is called print resolution.

In the digital age and on screens, this translates to “PPI” or ‘pixels per inch’. This is called screen resolution.

Setting Resolution

The number of pixels per inch in our file needs to be determined before we begin designing, because we cannot add more pixels (in otherwords, increase the resolution) after the fact without degrading the overall quality of the image.

You are most likely familiar with the term “pixelated”. The pixelated look occurs when we try to force an image to be larger than the initial pixels per inch that it is made up of. This is because the computer program tries to guess the color of the pixels being added—this isn’t information the computer already has. Usually, the computer cannot perfectly predict the colors of the added pixels, and this is where fuzziness and image distortion becomes visually apparent.

In order to avoid a pixelated result, you must always set the resolution of your new photoshop files when you first create them and check the resolution of all photos or images you bring into photoshop to make sure you know its true size.

Best Practices

The gold standard for anything being printed is 300 DPI. Anything printed with a resolution below 300 will typically begin to look low-quality.

For digital work that will only ever live on screen, 72PPI used to be standard. It’s important to note that screen resolutions have increased dramatically over the years, and it is now a good idea to increase your digital work PPI to around 100-150PPI to avoid low-quality, or pixelated, displays.

Sizing vocabulary to know

Image Size

How many bytes the image file takes up on a computer.

Image Dimension

The dimensions of an image are the physical width and height. For example, the cow image below is 3488px by 2616px. In inches that would be 11.6in by 8.7in.

Screen Resolution

The pixel-density of an image that is meant to be viewed on a screen.

Print Resolution

The dot-density of an image that is meant to be printed.

DPI

Dots per inch. How many dots per square inch in an image meant to be printed.

PPI

Pixels per inch. How many pixels per square inch in an image meant to be viewed on a screen.

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