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Although there are those people who would argue, there is a difference between photo resizing and resampling even though both are Photoshop tools designed to change the size of an image. Many people make the mistake of using the two terms interchangeably: however the means by which resizing and resampling is performed is different. The key lies within how the image itself is altered. If this sounds confusing, have heartthe difference between to the two is just one simple checkbox away. Looking at the bottom of the Image Size dialog box, you will see a checkpoint option. This is the option that defines either the resizing or the resampling of the image.

Under the Image Menu at the top of the screen, will be what is called the Image Size dialog box. This again is the one option determining resizing or resampling. An image is actually composed of tiny dots of color together called pixels. How the number of pixels is changed or not changed defines resizing versus resampling the image. Photoshop terminology refers to this as altering the pixel dimensions. Keeping the pixels number the same and only changing the size you wish the picture to print is called resizing. Photoshop refers to this is changing the document size of the image. But, if you in fact change the amount of pixels making up the image, it is known as resampling.

Image Resizing: Changing the size the image will print without changing the number of pixels in the image. Image Resampling: Changing the number of pixels in the image.

It is pretty simple once you know the difference, but how does it relate to your computer and how hard is this to really do? You can do this quickly and easily with your own photos in just a few simple steps

Photoshop’s Image Size dialog box contains some key pieces of information and is separated into two main parts. Pixel Dimensions make up the top half, while the Document Size portion is underneath. Pixel Dimensions shows the width and height consisting of the number of pixels the image is made up of. It also displays the file size of the picture. The Document Size part also shows width and height, but these are the dimensions at which the image will print. The image resolution, also found in the Document Size section of the Image Size box is what these numbers are based from. So remember, he Pixel Dimension will change how an image is displayed on your computer screen or even on the web, whereas changing the Document Size dimensions will affect the print size of the image. Pixel Dimensions = web Document Size = print

Before we begin, it is important to understand what information is contained in the Image Size dialog box. Photoshop’s Image Size dialog box is divided into two main sections. The Pixel Dimensions section is on top, while the ocument Size section is below it. The Pixel Dimensions portion displays the width and height of the image in pixels, and also tells us the file size of our picture. The Document Size section tells how the width and height at which the image is going to print. This is based on the image resolution, also found in the Document Size section of the Image Size box. An easy rule of thumb is that the Pixel Dimension section is what you would change for displaying an image on the web or your computer screen. The Document Size is what you would use to change the dimensions at which the image will print. Pixel Dimensions = web Document Size = print

Also in the Image Size box are three more options below the Document Size section: Scale Styles - Deals with Layer Styles and how they’re affected by resizing or resampling the image. Constrain Proportions - Enabled by default, links the width and height of the image together. If you make a change to the width of the image, for example, Photoshop will automatically change the height, and vice versa, so that the proportions of the image remain the same and don’t get distorted. Resample Image - THE IMPORTANT ONE!!!

We won’t go into detail about the Scale Style and Constrain Proportion, because it is that last box that is the key to resizing vs. resampling. Keep in mind that resizing keeps the pixel dimensions the same and only changes the size at which the image will print, while resampling physically changes the number of pixels in the image. The Resample Image option will be checked by default. This means that even though the dialog box still says ‘Image Size’ at the top, it is now basically the Image Resample dialog box with the checkmark. All of the variables in both the Pixel Dimensions and in the Document Size will be available to you.

The Scale Styles and Constrain Proportions options at the bottom of the Image Size dialog box may or may not be grayed out. When ‘Resample Image’ is unchecked, you will not have access to these options. Scale Styles is grayed out because it’s only used when the number of pixels in an image is being changed. With the number of pixels in the image remaining the same when Resample Image is blank, the Scale Styles is not necessary.

There are also a few other changes that happen depending on if the box is left checked or unchecked. The Scale Styles and Constrain Proportions options at the bottom of the Image Size dialog box are grayed out when Resample Image is not checked. Scale Styles is grayed out because it’s only an issue when the number of pixels in an image is being altered. Since the pixels number of the image remains the same with Resample Image unchecked, the Scale Styles is not needed.

Constrain Proportions is grayed out when Resample Image is unchecked since you no longer have the option of changing the number of pixels in the image. This results in the proportions of the image being fixed. An image is 40 pixels wide and 20 pixels in height, regardless of how large or small it is printed, the width will always be twice the size of the height. If the width value in the Document Size section is changed, both the height and the resolution values will also change. Change the height value and the width and resolution values will change. Change the resolution value, and the width and height values will change. They all work together to adjust the image. The only change that can be made now is how large or small the image will print. You accomplish this by entering new values for the document size or by changing the resolution. The Constrain Proportions option is also not needed when all you are doing is resizing the print size of the image.

Image Interpolation Options When Resampling Images

One more box is grayed out when the Resample Image box is unchecked. To the right of the Resample Image option is a drop-down box called either ‘Bicubic Sharper’ or simply ‘Bicubic.’

Now comes some big words. “Bicubic” and “Bicubic Sharper” are what is called “interpolation algorithms”. All this boils down to is how the hotoshop program handles removing pixels when you resample the image to a smaller size, and how it handles adding pixels when you resample the image to a larger size. In Photoshop CS2, there is another option added called “Bicubic Smoother.” Knowing when to use which option can make a big difference with image quality, but can be remembered with a basic rule as follows: Bicubic Sharper - Use this option when resampling your image smaller for best image quality Bicubic Smoother - Use this option when resampling your image larger for best image quality Bicubic - Not used as much with Bicubic Sharper and Bicubic Smoother being available These options will be grayed out here because they only apply to images that are being resampled. If all you are doing is changing how large or small the image will print on paper, you won’t need these options.

Summary Image resizing - Keeps the number of pixels in your image the same and affects only how large your image will print (the Document Size). Image resampling - Physically changes the number of pixels in your image (the Pixel Dimensions). Resample Image - Option at the bottom of the Image Size dialog box controlling if you are resizing or resampling an image. Checking the Resample Image , you are resampling the image. Unchecked, you’re simply resizing the image. Resample images by changing width and height values in the Pixel Dimensions section of the Image Size dialog box. It is used primarily when optimizing images for the web or computer screen. Resizing images by changing the width, height and/or resolution values in the Document Size section of the Image Size dialog box is used for printing the image.