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Imagine all possible colors as living within a 3D volume that has been mapped with a coordinate system that consists of no less than three coordinates. This coordinate sytem is color soace. The neat thing about color spaces is that information that is difficult to 'get at' in one color space can be easily acquired in the channels of another color space. A good example is the Lab space which neatly places all luminance in the L channel, leaving the color information in the a and b channel. This means that the color values of the image can be edited without affecting its luminance (and visa versa). This is slightly advanced territory and is not something that you are ever going to want to do often, however when you need it you are grateful for the fact that it is there.


Image Size

This scales up or down the document and it's contents. not to be confused with Canvas Size which changes the size of the canvas upon which you are working. Usually, the most convenient way to use this is via its Percent parameter.

If you un-tick Resample Image then all the values in the Pixel Dimensions component of the dialogue box become grayed out.

Newbies (and even pros) get very confused over the value Resolution. A high resolution is NOT a one stop shop guarantee of image quality, in fact on its own resolution means nothing (notice how PS takes no time at all to process a Resolution change). Consider the situation that you want to print a high quality postcard-size photo of someone:

- You have one image with a 'high' resolution of 300ppi. However, it is only one inch by two inches.
- You have another with a 'low' resolution of 70ppi. It is exactly what you want because it is one hundred inches by two hundred inches and therfore has far more pixels to play with.

Resolution is a function of printing or viewing size (inches) and the dimensions of the image as measured in pixels. The only important value is pixel dimensions, which is a good indicator of how much information the document can contain.

Canvas Size

This changes the size of the canvas upon which you are working. Not to be confused with Document Size which scales up or down the document and it's contents. Usually, the most convenient way to use this is via its Percent parameter. I stopped using Canvas Size so much since I discovered that it is possible to make a canvas larger as well as smaller using the Crop Tool.

Image Rotation

These commands will rotate the entire document. The one really useful value is the Flip Horizontal command. This flips 'mirror-wise' the document that you are working on. This fliperoo important. Why? Heres why:


Artists, since time imemorial, have looked at their work in the mirror to check on its composition. By doing so they are 'refreshing their view' and are more able to spot defects in its form and structure. A Flip Horizontal does the same thing. Pro painters have this hot-wired into a Action which has been tied to a keystroke (it has no natural keystroke command). For small files (such as those with a low layer count) this menu command is fine. For larger files it would be too slow to work.

For larger files an alternative to this menu command is the following set of keystrokes: Command A (select all), Command Shift C (copy all visible layers as merged), Command V (paste). This is most convenient to do when you are located in at the top of the layer stack so the pasted layer is not occluded by other layers. This new, flat version of your document can then be Flipped using a Free Transform. This can be followed up by making a new layer of top of this layer and painting roughly into it any drawing changes that you think your image needs. This notations layer can be flipped using the Free Transform (be sure to Command A first or it will be a local space transform and not register properly with your image.

May I be unequivocal for a bit? If you have not flipped your image several times in the course of the painting then you are not, nor will you ever be, capable of critically reflecting on your work. You will be condemned always to swim amongst the amateurs and forever be a loser.