Adobe Photoshop : File size and resolution

It is often the case that when working in Photoshop you are working on a high resolution copy of the original and when it is complete you make lower resolutions to email clients or post on the web. Save for Web & Devices is a really handy tool to use in this situation. It is also a really handy tool to use when you are trying to learn about file size, image size and resolution.

Go to File/ Save for Web & Devices...

This window appears and can show up to 4 different versions of the same file using the 4-Up tab.

From this window you can make changes to the original and save it as a new file. Save for Web does not change the original image. All changes are made to a new file that you name and choose where it will be saved. From this window you can reduce the number of pixels (you never want to increase more than the original), test different qualities of jpeg and compare jpegs to gifs. This is a great feature and it will become your friend.

Practice saving a file using this feature. How small can you get it before it is of unacceptable quality? What seems to work better, gif or jpeg? Notice the difference between these two file types. Does it make sense that gifs are better for high contrast images and jpegs are better for smooth dithering?