Get Photoshop…Resizing vs. Resampling
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.
Doesn’t seem like such a big deal now does it? The difference is pretty simple once explained just a bit. But how do you actually do this with your own photos? Let’s walk through the steps
Resizing vs. Resizing An Image
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
The Image Size box also contains a few more bits of information. You will find 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 will not distort. Resample Image – THIS IS WHAT YOU HAVE BEEN WAITING FOR!!!
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.
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.
Image Interpolation Options When Resampling Images
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
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 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.