psd A .psd extension file is an image file created with the help of Adobe Photoshop. PSD is the default extension used for saving a Photoshop Image which can have either a single or multiple layers which can be worked individually even after having saved the file. The file can also be saved in other formats like .jpg, .tiff, .gif or other imaging formats but if a user wants to edit the individual layers later, it is necessary to save the .psd file without overwriting it while converting it to another format. Converting a .psd extension file into an image file in another format flattens the image so that it can be viewed as a regular image. The images created using this extension are of a very high resolution and the quality in terms of clarity is extremely good as compared to other commonly used image formats like .jpg, .png or .bmp.
sgi A .sgi extension file saves images in the original Silicon Graphics Image format. These files are originated from the library of SGI images that were there on every Silicon Graphics machine. SGI files are also referred to as RGB, IRIS or Irix RGB., .sgi image files can be saved in 8-bit color, 16-bit or 32-bit color. GIMP has the compatibility to read and write .sgi extension files and also has a dialog box that pops up to help select the compression type. The preferred compression is RLE and while it reduces the file size, it is advisable to check once it is done to ensure that the file size is indeed reduced as sometimes the size is more than the actual file size.