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Basic Edits: Cropping and Rotating
This section covers two of the most basic and important image manipulations that you can apply. Everyone should understand how to do all of these.
Cropping
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Cropping is removing some of the image from one or more of the sides. Possible reasons you might want to do this are:
- to create a more pleasing picture / improve composition.
- to enlarge certain parts of the image (if you crop an image and then view/print what’s left at the same size, you are in effect enlarging the remaining part of the image).
- to change the aspect ratio.
- to create an image of a precise pixel size (e.g. 400 x 300 pixels)
To crop an image, first select the crop tool (third tool down on the left in the picture showing the Photoshop toolbar). If you want to crop your image to an arbitrary rectangle and aren’t bothered about the aspect ratio, make sure the width, height and resolution boxes on the options toolbar are all blank, and then just drag a rectangle over your image. The area that is going to be cropped off (i.e. removed) is shown in dark outside of your selected rectangle.
If you want to crop an image for printing at a specific size, enter the dimensions in the width and height box (ensuring you put either ‘in’ for inches or ‘cm’ for centimetres after the numbers) but make sure the resolution box is blank. When you now drag over the image to mark your crop area, the rectangle will be constrained to the aspect ratio of the dimensions you entered. By leaving the resolution box blank Photoshop will not resize the image (therefore you maintain the image quality) however it will set the resolution embedded in the image file to the correct PPI value.
If you want your image to be a precise number of pixels in size, enter these two values into the dimension boxes with ‘px’ after the numbers. When you drag your crop box over the image, you will again be constrained to the aspect ration of the specified dimensions, however when you click to confirm the crop, the image will be resized to the exact pixel resolution specified.
You can move and resize the crop area before committing to it. When you are happy, click the check/tick button on the options toolbar or cancel to revert back to the full image. |
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Photoshop crop tool in action
Crop and Sraighten in One Operation
The same crop tool mentioned in the previous section can also be used to straighten an image that’s slightly wonky. It is incredibly useful that Photoshop has combined these two features into one tool as straightening an image usually involves cropping a small amount from round the edges anyway.
If you move the cursor to just outside one of the corner handles, the cursor will change to a double pointed curved arrow. You can now rotate your selected area to align one of the edges with something you know should be perfectly horizontal or vertical in the image. When you confirm the crop, it will rotate the image by the amount you rotated the crop region.
Crop and image straightening carried out in one operation. Note that I had to specifically go out and take a wonky photo to illustrate this! Honest!
Rotating (90°)
This section covers rotation by 90° (clockwise or anticlockwise) and 180°. Rotation by small amounts to straighten an image was covered in the previous section.
Image rotation should be very simple but it is actually a source of some confusion due to the way different software and different cameras handle rotated images.
Many modern cameras have an orientation sensor built in which can detect when you have rotated the camera 90°. This information is saved along with the image data (as part of the exif data) which can then be read by some (but not all) software, and the image correctly rotated on screen. However when the software does this, it is only rotating it for viewing purposes - the image file remains in landscape. If you want the image to appear correctly rotated in ALL software, you will need to apply a permanent rotation to the image. Some programs can do this by looking at the information stored in the file, rotating the actual image data to reflect this, and then resetting the Exif flag to state that the image no longer needs rotating before viewing.
If the documentation for the software you're using does not make this clear, you may need to do a little bit of experimenting to find out what exactly is going on.
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Orientation: Landscape & Portrait
Landscape and portrait are terms used to describe the orientation of a rectangular page or image. If the page is wider than it is tall, it is said to be landscape. If it is taller than it is wide, it is said to be in portrait (like most books).
The JPEG files stored by your camera are usually in landscape mode, although some modern cameras will flag the image as needing to be rotated before it can be viewed correctly (which some software will then do) - other cameras may actually rotate the image properly rather than just flagging it up. |
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Photographs
This is a site about photography so I'm sure you are expecting to see plenty of pictures.
For now, why not take a peek at the flickr galleries belonging to the two authors of this site.
Colin's Flickr Page
Phil's Flickr Page
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