Learn Photoshop...resizing Vs. Resampling

Contrary to what you may think, there is a difference between photo resizing and resampling although both are tools used to change the size of an image in Photoshop. Many people might believe the two terms are basically interchangeable; however how the result is accomplished is different in how it changes the building blocks of the image itself. Although this may sound drastic, the difference between to the two is all in one simple click. At the bottom of the Image Size dialog box, there is a checkpoint option that creates either the resizing or resampling of the image.

The top of the screen has the Image Menu, under this option will be what is called the Image Size dialog box. Here you will find the checkpoint determining resizing or resampling function. Pixels are the tiny dots of color that when grouped together form the image. Resizing or resampling the image happens depending on is the number f pixels changes or not. In Photoshop this is called changing the pixel dimensions. Changing only the size you wish the picture and eaving the pixel number the same is called resizing. Photoshop calls this changing the document size of the image. Changing the number of pixels making up the image is referred to 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.

Resizing vs. Resampling An Image

Let's first take a look at what information the Image Size dialog box contains. Photoshop's Image Size dialog box is separated into two main parts. The Pixel Dimensions section is the top half, while the Document Size section is the bottom half. The Pixel Dimensions part shows the width and height of the image in the number of pixels it is made up of. It also tells us the file size of the picture. The Document Size half displays the width and height at which the image will print. This is based on the image resolution, also found in the Document Size section of the Image Size box. A simple way to remember the difference in applications is that the Pixel Dimension will change how an image is displayed on your computer screen or even on the web. Changing the Document Size dimensions will effect the print size of the image. 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!!!

If unchecked, the Resample Image will only display the number of pixels or both the height and width in the Pixel Dimensions blocks of the dialog box, but they are visible just for information purposes. The pixels values will not be able to be changed. Only the image print size can be changed by using the Document Size section. With Resample Image checked, the pixel dimensions are shown inside white input boxes which we can click inside of and type in new values, changing how many pixels are in our image.

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.

You will find that Constrain Proportions is also grayed out when Resample Image is unchecked. Again you will not have the option of changing the number of pixels in the image. This selection results in the proportions of the image being fixed. If an image is 30 pixels wide and 60 pixels igh, no matter the size it is printed, the height will always be twice he size of the width. 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 as a function. The only change that can be made ow is how large or small the image will print. Simply entering new values for the document size or by changing the resolution will do this. The onstrain Proportions option is also not needed when all you are doing is resizing the print size of the image.

Constrain Proportions is also grayed out when Resample Image is unchecked. This is because there will not be the option of changing the number of pixels in the image either. This option results in the proportions of the image being fixed. An image is 100 pixels wide and 50 pixels in high, no matter the size 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 together. The only change that can be made now is how large or small the image will print. Simply entering new values for the document size or by changing the resolution will do this. The Constrain Proportions option is also not needed when all you are doing is resizing the print size of the image.

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.'

There is one more box that 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 the image will print (the Document Size). Image resampling - Physically changes the number of pixels in the image (the Pixel Dimensions). Resample Image - Option located at the bottom of the Image Size dialog box that controls if you are resizing or resampling the image. Checking the Resample Image, means 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 mostly 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.