Understand raster and vector files

Photoshop supports two types of images: raster and vector. Raster images use pixels, while vector images use scalable shapes.

Raster images

Raster images use a grid of tiny squares called pixels. Each pixel stores a color.

When you edit raster images, you modify individual pixels.

Resolution dependence

Raster images have a fixed number of pixels.

• Enlarging adds new pixels and can cause blur or pixelation.
• Reducing removes pixels and removes detail.

Plan your image size to avoid quality loss.

File size considerations

Raster images store color data for every pixel, which increases file size.

Compression reduces file size:

• JPEG (lossy): Removes some image data.
• PNG (lossless): Preserves all image data.

Choose a format based on quality and file size needs.

Common raster formats

Photoshop works with several raster file formats, each suited to different purposes:

• JPEG: Supports a wide range of colors; ideal for web images.
• PNG: Supports transparency with no quality loss.
• TIFF: Used for print and archiving.
• GIF: Supports simple graphics and animation.
• PSD: Photoshop’s native format with layers.

Vector images

Vector images use shapes, lines, and curves instead of pixels. Mathematical definitions keep them sharp at any size.

They are used for logos, icons, text, and illustrations.

Resolution independence

Vector images do not rely on pixels.

You can scale them to any size without losing quality. This makes them ideal for designs used across multiple sizes and formats.

File size advantages

Vector files are smaller than raster files for simple graphics.

However, complex vector artwork can increase file size. Converting photos to vector formats can create large files.

Common vector formats

While Adobe Illustrator specializes in vector creation, Photoshop can work with these vector formats:

• AI: Adobe Illustrator format.
• EPS: Print-ready vector format.
• SVG: Web-friendly vector format.
• PDF: Supports both vector and raster content.

Working with both types in Photoshop

Photoshop creates raster images by default. You edit pixels when you paint, retouch, or apply filters.

You can also add vector elements:

• Use shape tools to create scalable vector layers.
• Use type layers to keep text sharp.

These elements work together in a single document.

Quality considerations for combined artwork

Combining vector and raster content affects output quality.

Transparency and flattening

Photoshop flattens artwork with transparency when printing or exporting.

Flattening merges layers into a single image.

Image resolution

Image resolution measures how many pixels fit into 1 inch. This value is called pixels per inch (PPI).

• Low PPI → pixelated images.
• High PPI → larger files with no visible benefit beyond limits.

Guidelines:

• Screen: 72–96 PPI.
• Desktop print: 150–300 PPI.
• Professional print: 300 PPI.

Printer resolution and screen frequency

• PPI (pixels per inch): Image resolution.
• DPI (dots per inch): Printer resolution.
• LPI (lines per inch): Print screen detail.

Use appropriate resolution settings based on your output.