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Queen's University

Fall 2010 Newsletter

Size Does Matter: How to Resize Images in Photoshop

Did you know? If you took 32 pictures with a 10 megapixel camera they would have a resolution of 3648 pixels (px) by 2736 px and these pictures would take up approximately 110 megabytes (MB). If these same pictures were reduced to 1024 px by 768 px, they would only take up 17.5 MB. Reducing them further to 500 px by 375 px would result in the pictures only taking up 5.5 MB. Because most people's monitors are not set higher than 1024 px by 768 px, there is always a need to reduce pictures you wish to display on the web, include in a document or send in email to a friend. Your friends will be appreciative that you took the time to reduce large pictures before attaching them to email messages. Follow these steps for reducing the size of a graphic or picture in Photoshop.


Image showing the instruction to open a file in Photoshop by clicking on the File menu followed by the menu item Save for Web Devices screen

Step 1: Open the file in Photoshop

Open the file in Photoshop by clicking on the File tab followed by the "Save for Web Devices..." as illustrated in the image to the right. 


If the Save for Web & Device warning box appears, informing you that the image exceeds the size allowed, as illustrated in the image below, just click on the Yes button to continue.


Image of the Image too large warning box asking the viewer to click the yes button to continue.




Image showing configurable settings on the Save for Web and Devices Screen including the file type, quality, optimization and size of image

Step 2: Select Settings on the Save for Web & Devices Screen


As you select and change settings, which are numbered 1-4 in the image to the right, monitor the areas on the image marked as the letters A and B.  The letter A area is a visual representation of the picture you wish to reduce. As you turn down the quality, you can see what effect it will have on your picture and what the image file size will be (the area box marked as the letter B).


Settings numbered 1-5 on the image:


1. Number 1 refers to file type. Select the file type you would like to use. If you are unsure select JPEG.


2. Select the amount of quality that works best for you. If you are unsure select "Very High". The higher the quality the larger the image file size (monitor box B below the image).


3. For the most part this can be left at optimize. If you are saving the
picture for use on the web and if you know that people will be viewing your image via slow connections (or on dial up) you may want to select progressive. 


4. Select the image size, keeping in mind that most people's monitors are not set higher than 1024 px by 768 px. If you are putting the picture on a web page, find out exactly how much space you have for the picture. If you are emailing pictures to friends and family, keep the image size around 500 px by 375 px, especially if you are emailing pictures. 


5. Save your new reduced picture under a new name.


If you have a lot of pictures that you want to re-size you can also reduce them "all at once" in Photoshop. Watch for these steps in the next issue of the ITServices newsletter.


Don't have Photoshop? Students, staff and faculty are all welcome to use the computers in the Emerging Technology Centre (ETC) free of charge. The entire Adobe CS5 collection, including Photoshop, has been installed on all of the machines in the ETC.


Glossary of Terms for the Novice


Megabyte: Used to specify multiples of the unit "byte" for measurement. The most common definition of the term is 1,048,576 bytes (1024*1024 bytes). A few standards authorities (IEC, IEEE, etc.) have proposed the use of the term "Mebibyte" to denote 1024*1024 bytes, with the term "Megabyte" being defined as 1,000,000 bytes (1000*1000). However, the term "Mebibyte" to refer to 1024*1024 bytes is not in common usage and has lead to some confusion. If you are stimulated by discussion regarding the use of Megabyte to refer to two different context-based values (historically, there are three), you can view the  shared meanings of the term Megabyte on its WikiPedia web page.


Megapixel Camera: Refers to 1 million pixels in a digital camera.


Pixel: A pixel is the smallest visual element on your computer screen. The word "pixel' was created from the phrase, "picture element", using the term "pix" for picture and "el" for element.












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