Image file formats
Digital image file formats are important to understand. There are three kinds, classified by their position in the production process:
-
- Camera capture formats, such as Camera Raw (non-lossy) or JPG (lossy)
- Working formats, like Photoshop’s .psd or Gimp’s .xcf — These can’t be opened in any other application
- Interchangeable formats
- Formats for web – .gif, .jpg, .png, .heic, Google’s webp (These are compressible, or “lossy”)
- Lossless formats for printing — pdf and .tiff
This is a simplified overview of the most significant formats, attributes and uses.
Name | Channels | Mode | Color depth | Suffix | Pro / Con | Typical Use |
Raw (camera capture / input) | 3 | Raw |
12 or 14 bits per channel (4096-16384 shades) | Depends on camera type. EX: .crw (Canon) | Lossless Retains full gamut before formatting |
Storage in camera NOT FOR WEB |
GIMP Experimental computing facility | 4 | (any) | Working format (for GIMP) |
.xcf | Lossless | NOT FOR WEB |
Photoshop Document | 4 | (any) | Working format (for Adobe Photoshop) |
.psd | Non-lossy. No compression. | NOT FOR WEB |
Adobe Portable Document Format | N/A | File exchange. format | Non-lossy, can be compressed | OK for WEB Flat text, graphics, interactive elements, rich media | ||
Graphic Image Format |
1 | Indexed, greyscale | 8 bit, only 256 total colors but pallets vary |
.gif | no compression, good transparency, animation | FOR WEB – Maps, cartoons |
Joint Photographic Experts Group |
3 | RGB | 16 million colors (no transparency) |
.jpg .jpeg |
Good compression | FOR WEB – Complex photos. Best for simple web sites. |
Scalable Vector Graphics | 3 | RGB | 16 million colors |
.svg |
Scalable without aliasing / Not bitmapped | FOR WEB |
Portable Network Graphics |
4 | RGB | 16 million colors plus alpha channel (transparencies). | .png | Better compression than jpg, Best for https | FOR WEB |
High Efficiency Image Container | RGB | 16 bit processing, billions of colors | .heic | default format for Apple devices / from MPEG | FOR WEB (no transparency) | |
Tagged Image File Format | CMYK | 4 billion possible colors | .pict .tiff | Lossless Limited compression | FOR PRINTING | |
Flexible image transport system | 4 | (any) | Scientific and archival format | .fts, .fits | Non-lossy; backwards compatible (to 1981). Good photometric notations | Working format for FITS Liberator NOT FOR WEB |
More
- Adobe info on Color Modes
- Image formats (Wikipedia list)