You can resize images in several ways using Adobe Photoshop and Adobe Photoshop Elements. Each way to resize an image has advantages and drawbacks. To get the best result when you resize images, you should understand the concepts behind and the results of each method of resizing. These concepts affect how the crop tool options operate as well. If you resize and crop images without being aware of the concepts involved, then you may see unexpected results.
Image sizes on the screen and in print
The size of an image when you view it on the screen is different from the size of an image when you print it. If you understand these differences, then you can develop a better understanding of which settings to change when you resize an image.
Screen size
The screen resolution of your monitor is the number of pixels that your monitor can display. For example, a monitor with a screen resolution of 640x480 pixels will display 640 pixels for the width and 480 pixels for the height. There are several different screen resolutions you can use, and the physical size of the monitor screen usually determines the resolutions available. For example, large monitors typically display higher resolutions than small monitors because they have more pixels.
To find out what your screen resolution is, choose Start > Control Panel > Display > Settings and look at the screen resolution (Windows) or System Preferences > Displays and look in the resolution section (Mac OS).
Image size on the screen
Images are of a fixed pixel size when they appear on your monitor. Your screen resolution determines how large the image appears to be. A monitor set to 640x480 pixels displays fewer pixels than a monitor displaying 1024x768 pixels, so each of the pixels on the 640x480 pixel monitor will be larger than each of the pixels displayed on the 1024x768 pixel monitor.
An image of 100x100 pixels will take up approximately 1/6 of the screen at 640x480, but it will only take up approximately 1/10 of the screen at 1024x768, so the image will look smaller at 1024x768 pixels than at 640x480 pixels.
Image size in print
The other values used in resizing images, the physical size of the image when printed, and the resolution (the number of pixels per inch), aren't used in calculations until the image is printed. When you go to print, the physical size of the image, the resolution, and the pixel dimensions interact to determine the amount of data in the image and its print quality. In general, higher resolution images print at a higher quality. See the sections that follow for more information on resolution and physical size in the below sections.
Image Size dialog box
When you use the Image Size dialog box to resize your images, or when you use the Crop tool options bar to crop, and consequently resize, your images, four aspects of your image can change:
- the pixel dimensions, which is the width and height of the image in pixels - in the Pixel Dimension section
- the file size of the image when it's open in Photoshop - in the Pixel Dimension section
- the physical size of the image when printed, in width and height - in the Document Size section
- the resolution of the image when printed (the amount of data in the image for printing), which is the number of pixels per inch or per centimeter - in the Document Size section. The resolution is the amount of detail in the image.
Note: See the Image size formulas section of this document for some simple formulas you can use to understand how Photoshop and Photoshop Elements determine the size of an image.
The Image Size dialog box allows you to resize your images in two ways: by increasing or decreasing the amount of data in the image (resampling) or by maintaining the same amount of data in the image (referred to in this document as resizing without resampling). When you resample, the image quality may degrade to some extent and you may have to do some extra work afterward to compensate for the results, such as using the Unsharp Mask filter to sharpen your image.
To reset the Image Size dialog box to its original state, the Cancel button can be changed to a Reset button by holding down the Alt (Windows) or the Option (Mac OS) key.
The above taken from the Adobe Photoshop Support Pages - Click HERE to access full information on the Adobe site.
