Photoshop Tutorials Work...Resizing vs. Resampling
Author: DavidPeters Total views: 8 Word Count: 1496
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.
By looking under the Image Menu at the top of the screen, you will find the Image Size dialog box. This option determines resizing or resampling. We mentioned the building blocks of an image before, these are called pixels. How the number of pixels is changed is the difference between resizing and resampling the image. Photoshop refers to this as changing the pixel dimensions. By keeping the number of pixels the same and only changing the size you wish the image to print is called resizing. In Photoshop speak this is termed as changing the document size of the picture. However, if you are actually changing the number of pixels making up the image, it is known as sampling.
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. Alright, now you know the definition of Image resizing and resampling. That's simple enough and don't worry because it really doesn't get much arder to do. You are only a step or two away from doing this with your own images
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
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.
If the Resample Image is unchecked, you will be able to view the number of pixels in both height and width in the Pixel Dimensions portion of the dialog box, but they are visible for information purpose only. You will not be able to change the values of the pixels. The only option available for change is the image print size 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.
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
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.'
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 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.
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