From the Image Drop down list you have 3 options:
- Image> Rotate> Rotate Clockwise 90 degrees [Rotate right]
- Image> Rotate> Rotate Counter Clockwise 90 degrees [Rotate Left]
Whole image rotates 90 degrees in any direction.
These two options can also be accessed from the main toolbar.
This provides a lossless way of rotating images. [no pixel damage]
If you rotate a background layer or "all layers" of an image containing a background layer, the canvas will enlarge to accommodate the rotation. [ the extra "space" is filled with whatever you have in your background materials palette]
With raster layers, you will always get a little blurring [degradation] of your image, with the rotation and this is multiplied each time you repeat a rotation. Therefore, if you find that your rotation is not quite as desired it is always better to undo and repeat with a different degree setting, rather than try to make adjustments. Then apply a little sharpening.
Vector layers will remain sharp with this sort of rotation.
Pick Tool [Deform, Object Selector]
Of course you can always use the Pick Tool [Deform, Object selector] for this sort of rotation [at least of a single layer] but never with the same degree of accuracy unless you actually put in values in the toolbar. If you try to rotate a background layer, it will be promoted to a raster layer but the canvas will NOT be enlarged automatically to accommodate it.
The straightening tool.
This works in a similar manner to the free rotate, except that you use a guide to set your angle or set it in the toolbar. You can also save presets.
If you "untick" crop image when you straighten a background the canvas will enlarge in a similar way….using your background materials palette to fill the "space". If the straighten tool is used on a raster layer, the image will be rotated about its centre, not the centre of the canvas. If degree angles are used, the degree of rotation is to the left :)
I often use the Free rotate option when creating animations.
If I require a series of different rotations, I always make copies the original layer and then apply the degree of rotation to each copy. This maintains the clarity of the image. This isn't necessary if I am using vectors.
It really helps to use a quick script...or if you create the same sort of image often, save a script. [ e.g. a sweeping clock hand]