Quite often, a shot you take may look cramped in the frame, either due to space restrictions at the location, or the lens type used.
One way to improve composition is to add canvas to the original picture and place the subject in an optimal position - usually on a third.
Here's how to place a thirds grid on your original shot to check composition. I'm using Photoshop CS4, but most versions of Photoshop will support this.
Go to Edit>Preferences>Guides, grids, slices and counts and in the Grid section enter 33.333 in the Gridline every text field and select percent from the measurment dropdown. Enter 1 in Subdivisions.
Then, with your original open, turn on the grid View>Show>Grid (Control + ' on a PC) and the thirds grid will overlay on your shot, allowing you to judge if you need to add canvas space to place the subject in a better position. As an example in the illustration below, the girl's head is too high in the shot, and the composition looks cramped. (left) Ideally, you would have the girls eye area in a third, and have her off centre, on a vertical third. In this case, adding space, (right) provides a better overall composition.
You can add canvas size laboriously by using the Image>Canvas size dialogue box, but the fastest method is to select the Crop tool. Ensure it is not set to a preset crop (8X10 for example)> If it is, right click the tool and select reset tool. Then use the tool to select around your image, while leaving the grid in place. The crop tool will now have "handles" mid way along each side which allow you to drag the canvas out to wherever your original shot looks better composed. Press enter. The added space will be white or black depending on your foreground and background colour.
You now have some options depending on your shot. If it's a simple background, such as plain white or black, or a nature shot with a blurred background, you can easily clone the existing background in. Or you can use the Rectangular marquee tool to select some of the existing edge, or top/bottom. Then copy & paste and use the Move tool to place the pasted section into the new canvas.
You will need to use some cloning to ensure you don't see an edge at the transition, or to clone out any obvious duplicated parts. If you have CS4, you can use the Marquee tool to select an area, then edit, content aware and use this to drag the selected area to stretch it into the new canvas. This can be a hit and miss proposition, as you may also need to perform some creative cloning. If the background is complex, you may have to spend quite a lot of time at this technique.
Article by Willie Baneham
, illustration Brian 1208.