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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.

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.

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

We’re not quite done yet with the Image Size box. It also contains three other pieces of information as shown below: Scale Styles - Deals with the affect of resizing or resampling the image on Layer Styles. Constrain Proportions - Enabled by default, it 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 - THIS IS THE KEY HERE!!!

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 will touch a bit on Scale Style and Constrain Proportion, but it is that last box being checked or left blank that determines resizing vs. resampling. Remember that resizing keeps the pixel dimensions unchanged and only increases or decreases the size at which the image will print. Resampling however, actually changes the number of pixels in the image. The Resample Image option will be automatically checked by default. Basically, the dialog box still says ‘Image Size’ at the top, but its function now is as the Image Resample dialog box while being checkmarked. All options in both halves, the Pixel Dimensions and the Document Size, will be available to you.

With the Resample Image unchecked, the Pixel Dimensions sector of the dialog box will show how many pixels are in the image for the width and height, but you will no longer be able to change those numbers. They’re visible for information only. The only option available is to change how large the image will print 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.

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.

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.’

Time for the dictionary! “Bicubic” and “Bicubic Sharper” are what is called “iterpolation algorithms”. Don’t worry, simply put, this is what the Photoshop program does in regards to removed pixels when you resample the image to a smaller size, and how it handles added pixels when you resample the image to a larger size. Photoshop CS2 a third option called “Bicubic Smoother.” Image quality can be compromised if you are unsure of which option to use when. Use these basic rules: Bicubic Sharper - Using this option when resampling your image smaller provides best image quality Bicubic Smoother - Using this option when resampling your image larger provides best image quality Bicubic - Typically not used as often being replaced with Bicubic Sharper and Bicubic Smoother

In professional terms, “Bicubic” and “Bicubic Sharper” are what is called “interpolation algorithms”. Before you panic, this just refers to what the Photoshop program does to handle removed 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. Photoshop CS2 a third option called “Bicubic Smoother.” Image quality can be compromised if you are unsure of which option to use when. Use these basic rules: Bicubic Sharper - Using this option when resampling your image smaller provides best image quality Bicubic Smoother - Using this option when resampling your image larger provides best image quality Bicubic - Typically not used as often being replaced with Bicubic Sharper and Bicubic Smoother These options will be grayed out because they only will work for 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.

Last 5 posts by David Peters

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