File n Picture Format's..

PSD

* You will want to save as a Photoshop PSD when you have many layers that you want to preserve.
* Saving this way will retain adjustment layers, your masks, shapes, clipping paths, layer styles, blending modes.
* Useful if you need to maintain transparency.
* The downsides to PSDs the large size and the compatibility.
* Only those with Photoshop will be able to view them, and you will need to save another way for printing.
* You cannot share on the web as a PSD.

TIFF

* This targeted file format is the highest quality and is excellent for print as there is no loss in quality
* Retains information in layers, depending how you save it.
* The downsides are the extremely large file size and you cannot display on the web in this format.
* Lossless format so you will retain information from your images as you re-open and re-save.

JPEG

* The Joint Photographic Experts Group format is the most common type. It is viewable by all and can be used for print and the web.
* When saving as a jpg, you decide what quality you desire from a 1-12.
* The biggest downsize is that the jpeg format is lossy. Each time you open and save, the image compresses and you lose a small amount of information.
* Another downside is that layers are flattened upon saving so you lose the ability to go back to past edits to tweak.

GIF

* The Graphics Interchange Format is great for web graphics with animation.
* The file size is very small so these files load fast on the web.
* The downsides are limited colors and does not handle photographs well. No recommended for print work.
* Lossless format so you will retain information from your images as you re-open and re-save.

PNG

* The Portable Network Graphics format also creates smaller file size but without the quality loss of a GIF.
* Often used for graphics instead of GIF.
* Lossless format so you will retain information from your images as you re-open and re-save.
* You can share on the web.