Here's our picture open in Photoshop Elements. This is version 4 running on a Mac so it may look a little different if you're on a PC but the commands are all the same. If you're running “full” Photoshop then the screen will look different again but I'll outline any differences as we go.
From the image menu, select resize and then image size. You can shortcut this by just hitting Ctrl-Alt-I (Cmd-Opt-I on a Mac). On full Photoshop you select image size directly from the image menu but the keyboard shortcut is the same.
You will get this dialogue. I've enlarged the central panel to make it easier to read.
Here I have just typed 600 for the width. Since “constrain proportions” is checked the height is automatically calculated for me. Make sure that “resample image” is also checked or it won't let you change the pixel dimensions. There's a drop down next to this that lets you choose the resample method. Strictly speaking, bicubic sharper usually give the best results when reducing the size of a picture for the web but it is very similar to bicubic which we have used here.
Hit OK to resize the picture and then it's time to save it.
From the file menu select save for web (Ctrl-Alt-Shift-S / Cmd-Opt-Shift-S) to get this dialogue (this is identical for Elements and Photoshop).
The dialogue shows your image twice. On the left is the original, on the right is the version compressed according to the options you set in the panel. In full Photoshop you have various other view options as well. Here's the panel.
I selected jpeg format and then “high” quality. The preview shows me how this will look and also the file size at this compression ratio. If the quality looks bad then move the slider to the right. If the file is too big then move it to the left.
When you're happy, hit “OK” and enter a file name to save it. Then you will be taken back to your image. Close it without saving - if you allow Photoshop to save it then it will save the resized version and you will lose your original.
Sharp eyed readers may have noticed the “new size” box in the save for web dialogue. It's true that you can resize and save for web in one go. Just enter the new size (e.g. 600 for the width) and hit apply. Then save for web as before. This looks like a good one step solution but I don't recommend it. Save for web was only designed to cope with web sized images. If you save for web a full resolution file you may get the following warning:
On my Mac with 4.5 GB of memory I know it's OK to proceed but on a low spec PC this could cause a long wait or a system crash. I find it's better to do it in two steps.
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